Three-dimensional model recovery from two-dimensional images

A three-dimensional (3D) model of an object is recovered from two-dimensional (2D) images of the object. Each image in the set of 2D images includes the object captured from a different camera position and deformations of a base mesh that defines the 3D model may be computed corresponding to each image. The 3D model may also include a texture map that represents the lighting and material properties of the 3D model. Recovery of the 3D model relies on analytic antialiasing to provide a link between pixel colors in the 2D images and geometry of the 3D model. A modular differentiable renderer design yields high performance by leveraging existing, highly optimized hardware graphics pipelines to reconstruct the 3D model. The differential renderer renders images of the 3D model and differences between the rendered images and reference images are propagated backwards through the rendering pipeline to iteratively adjust the 3D model.

BACKGROUND

Inverse rendering is a technique used to iteratively recover a shape, lighting, and material properties of a 3D model based on 2D images. Inverse rendering is challenging because the operations used to render the 3D model to produce the 2D images cannot simply be performed in reverse to generate the 3D model from the 2D images. Conventional inverse rendering techniques typically focus on either image quality or performance. There is a need for addressing these issues and/or other issues associated with the prior art.

SUMMARY

Embodiments of the present disclosure relate to three-dimensional (3D) model recovery from two-dimensional (2D) images. Systems and methods are disclosed that enable recovery of a 3D model of an object from a set of 2D images of the object. Each image in the set of 2D images includes the object captured from a different camera position. The 3D model that is recovered may be represented as a single base mesh defined by vertices corresponding to locations in 3D space. Deformations of the 3D model may be computed corresponding to each image. In an embodiment, the deformations are offsets for the vertex locations. The 3D model may also include a texture map that represents the lighting and material properties of the 3D model. Recovery of the 3D model relies on analytic antialiasing to provide a link between pixel colors in the 2D images and geometry of the 3D model.

A method, computer readable medium, and system are disclosed for constructing a 3D model from 2D images. An image of the 3D model defined by initial geometry is rendered, where an antialiasing operation performed by a rendering pipeline processes data associated with the geometry to antialias the image and pixel differences are computed based on the image and a reference image. The pixel differences are propagated backwards through the antialiasing operation of the rendering pipeline to compute geometry changes corresponding to reducing the pixel differences and the initial geometry is adjusted based on the geometry changes to produce modified geometry defining the 3D model.

DETAILED DESCRIPTION

Systems and methods are disclosed related to 3D model recovery from 2D images. A modular differentiable renderer design yields high performance by leveraging existing, highly optimized hardware graphics pipelines to reconstruct the 3D model. In an embodiment, one or more operations of the differentiable renderer are performed using any combination of a graphics processing unit (GPU) graphics pipeline, GPU general computation cores, or on a central processing unit (CPU). The differentiable renderer enables operations such as rasterizing large numbers of triangles, attribute interpolation, filtered texture lookups, as well as user-programmable shading and geometry processing, all in high resolutions. In contrast with conventional systems, the recovered 3D model is accurate and may be generated by rendering analytically antialiased images of the 3D model and propagating differences between the rendered images and reference images backwards through the rendering pipeline to iteratively adjust the 3D model.

FIG.1Aillustrates a conceptual diagram of a 3D model recovery system100, in accordance with an embodiment. A set of 2D images of an object110are captured from a variety of camera positions. The 3D model recovery system100constructs a 3D model130of the object using the set of 2D images to refine an initial 3D model. The initial 3D model may be a sphere or other geometric shape. In an embodiment, the 3D model130is a base model that is deformed to produce a specific 3D model corresponding to each of the 2D images in the set. In another embodiment, a complete 3D model130is constructed for each of one or more of the 2D images in the set. A set of texture maps125is global surface texture defining lighting and materials properties120that may be applied to the 3D model130. In an embodiment, the set of texture maps125comprises a mip mapped texture. An initial global surface texture may be a constant color and the colors of each texel in the initial global surface texture are adjusted by the 3D model recovery system100to produce the set of texture maps125.

The goal of the 3D model recovery system100is to produce the 3D model130that, when rendered using the set of texture maps125produces rendered images that closely match the set of 2D images of the object110. The camera positions associated with the set of 2D images of the object110are used by the 3D model recovery system100to render the 3D model130. Unlike conventional rendering systems having a goal of rendering high quality images, the 3D model recovery system100utilizes rendering to enable recovery of the 3D model130. In other words, the rendered images are processed to determine and fine-tune the geometry that defines the 3D model. In an embodiment, the geometry is defined by locations of vertices that form a mesh of the 3D model130. In an embodiment, the mesh is defined by other types of primitives or representations. In an embodiment, the set of 2D images of the object110comprise a video.

Recovery of the 3D model130may be used to perform markerless facial performance capture. Markerless means that there are no landmark points marked onto the object in the set of 2D images of the object110. The recovery process constructs the 3D model130reproducing facial expressions visible in the different 2D images. 3D model recovery enables generation of new images of the 3D model for character animation, such as during gameplay or for film production.

FIG.1Billustrates another conceptual diagram of a 3D model recovery system100, in accordance with an embodiment. The 3D model recovery system100receives an initial 3D model132of an object and an initial global texture (not shown). In an embodiment, texture coordinates of the initial 3D model132are associated with each vertex defining the initial 3D model132and the association between the vertices and texture coordinates is unchanged even when locations of the vertices are modified to produce the constructed 3D model134. However, contents of the global texture are adjusted as the constructed 3D model134is modified.

The 3D model recovery system100also receives the set of 2D images of an object110, that may include the reference image112. As previously described, the goal of the 3D model recovery system100is to find a global texture and a constructed 3D model134(e.g., per-image mesh), that when rendered from a camera position114associated with the reference image112, produce a rendered image115that matches the reference image112. In an embodiment, the 3D model recovery system100compares the reference image112and the rendered image115, determining differences and computes an image-space loss. The image-space loss is then propagated backwards through the rendering operations to adjust the initial 3D model132and produce the constructed 3D model134. In contrast with conventional rendering systems that are configured to produce images from 3D geometry, the 3D model recovery system100includes a differentiable rendering pipeline. The differentiable rendering pipeline can produce images from 3D geometry in a forward operating mode and can also reconstruct 3D geometry from images in a backward operating mode. The rendering and backwards propagation may be repeated for several different reference images to iteratively adjust the initial 3D model132, deforming the initial 3D model132to correspond to the individual reference images.

In the context of the following description, the rendered image115and other images rendered by the 3D model recovery system100are antialiased images, where the antialiasing operation processes geometry data (e.g., vertex locations or primitives) associated with the initial 3D model132or base mesh to antialias the image. In an embodiment, the antialiasing operation is an analytic antialiasing operation that determines shaded pixel values based on geometric coverage after rasterization, visibility testing, and texture mapping is performed.

FIG.1Cillustrates a conceptual diagram of analytic antialiasing, in accordance with an embodiment. Rendered geometry136forms a silhouette edge138of an object that is closer to the camera compared with the background or another surface that is obscured by the object. In an embodiment, an edge forms a silhouette if it has only one connecting triangle, or if it connects two triangles with the same winding (indicating both triangles are either front-facing or back-facing). In an embodiment, an edge forms a silhouette if the triangles connecting to the edge lie on the same side of the edge, as seen from camera, regardless of the winding.

Silhouette edges provide useful information needed to accurately recover a 3D model of the object because the shape of the object in the image plane can be extracted and, in combination with the camera position, can be used to adjust the geometry (e.g., vertex locations) for the 3D model. Thus, each reference 2D image and corresponding rendered analytic antialiased image, as described further herein, provides additional information that is used to improve the 3D model.

Each of pixels135and140includes a single sample at the center of the pixel. Conventionally, rendered geometry136is visible in pixel135and is not visible in pixel140because the sample in the pixel135is covered by the rendered geometry136and the sample in pixel140is not covered. Thus, when shaded, pixels135and140appear as shaded pixels141and142. The shaded pixels141and142appear the same for many different positions and orientations of the edge138. Notably, the shaded pixels141and142only provide enough information to know that an intersection137of the edge138is somewhere along a horizontal segment between the two samples of135and140. The transition as the sample in pixel140is covered or uncovered is sudden and discontinuous rather than smooth or gradual and does not precisely represent the rendered geometry136.

Instead of simply relying on whether samples are covered or not to compute the shaded pixels, analytic antialiasing uses the geometric data, particularly the edge138and intersection137, to compute shaded pixels143and144. As shown inFIG.1C, pixel144is shaded corresponding to being partially covered by the rendered geometry136. As the intersection137moves closer to the sample in pixel140, a contribution to the shaded value of shaded pixel144from the rendered geometry136increases. Conversely, as the intersection137moves further from the sample in pixel140, the shaded value the contribution to the shaded value of shaded pixel144from the rendered geometry136decreases. The same information that is used to determine the contribution of rendered geometry136to the shaded pixels143and144in image space may be used working backwards to compute gradients of vertex positions in 3D model space. Just as the analytic antialiasing produces a more accurate image in terms of object visibility, the corresponding vertex gradients provide more accurate adjustments to the 3D model.

In an embodiment, the edge138passes between centers of horizontally adjacent pixels135and140and is detected by the pixels135and140having a different triangle identifier (ID) rasterized into them. Pixels135and140may be processed together as a pair, and one of the following cases may occur. (a) The edge138crosses the segment connecting pixel centers at the intersection137inside pixel140, causing color of pixel135to blend into pixel140. (b) The crossing happens inside pixel135, so blending is done in the opposite direction. To approximate the geometric coverage between surfaces, the blending factor is a linear function of the location of the crossing point—from zero at midpoint to 50% at pixel center. This particular analytic antialiasing method is differentiable because the resulting pixel colors are continuous functions of positions of vertices of the rendered geometry136. In an embodiment, a more complex calculation can be performed to determine the blending factor, considering, e.g., the orientation, length, and location of endpoints of edge138, to more accurately estimate how much the rendered geometry136covers pixel140. In an embodiment, multiple edges may be considered when determining the blending factor. In an embodiment, multiple blending factors may be determined to enable blending between more than two pixels.

FIG.1Dillustrates another conceptual diagram of analytic antialiasing, in accordance with an embodiment. Rendered geometry146forms a silhouette edge148of an object. Each of pixels145and150includes a single sample at the center of the pixel. Conventionally, rendered geometry146is visible in pixel145and is not visible in pixel150because the sample in the pixel145is covered by the rendered geometry146and the sample in pixel150is not covered. Thus, when shaded, pixels145and150appear as shaded pixels151and152. Using conventional rasterization (one sample per pixel, or even multiple samples per pixel) without analytic antialiasing, the visibility (i.e., which geometry is visible in each pixel) is discontinuous and piecewise constant—moving any vertex or the edge148by an infinitesimal amount will not change which pixels (or samples) that the rendered geometry146covers.

In contrast, analytic antialiasing uses the edge148and intersection147, to compute shaded pixels153and154. An intersection147is inside pixel145, causing color of pixel150to blend into pixel145. As shown inFIG.1D, pixel153is shaded corresponding to being partially covered by the rendered geometry146and pixel154is not shaded because the rendered geometry146does not intersect the pixel150.

Analytic antialiasing approximates the pixel integral (average surface color inside the pixel) based on the location of a silhouette edge in the pixel. The output color of the pixel depends—among other things—on the positions of the vertices that define the silhouette edge in the pixel. In particular, the intersection of the segment between pixel pairs for different triangle IDs. The dependence is (piecewise) continuous and therefore differentiable, and thus the gradients of the vertex positions will also reflect the change in the output pixel color due to a change in how much the closer rendered geometry defining the silhouette edge covers the pixel. The gradients will therefore contain information on how moving the vertices affects the location of the silhouette edge in the rendered image. As shown inFIGS.1C and1D, as the silhouette edge of the rendered geometry moves closer towards or further away from the pixel center, the color of the pixel changes. Thus, changes in the pixel color provide information about the vertex positions. In contrast, when conventional rasterization is used, the color of the pixel changes only when the center is covered or uncovered, so very little information about the vertex positions may be determined from the color. Therefore, if the silhouette edge of a conventionally rendered 3D model is in a wrong location in image space, there is little or no information based on which vertices of the 3D model can be adjusted so that the silhouette edge appears closer to where it should be in the rendered image.

The 3D model recovery technique may use the analytic antialiasing to recover not only a shape of the object, but also lighting, and material properties of the 3D model given the set of 2D images of the object. Analytic antialiasing is included in a differentiable rasterization pipeline that performs deferred shading to render the 3D model to produce the rendered images for each camera position associated with the 2D images. Specifically, analytic antialiasing is performed on the output of the deferred shading operation, receiving shaded pixels and, taking as additional inputs, data for the geometry, triangle IDs, and vertex positions and indices.

Analytic antialiasing may be implemented by first detecting potential visibility discontinuities by finding all neighboring horizontal and vertical pixel pairs with mismatching triangle IDs. For each potential discontinuity, the triangle associated with the surface closer to camera, as determined from the normalized device coordinate (NDC) depths computed during rasterization, is fetched. Then the edges of the triangle are examined to determine if any of the edges form a silhouette and pass between the pixel centers of the pixel pairs. For horizontal pixel pairs, only vertically oriented edges (|wc,1·yc,2−wc,2·yc,1|>|wc,1·xc,2−wc,2·xc,1|) are considered, and vice versa, where (x, y, w) are the x, y pixel coordinates in clip space. If a silhouette edge crosses the segment between pixel centers, a blend weight is computed by determining the intersection point where the crossing occurs. Pixel colors are then adjusted to reflect the approximated coverage of either surface in the pixels. The technique essentially approximates the exact surface coverage per pixel using an axis-aligned slab. Consequently, the coverage estimate is exact for only perfectly vertical and horizontal edges that extend beyond the pixel. However, the coverage estimate is an adequate enough approximation for other (non-vertical, non-horizontal) intersections for the purposes of recovering an accurate 3D model. In an embodiment, the more complex calculation can be performed to determine the blending factor, considering, e.g., the orientation, length, and location of edge endpoints.

Given a 3D scene description in the form of geometric shapes, materials, and camera and lighting models, rendering 2D images boils down to two computational problems: figuring out which portions of the 3D scene that are visible in each pixel, and what color the visible portions appear to be. A proper differentiable renderer has to provide gradients for all the parameters—e.g., lighting and material parameters, as well as the contents of texture maps—used in the process. In the context of the following description, it is useful to break the rendering process down into the following form, where the final color Iiof the pixel at screen coordinates (xi, yi) is given by

Here, P(x, y) denotes the world point visible at (continuous) image coordinates (x, y) after projection from 3D to 2D, and M(P) denotes all the spatially-varying factors (texture maps, normal vectors, etc.) that live on the surfaces of the scene. The shade function typically models light-surface interactions. The 2D antialiasing filter, crucial for both image quality and differentiability, is applied to the shading results in continuous (x, y), and the final color is obtained by sampling the result at the pixel center (x, y).

The 3D model recovery system100includes a 3D model construction unit200, a differentiable renderer215, and an image space loss unit245. The differentiable renderer215includes a rendering pipeline205and a backpropagation pipeline260. A 3D model is rendered from a camera position in a forward pass through the rendering pipeline205of the differentiable renderer215to produce an antialiased image. The 3D model construction unit200provides a representation of the 3D model to the rendering pipeline205along with a reference camera position. In an embodiment, an initial 3D model may be a base mesh that is as simple as a cube or sphere. In an embodiment, the 3D model comprises vertices in 3D model space and attributes associated with the vertices. An initial surface texture map corresponding to the initial 3D model may be a uniform color.

The rendering pipeline205processes the 3D model performing steps of transform (from 3D to 2D), rasterization, interpolation, texture lookup, and antialiasing. A last stage in the rendering pipeline205performs analytic antialiasing to compute visibility-related effects of geometric edges on the rendered image. When performed in reverse by the backwards propagation pipeline260, the analytic antialiasing operation determines how the gradient of pixel colors transfers to the gradient of the 3D model.

The image space loss unit245determines an image space (color) loss based on per-pixel color differences between the antialiased image and a reference (target) image of the object associated with the reference camera position. The differences quantify the accuracy of the 3D model of the object and represent a “loss”. In an embodiment, the differences are computed as a mean square per-pixel difference. In an embodiment, the differences are computed between high-dimensional embeddings of the images, e.g., computed using pre-trained neural networks. The image space loss penalizes 3D model solutions where the rendering does not match the reference image. However, the image space loss unit245may use other loss functions along with the image space loss to regularize the optimization. In an embodiment, a Laplacian loss penalizes solutions where the curvature of the mesh changes severely compared to the base mesh, effectively encouraging the optimization to only consider solutions that are physically plausible.

The backwards propagation pipeline260receives antialiased image gradients that indicate how the color of each pixel of the antialiased image affects the loss. The backwards propagation pipeline260computes (1) gradient of the aliased image that is input to the last stage of the rendering pipeline205(analytic antialiasing), and (2) gradient of the vertex positions. The forward rendering, comparison with a reference image, and backwards propagation are performed for multiple camera positions to produce a surface texture map and geometry for a modified version of the initial 3D model or base mesh for each reference image. The result is a 3D model of the object and corresponding surface texture map that, when rendered, match the target images. Using multiple camera positions enables the recovery of different portions of the object through the analytic antialiasing due to the variety of silhouette edges that are rendered.

In an embodiment, the texture map values (e.g., texture map coordinates and texels) and vertex positions are latent variables that can be optimized to reduce the loss, thereby improving accuracy of the 3D model. Determining how to change the latent variables to accomplish the reduction of loss is performed using backpropagation. When propagating antialiased image gradients through the backwards propagation pipeline260, the gradient of the output for each computation step is known (i.e., how changes in the output values of each computation step will affect the loss), so that the gradients of the inputs to the computation step may be determined (i.e., how changes in the input values of each computation step will affect the loss). Parameters computed by each step during the forward propagation through the rendering pipeline105may be provided to the backwards propagation pipeline260for computing corresponding per-stage gradients.

After the antialiased image gradients are backwards propagated through the entire backwards propagation pipeline260, it is possible to quantify how changing the latent variables affects the loss, and the latent variables can be adjusted in the direction that should reduce the loss. The visibility-related 3D model gradients that are computed during backpropagation indicate the effect that moving the vertex positions has on the antialiased image due to changes in fractional pixel coverage. The 3D model construction unit200receives the 3D model gradients and adjusts the 3D model to reduce the loss.

Applying Equation (1) to the differentiable rendering, the geometry, projection, and lighting can all be considered as parametric functions. The visible world point is affected by the geometry, parameterized by θG, as well as the projection, parameterized by θC. Similarly, the surface factors are parameterized by θM, and light sources by θL. In the simplest case, θGand θM, could describe, say, the vertex coordinates of a triangle mesh of a fixed topology and a diffuse albedo stored at the vertices and interpolated into the interiors of triangles. In an embodiment, the 3D model representation is a complex parameterization that is computed by a deep learning model within the 3D model construction unit200and input to the differentiable renderer115. In the context of the following description, differentiable rendering comprises computing the gradients ∂L(I)/∂{θG, θM, θC, θL} of a scalar function L(I) of the rendered image I with respect to the scene parameters. Note that this does not require computing the (very large) Jacobian matrices [∂I/∂θG], etc., but rather only the ability to implement multiplication with the Jacobian transpose (“backpropagation”), yielding the final result through the chain rule:

[∂L⁡(I)∂θG]=[∂I∂θG][∂L∂I],
and similarly for the other parameter vectors.

Two main factors make the design of efficient rendering algorithms challenging. First, the mapping P(x, y) between 3D model or world space points and screen or image coordinates is dynamic: it is affected by changes in both scene geometry and the 3D-to-2D projection. Furthermore, the mapping is discontinuous due to occlusion boundaries. These two factors are also central points of difficulty in computing the gradients by the backwards propagation pipeline260.

The differentiable renderer215may render, in high resolution, 3D scenes that are complex in terms of geometric detail, occlusion, and appearance. In an embodiment, the rendering is performed in real-time and the stages in the pipelines parallelize processing over both the geometric primitives and pixels. In an embodiment, the differentiable renderer215comprises modular, configurable, and programmable stages to enable easy construction of potentially complex custom rendering pipelines. In an embodiment, the differentiable renderer215takes the input geometry and texture maps (e.g., 3D model) in the form of tensors allowing parameterizing both in a freely-chosen manner, and enabling the rendering primitives to be used as building blocks of a complex learning system.

The differentiable renderer215performs deferred shading, first computing, for each pixel, the M(P(x, y)) terms from Equation (1) and storing the intermediate results in an image-space regular grid. The grid is subsequently consumed by a shading function to produce a shaded output grid that is input to the analytic antialiasing filter in Equation (1). Effectively, shading is assumed to be constant with respect to the coverage effects at silhouette boundaries, but not with respect to other effects in appearance.

FIG.2Billustrates another block diagram of another example 3D model recovery system100suitable for use in implementing some embodiments of the present disclosure. The differentiable rendering pipeline205includes a vertex transform unit210, rasterizer220, interpolation unit230, texture lookup240, and analytic antialias unit250. In an embodiment, the differentiable rendering pipeline205also includes the backwards propagation pipeline260. The details of the backwards propagation pipeline260are shown inFIG.2C. In an embodiment, the differentiable rendering pipeline205and the backwards propagation pipeline260are combined and the operations performed by the backwards propagation pipeline260are performed by a combination of the vertex transform unit210, rasterizer220, interpolation unit230, texture lookup240, analytic antialias unit250.

The 3D model construction unit200adjusts the 3D model for each iteration of the differentiable renderer215. In an embodiment, the 3D model construction unit200comprises a “deformation network” that takes in a base mesh and frame index representation of the 3D model, and outputs the vertex positions to render an antialiased image for a reference camera position. The deformation network is not necessarily a general-purpose neural network, but it may learn more efficiently (i.e., is more amenable to optimization) than having an array of vertex positions separately for every frame. The 3D model construction unit200also adjusts the global surface texture for each iteration of the differentiable renderer215. As shown inFIG.2B, the 3D model that is output to the vertex transform unit210comprises vertices and attributes in 3D model space.

The vertex transform unit210performs world, view, and homogeneous perspective transformations, to produce transformed vertices that are output to the rasterizer220. The rasterizer220performs perspective division and implements dynamic mapping between world coordinates and discrete pixel coordinates. Per-pixel auxiliary data may be stored in the form of barycentric coordinates and triangle IDs in the forward pass through the rendering pipeline205. Using barycentrics and NDC depth (u, v, zc/wc) as a base coordinate system allows easy coupling of shading and interpolation, as well as combining texture gradients with geometry gradients in the backward pass through the backwards propagation pipeline260.

In an embodiment, the rasterizer220consumes triangles with vertex positions given as an array of clip-space homogeneous coordinates (xc, yc, zc, wc). The backwards propagation pipeline260then computes the gradient ∂L/∂{xc, yc,zc,wc} of the loss L with respect to the clip-space positions. Differentiation with respect to any higher-level parameterizations may be performed outside of the 3D model recovery system100.

In the forward pass through the rendering pipeline205, the rasterizer220outputs a 2D sample grid associated with the image being rendered, with each position storing a tuple (ID, u, v, zc/wc), where ID identifies the triangle covering the sample, (u, v) are barycentric coordinates specifying relative position along the triangle, and z/w corresponds to the depth in normalized device coordinates (NDC). In an embodiment, a special ID is reserved for blank pixels. Barycentric coordinates serve as a convenient base domain for interpolation and texture mapping computations for downstream stages in the rendering pipeline205. In an embodiment, the NDC depth is utilized only by the subsequent analytic antialias unit250, and does not propagate gradients. In an embodiment, the rasterizer220outputs a secondary output buffer with the 2×2 Jacobian of the barycentrics w.r.t. the image coordinates ∂{u, v}/∂{x, y} for each pixel. The secondary output buffer may be used by the interpolation unit230to compute image space derivatives of texture coordinates, which in turn may be used by texture lookup240for determining the texture footprints for filtered texture lookups.

Within the rasterizer220, the rasterization may performed through OpenGL, leveraging a hardware graphics pipeline. Using the hardware graphics pipeline ensures that the rasterization is accurate and there are, e.g., no visibility leaks due to precision issues. Additionally, using the hardware graphics pipeline automatically provides proper view frustum clipping. The per-pixel 2×2 Jacobians between barycentrics and image coordinates may be obtained from the OpenGL fragment shader, computed by finite differences in a 2×2 pixel quad. Alternatively, the per-pixel 2×2 Jacobians may be computed analytically for each pixel.

The interpolation unit230expands per-vertex data (i.e., vertex attributes) to pixel or image space, producing interpolated attributes. Making use of the barycentrics computed by the rasterizer220, the interpolation unit230accomplishes the mapping in the forward direction and the barycentrics may also be used by a corresponding interpolation operation in the backwards propagation pipeline260to map from image space to NDC space.

Attribute interpolation is a standard part of the graphics pipeline. Specifically, it entails computing weighted sums of vertex attributes, with weights given by the barycentrics, thereby creating a mapping between the pixels and the attributes. Generally, vertex attributes can be used for arbitrary purposes. One of typical use, however, is to provide 2D coordinates for texture mapping. In addition to its general operation, the interpolation unit230provides special support for computing, in the forward pass, image space derivatives of texture coordinates that may be used later by the texture lookup240in determining MIP-map filter footprints.

The interpolation unit230receives a vector of attributes Aiassociated with the ith vertex, where the attribute indices of the triangle visible in the pixel (x, y) are i0,1,2, and the barycentrics generated by the rasterizer220are u=u(x, y) and v=v(x, y). The interpolated vector A is defined as
A=uAi0+vAi1+(1−u−v)Ai2.   Eq. (2)

Given the rasterizer's outputs (per-pixel triangle IDs and barycentrics), implementation of the forward pass is straightforward. The image space derivatives for attributes tagged as requiring derivatives are computed using the barycenter Jacobians output by the rasterizer by

∂A∂{x,y}=[∂{u,v}∂{x,y}][∂A∂{u,v}],
where the last Jacobian is simple to derive from Equation (2).

The texture lookup240receives the interpolated texture coordinate attributes and image space derivatives of the texture coordinate attributes and reads texels from the global surface texture stored in the 3D model construction unit200. The texels and image space derivatives are used by the texture lookup240to produce shaded pixels. Gradients may be correctly propagated backwards by the backwards propagation pipeline260through both input texture coordinates as well as the contents of the (MIP-mapped) texture map.

When the texture lookup240performs texture mapping using trilinear MIP-mapped texture fetches, a (continuous) MIP-map pyramid level (i.e., level-of-detail, LOD) is selected based on the incoming image space derivatives of the texture coordinates. Then a trilinear interpolation is performed using the eight nearest texels from the pair of appropriate MIP pyramid levels. The MIP level may be selected based on the texture space length of the major axis of the sample footprint defined by the derivatives. In an embodiment, the MIP level is computed by the interpolation unit230as a part of the interpolation operation, where the necessary data is readily available. In an embodiment, the texture lookup240may be configured to perform texture mapping using bilinear, point sampled, or other types of MIP-mapped or non-MIP-mapped texture fetches.

An image comprising the shaded pixels output by the texture lookup240does not exhibit aliasing within surface (inside of rendered geometry). However, point-sampled visibility causes aliasing at visibility discontinuities, and more crucially, cannot produce visibility-related gradients for adjusting vertex positions of the 3D model. The analytic antialias unit250converts the discontinuities to smooth changes from which the gradients can be computed. Note that antialiasing can only be performed after shading, and therefore must be implemented as a separate stage of the rendering pipeline205instead of being performed as part of rasterization.

The analytic antialias unit250receives the shaded pixels resulting from deferred shading, transformed vertices, triangle IDs, and depth (zc/wc) and outputs an antialiased image. The analytic antialias unit250detects the visibility discontinuities and associated with vertex positions, as needed to compute gradients. In an embodiment, potential visibility discontinuities are detected by finding all neighboring horizontal and vertical pixel pairs with mismatching triangle IDs and, as previously described in conjunction withFIGS.1C and1D, computing a blend weight to adjust pixel colors for silhouette edges that cross between centers of the detected neighboring horizontal and vertical pixel pairs. To prepare for the gradient computation during the backwards propagation, the results of the discontinuity analysis performed by the analytic antialias unit250during the forward pass may be stored to avoid repeating the computations during the backward pass.

FIG.2Cillustrates another block diagram of an example 3D model recovery system100suitable for use in implementing some embodiments of the present disclosure. The details of the backwards propagation pipeline260are shown. One or more of the stages in the backwards propagation pipeline260may be integrated into the corresponding stage of the rendering pipeline205. Stages250-B,240-B,230-B,220-B, and210-B in the backwards propagation pipeline260correspond to the analytic antialias unit250, the texture lookup240, the interpolation unit230, the rasterizer220, and the vertex transform unit210, respectively.

The stage250-B computes gradients using the stored results of the discontinuity analysis for each pixel pair that was analytically antialiased by the analytic antialias unit250in the forward pass. The antialiased image gradients for the pixels are transferred to vertex position gradients by determining how both vertex positions for the silhouette edges influence the blend weights. The loss gradients w.r.t. shaded pixels computed for the aliased image by the stage250-B are output as shaded pixel gradients to the stage240-B. The loss gradients w.r.t. vertex position are output by the stage250-B to the stage210-B to be transformed from clip space to 3D model space.

The stage240-B computes the loss gradients w.r.t. the attributes A and w.r.t. texels. Once a MIP-map level has been selected, operation of the forward and backward passes closely resemble attribute interpolation: the eight closest texels take the place of the three triangle vertices, and the three sub-texel coordinates that determine exact position within the eight-texel ensemble take the place of the barycentrics. MIP-mapped texturing differs from attribute interpolation by its multiscale nature: gradients are accumulated on various levels of the MIP-map pyramid in the backward pass. As all MIP-map levels of the MIP-map pyramid are obtained from the finest-level texture during the construction in the forward pass, the backward pass needs to finish by transposing the construction operation and flattening the gradient pyramid so that the gradient is specified densely at the finest level. Fortunately, this is implemented easily by starting at the coarsest level, recursively up-sampling the result and adding gradients from the next level precisely like collapsing a Laplacian pyramid. The stage240-B provides the texel gradients to the 3D model construction unit200. The texel gradients are used to adjust the texels for the global surface texture map of the 3D model.

The stage230-B is associated with the interpolation unit230and receives per-pixel loss gradients ∂L/∂A w.r.t. the interpolated attributes. The stage230-B provides the attribute gradients to the 3D model construction unit200. The attribute gradients may be used to adjust the texture coordinates for the global surface texture map of the 3D model. In an embodiment, the gradients w.r.t. the attribute tensor are computed by a scatter-add into the tensor, applying the simple Jacobians ∂A/∂{Ai0,i1,i2}={u, v, 1−u−v} to the per-pixel input gradients. By simple differentiation, the gradients w.r.t. the input barycentrics that are computed by the stage230-B are given by

The rasterizer backward pass receives, for each pixel, the gradient

[∂L∂{xc,yc,zc,wc}]=[∂L∂{u,v}][∂{u,v}{xc,yc,zc,wc}]Eq.(4)
w.r.t. the barycentrics output by the rasterizer and computes the gradients ∂L/∂{xc, yc, zc, wc} for each input vertex. The perspective mapping between barycentrics and clip-space positions is readily differentiated analytically, and the necessary output is computed by the stage220-B through

Equation (4) may be implemented as a dense operation over output pixels, using a scatter-add operation to accumulate the gradients from the pixels to the correct vertices based on the triangle IDs.

The stage210-B is associated with the vertex transform unit210and transforms the clip space gradients for the 3D model into 3D model space to provide 3D model gradients to the 3D model construction unit100. In an embodiment, the 3D model construction unit100represents the 3D model geometry directly using vertex positions, and the vertex positions are adjusted based on the 3D model gradients. In another embodiment, the 3D model construction unit100represents the 3D model geometry as a set of weights for a deformation network, and the weights are adjusted based on the 3D model gradients. The deformation network applies the set of weights to a base mesh to produce the 3D model that can be rendered for each camera position.

In an embodiment, the 3D model recovery system100is configured to construct a 2D model, where the 3D model defined by the initial geometry is replaced with a 2D model defined by polygonal 2D geometry in 2D model space. When a 2D model is constructed, the depth-related computations may be omitted. In an embodiment, the recovered 2D model represents a font or 2D clip-art defined by a 2D mesh or curved primitives.

At step305, an image of the 3D model defined by initial geometry is rendered, where an antialiasing operation performed by a rendering pipeline processes data associated with the geometry to antialias the image. In an embodiment, the initial geometry is defined by vertex locations or positions. In another embodiment, the initial geometry is defined by weights applied to a base mesh. The weights may be applied to the base mesh by a deformation network to produce the 3D model.

In an embodiment, the antialiasing operation is an analytic antialiasing operation that comprises determining, based on the data associated with the geometry, that a silhouette edge intersects a pair of neighboring pixels, computing a blend weight between the neighboring pixels, and adjusting colors of the neighboring pixels according to the blend weight. In an embodiment, the blend weight is computed based on an intersection point between the neighboring pixels. In an embodiment, a more complex calculation is performed to determine the blending factor, considering, e.g., the orientation, length, and location of edge endpoints. In an embodiment, determining comprises identifying the silhouette edge between first rendered geometry associated with a first identifier and second rendered geometry associated with a second identifier. In an embodiment, the antialiasing operation approximates a pixel integral based on a location of a silhouette edge within the pixel.

At step310, pixel differences are computed based on the image and a reference image. In an embodiment, the pixel differences are computed as a mean square per-pixel differences by a loss function. In an embodiment, the pixel differences are computed between high-dimensional embeddings of the images, e.g., computed using pre-trained neural networks.

At step315, the pixel differences are propagated backwards through the antialiasing operation of the rendering pipeline to compute geometry changes corresponding to reducing the pixel differences. In an embodiment, the pixel differences are used to compute per-pixel gradients of the aliased image. In an embodiment, the geometry changes comprise gradients of vertex positions. In an embodiment, propagating the pixel differences further comprises producing a surface texture corresponding to the 3D model. The surface texture represents lighting and/or material properties of the 3D model.

At step320, the initial geometry is adjusted based on the geometry changes to produce modified geometry defining the 3D model. Steps305,310,315, and320may be repeated for at least one additional reference image. In an embodiment, the reference image and the at least one additional reference image are each associated with a different camera position. In an embodiment, the image of the 3D model is rendered according to the camera position.

The primary goal of the 3D model recovery system100is to construct an accurate 3D model of an object. While the 3D model recovery system100may also render antialiased images of the object, generation of high-quality images should be considered as a secondary goal. The differentiable renderer215provides a framework for programmable shading and geometry processing, providing a high degree of user control through and the ability to render high-resolution images of scenes consisting of millions of geometric primitives. The differentiable renderer215provide custom, high-performance implementations for: rasterization, attribute interpolation, texture filtering, and antialiasing and differentiation operations for constructing an accurate 3D model.

Parallel Processing Architecture

FIG.4illustrates a parallel processing unit (PPU)400, in accordance with an embodiment. The PPU400may be used to implement the 3D model recovery system100. The PPU400may be used to implement one or more of the 3D model construction unit200, differentiable renderer215, rendering pipeline205, backwards propagation pipeline260, and image space loss unit245within the 3D model recovery system100. In an embodiment, a processor such as the PPU400may be configured to implement a neural network model. The neural network model may be implemented as software instructions executed by the processor or, in other embodiments, the processor can include a matrix of hardware elements configured to process a set of inputs (e.g., electrical signals representing values) to generate a set of outputs, which can represent activations of the neural network model. In yet other embodiments, the neural network model can be implemented as a combination of software instructions and processing performed by a matrix of hardware elements. Implementing the neural network model can include determining a set of parameters for the neural network model through, e.g., supervised or unsupervised training of the neural network model as well as, or in the alternative, performing inference using the set of parameters to process novel sets of inputs.

In an embodiment, the PPU400is a multi-threaded processor that is implemented on one or more integrated circuit devices. The PPU400is a latency hiding architecture designed to process many threads in parallel. A thread (e.g., a thread of execution) is an instantiation of a set of instructions configured to be executed by the PPU400. In an embodiment, the PPU400is a graphics processing unit (GPU) configured to implement a graphics rendering pipeline for processing three-dimensional (3D) graphics data in order to generate two-dimensional (2D) image data for display on a display device. In other embodiments, the PPU400may be utilized for performing general-purpose computations. While one exemplary parallel processor is provided herein for illustrative purposes, it should be strongly noted that such processor is set forth for illustrative purposes only, and that any processor may be employed to supplement and/or substitute for the same.

One or more PPUs400may be configured to accelerate thousands of High Performance Computing (HPC), data center, cloud computing, and machine learning applications. The PPU400may be configured to accelerate numerous deep learning systems and applications for autonomous vehicles, simulation, computational graphics such as ray or path tracing, deep learning, high-accuracy speech, image, and text recognition systems, intelligent video analytics, molecular simulations, drug discovery, disease diagnosis, weather forecasting, big data analytics, astronomy, molecular dynamics simulation, financial modeling, robotics, factory automation, real-time language translation, online search optimizations, and personalized user recommendations, and the like.

As shown inFIG.4, the PPU400includes an Input/Output (I/O) unit405, a front end unit415, a scheduler unit420, a work distribution unit425, a hub430, a crossbar (Xbar)470, one or more general processing clusters (GPCs)450, and one or more memory partition units480. The PPU400may be connected to a host processor or other PPUs400via one or more high-speed NVLink410interconnect. The PPU400may be connected to a host processor or other peripheral devices via an interconnect402. The PPU400may also be connected to a local memory404comprising a number of memory devices. In an embodiment, the local memory may comprise a number of dynamic random access memory (DRAM) devices. The DRAM devices may be configured as a high-bandwidth memory (HBM) subsystem, with multiple DRAM dies stacked within each device.

The NVLink410interconnect enables systems to scale and include one or more PPUs400combined with one or more CPUs, supports cache coherence between the PPUs400and CPUs, and CPU mastering. Data and/or commands may be transmitted by the NVLink410through the hub430to/from other units of the PPU400such as one or more copy engines, a video encoder, a video decoder, a power management unit, etc. (not explicitly shown). The NVLink410is described in more detail in conjunction withFIG.5B.

The I/O unit405is configured to transmit and receive communications (e.g., commands, data, etc.) from a host processor (not shown) over the interconnect402. The I/O unit405may communicate with the host processor directly via the interconnect402or through one or more intermediate devices such as a memory bridge. In an embodiment, the I/O unit405may communicate with one or more other processors, such as one or more the PPUs400via the interconnect402. In an embodiment, the I/O unit405implements a Peripheral Component Interconnect Express (PCIe) interface for communications over a PCIe bus and the interconnect402is a PCIe bus. In alternative embodiments, the I/O unit405may implement other types of well-known interfaces for communicating with external devices.

The I/O unit405decodes packets received via the interconnect402. In an embodiment, the packets represent commands configured to cause the PPU400to perform various operations. The I/O unit405transmits the decoded commands to various other units of the PPU400as the commands may specify. For example, some commands may be transmitted to the front end unit415. Other commands may be transmitted to the hub430or other units of the PPU400such as one or more copy engines, a video encoder, a video decoder, a power management unit, etc. (not explicitly shown). In other words, the I/O unit405is configured to route communications between and among the various logical units of the PPU400.

In an embodiment, a program executed by the host processor encodes a command stream in a buffer that provides workloads to the PPU400for processing. A workload may comprise several instructions and data to be processed by those instructions. The buffer is a region in a memory that is accessible (e.g., read/write) by both the host processor and the PPU400. For example, the I/O unit405may be configured to access the buffer in a system memory connected to the interconnect402via memory requests transmitted over the interconnect402. In an embodiment, the host processor writes the command stream to the buffer and then transmits a pointer to the start of the command stream to the PPU400. The front end unit415receives pointers to one or more command streams. The front end unit415manages the one or more streams, reading commands from the streams and forwarding commands to the various units of the PPU400.

The front end unit415is coupled to a scheduler unit420that configures the various GPCs450to process tasks defined by the one or more streams. The scheduler unit420is configured to track state information related to the various tasks managed by the scheduler unit420. The state may indicate which GPC450a task is assigned to, whether the task is active or inactive, a priority level associated with the task, and so forth. The scheduler unit420manages the execution of a plurality of tasks on the one or more GPCs450.

The scheduler unit420is coupled to a work distribution unit425that is configured to dispatch tasks for execution on the GPCs450. The work distribution unit425may track a number of scheduled tasks received from the scheduler unit420. In an embodiment, the work distribution unit425manages a pending task pool and an active task pool for each of the GPCs450. As a GPC450finishes the execution of a task, that task is evicted from the active task pool for the GPC450and one of the other tasks from the pending task pool is selected and scheduled for execution on the GPC450. If an active task has been idle on the GPC450, such as while waiting for a data dependency to be resolved, then the active task may be evicted from the GPC450and returned to the pending task pool while another task in the pending task pool is selected and scheduled for execution on the GPC450.

In an embodiment, a host processor executes a driver kernel that implements an application programming interface (API) that enables one or more applications executing on the host processor to schedule operations for execution on the PPU400. In an embodiment, multiple compute applications are simultaneously executed by the PPU400and the PPU400provides isolation, quality of service (QoS), and independent address spaces for the multiple compute applications. An application may generate instructions (e.g., API calls) that cause the driver kernel to generate one or more tasks for execution by the PPU400. The driver kernel outputs tasks to one or more streams being processed by the PPU400. Each task may comprise one or more groups of related threads, referred to herein as a warp. In an embodiment, a warp comprises 32 related threads that may be executed in parallel. Cooperating threads may refer to a plurality of threads including instructions to perform the task and that may exchange data through shared memory. The tasks may be allocated to one or more processing units within a GPC450and instructions are scheduled for execution by at least one warp.

The work distribution unit425communicates with the one or more GPCs450via XBar470. The XBar470is an interconnect network that couples many of the units of the PPU400to other units of the PPU400. For example, the XBar470may be configured to couple the work distribution unit425to a particular GPC450. Although not shown explicitly, one or more other units of the PPU400may also be connected to the XBar470via the hub430.

The tasks are managed by the scheduler unit420and dispatched to a GPC450by the work distribution unit425. The GPC450is configured to process the task and generate results. The results may be consumed by other tasks within the GPC450, routed to a different GPC450via the XBar470, or stored in the memory404. The results can be written to the memory404via the memory partition units480, which implement a memory interface for reading and writing data to/from the memory404. The results can be transmitted to another PPU400or CPU via the NVLink410. In an embodiment, the PPU400includes a number U of memory partition units480that is equal to the number of separate and distinct memory devices of the memory404coupled to the PPU400. Each GPC450may include a memory management unit to provide translation of virtual addresses into physical addresses, memory protection, and arbitration of memory requests. In an embodiment, the memory management unit provides one or more translation lookaside buffers (TLBs) for performing translation of virtual addresses into physical addresses in the memory404.

In an embodiment, the memory partition unit480includes a Raster Operations (ROP) unit, a level two (L2) cache, and a memory interface that is coupled to the memory404. The memory interface may implement 32, 64, 128, 1024-bit data buses, or the like, for high-speed data transfer. The PPU400may be connected to up to Y memory devices, such as high bandwidth memory stacks or graphics double-data-rate, version 5, synchronous dynamic random access memory, or other types of persistent storage. In an embodiment, the memory interface implements an HBM2 memory interface and Y equals half U. In an embodiment, the HBM2 memory stacks are located on the same physical package as the PPU400, providing substantial power and area savings compared with conventional GDDR5 SDRAM systems. In an embodiment, each HBM2 stack includes four memory dies and Y equals 4, with each HBM2 stack including two 128-bit channels per die for a total of 8 channels and a data bus width of 1024 bits.

In an embodiment, the memory404supports Single-Error Correcting Double-Error Detecting (SECDED) Error Correction Code (ECC) to protect data. ECC provides higher reliability for compute applications that are sensitive to data corruption. Reliability is especially important in large-scale cluster computing environments where PPUs400process very large datasets and/or run applications for extended periods.

In an embodiment, the PPU400implements a multi-level memory hierarchy. In an embodiment, the memory partition unit480supports a unified memory to provide a single unified virtual address space for CPU and PPU400memory, enabling data sharing between virtual memory systems. In an embodiment the frequency of accesses by a PPU400to memory located on other processors is traced to ensure that memory pages are moved to the physical memory of the PPU400that is accessing the pages more frequently. In an embodiment, the NVLink410supports address translation services allowing the PPU400to directly access a CPU's page tables and providing full access to CPU memory by the PPU400.

In an embodiment, copy engines transfer data between multiple PPUs400or between PPUs400and CPUs. The copy engines can generate page faults for addresses that are not mapped into the page tables. The memory partition unit480can then service the page faults, mapping the addresses into the page table, after which the copy engine can perform the transfer. In a conventional system, memory is pinned (e.g., non-pageable) for multiple copy engine operations between multiple processors, substantially reducing the available memory. With hardware page faulting, addresses can be passed to the copy engines without worrying if the memory pages are resident, and the copy process is transparent.

Data from the memory404or other system memory may be fetched by the memory partition unit480and stored in the L2 cache460, which is located on-chip and is shared between the various GPCs450. As shown, each memory partition unit480includes a portion of the L2 cache associated with a corresponding memory404. Lower level caches may then be implemented in various units within the GPCs450. For example, each of the processing units within a GPC450may implement a level one (L1) cache. The L1 cache is private memory that is dedicated to a particular processing unit. The L2 cache460is coupled to the memory interface470and the XBar470and data from the L2 cache may be fetched and stored in each of the L1 caches for processing.

In an embodiment, the processing units within each GPC450implement a SIMD (Single-Instruction, Multiple-Data) architecture where each thread in a group of threads (e.g., a warp) is configured to process a different set of data based on the same set of instructions. All threads in the group of threads execute the same instructions. In another embodiment, the processing unit implements a SIMT (Single-Instruction, Multiple Thread) architecture where each thread in a group of threads is configured to process a different set of data based on the same set of instructions, but where individual threads in the group of threads are allowed to diverge during execution. In an embodiment, a program counter, call stack, and execution state is maintained for each warp, enabling concurrency between warps and serial execution within warps when threads within the warp diverge. In another embodiment, a program counter, call stack, and execution state is maintained for each individual thread, enabling equal concurrency between all threads, within and between warps. When execution state is maintained for each individual thread, threads executing the same instructions may be converged and executed in parallel for maximum efficiency.

Each processing unit includes a large number (e.g., 128, etc.) of distinct processing cores (e.g., functional units) that may be fully-pipelined, single-precision, double-precision, and/or mixed precision and include a floating point arithmetic logic unit and an integer arithmetic logic unit. In an embodiment, the floating point arithmetic logic units implement the IEEE 754-2008 standard for floating point arithmetic. In an embodiment, the cores include 64 single-precision (32-bit) floating point cores, 64 integer cores, 32 double-precision (64-bit) floating point cores, and 8 tensor cores.

Tensor cores configured to perform matrix operations. In particular, the tensor cores are configured to perform deep learning matrix arithmetic, such as GEMM (matrix-matrix multiplication) for convolution operations during neural network training and inferencing. In an embodiment, each tensor core operates on a 4×4 matrix and performs a matrix multiply and accumulate operation D=A×B+C, where A, B, C, and D are 4×4 matrices.

In an embodiment, the matrix multiply inputs A and B may be integer, fixed-point, or floating point matrices, while the accumulation matrices C and D may be integer, fixed-point, or floating point matrices of equal or higher bitwidths. In an embodiment, tensor cores operate on one, four, or eight bit integer input data with 32-bit integer accumulation. The 8-bit integer matrix multiply requires 1024 operations and results in a full precision product that is then accumulated using 32-bit integer addition with the other intermediate products for a 8×8×16 matrix multiply. In an embodiment, tensor Cores operate on 16-bit floating point input data with 32-bit floating point accumulation. The 16-bit floating point multiply requires 64 operations and results in a full precision product that is then accumulated using 32-bit floating point addition with the other intermediate products for a 4×4×4 matrix multiply. In practice, Tensor Cores are used to perform much larger two-dimensional or higher dimensional matrix operations, built up from these smaller elements. An API, such as CUDA 9 C++ API, exposes specialized matrix load, matrix multiply and accumulate, and matrix store operations to efficiently use Tensor Cores from a CUDA-C++ program. At the CUDA level, the warp-level interface assumes 16×16 size matrices spanning all 32 threads of the warp.

Each processing unit may also comprise M special function units (SFUs) that perform special functions (e.g., attribute evaluation, reciprocal square root, and the like). In an embodiment, the SFUs may include a tree traversal unit configured to traverse a hierarchical tree data structure. In an embodiment, the SFUs may include texture unit configured to perform texture map filtering operations. In an embodiment, the texture units are configured to load texture maps (e.g., a 2D array of texels) from the memory404and sample the texture maps to produce sampled texture values for use in shader programs executed by the processing unit. In an embodiment, the texture maps are stored in shared memory that may comprise or include an L1 cache. The texture units implement texture operations such as filtering operations using mip-maps (e.g., texture maps of varying levels of detail). In an embodiment, each processing unit includes two texture units.

Each processing unit also comprises N load store units (LSUs) that implement load and store operations between the shared memory and the register file. Each processing unit includes an interconnect network that connects each of the cores to the register file and the LSU to the register file, shared memory. In an embodiment, the interconnect network is a crossbar that can be configured to connect any of the cores to any of the registers in the register file and connect the LSUs to the register file and memory locations in shared memory.

The shared memory is an array of on-chip memory that allows for data storage and communication between the processing units and between threads within a processing unit. In an embodiment, the shared memory comprises 128 KB of storage capacity and is in the path from each of the processing units to the memory partition unit480. The shared memory can be used to cache reads and writes. One or more of the shared memory, L1 cache, L2 cache, and memory404are backing stores.

Combining data cache and shared memory functionality into a single memory block provides the best overall performance for both types of memory accesses. The capacity is usable as a cache by programs that do not use shared memory. For example, if shared memory is configured to use half of the capacity, texture and load/store operations can use the remaining capacity. Integration within the shared memory enables the shared memory to function as a high-throughput conduit for streaming data while simultaneously providing high-bandwidth and low-latency access to frequently reused data.

When configured for general purpose parallel computation, a simpler configuration can be used compared with graphics processing. Specifically, fixed function graphics processing units, are bypassed, creating a much simpler programming model. In the general purpose parallel computation configuration, the work distribution unit425assigns and distributes blocks of threads directly to the processing units within the GPCs450. Threads execute the same program, using a unique thread ID in the calculation to ensure each thread generates unique results, using the processing unit(s) to execute the program and perform calculations, shared memory to communicate between threads, and the LSU to read and write global memory through the shared memory and the memory partition unit480. When configured for general purpose parallel computation, the processing units can also write commands that the scheduler unit420can use to launch new work on the processing units.

The PPU400may be included in a desktop computer, a laptop computer, a tablet computer, servers, supercomputers, a smart-phone (e.g., a wireless, hand-held device), personal digital assistant (PDA), a digital camera, a vehicle, a head mounted display, a hand-held electronic device, and the like. In an embodiment, the PPU400is embodied on a single semiconductor substrate. In another embodiment, the PPU400is included in a system-on-a-chip (SoC) along with one or more other devices such as additional PPUs400, the memory404, a reduced instruction set computer (RISC) CPU, a memory management unit (MMU), a digital-to-analog converter (DAC), and the like.

In an embodiment, the PPU400may be included on a graphics card that includes one or more memory devices. The graphics card may be configured to interface with a PCIe slot on a motherboard of a desktop computer. In yet another embodiment, the PPU400may be an integrated graphics processing unit (iGPU) or parallel processor included in the chipset of the motherboard. In yet another embodiment, the PPU400may be realized in reconfigurable hardware. In yet another embodiment, parts of the PPU400may be realized in reconfigurable hardware.

Exemplary Computing System

FIG.5Ais a conceptual diagram of a processing system500implemented using the PPU400ofFIG.4, in accordance with an embodiment. The exemplary system565may be configured to implement the 3D model recovery system100and/or the method300shown inFIG.3. The processing system500includes a CPU530, switch510, and multiple PPUs400, and respective memories404.

The NVLink410provides high-speed communication links between each of the PPUs400. Although a particular number of NVLink410and interconnect402connections are illustrated inFIG.5B, the number of connections to each PPU400and the CPU530may vary. The switch510interfaces between the interconnect402and the CPU530. The PPUs400, memories404, and NVLinks410may be situated on a single semiconductor platform to form a parallel processing module525. In an embodiment, the switch510supports two or more protocols to interface between various different connections and/or links.

In another embodiment (not shown), the NVLink410provides one or more high-speed communication links between each of the PPUs400and the CPU530and the switch510interfaces between the interconnect402and each of the PPUs400. The PPUs400, memories404, and interconnect402may be situated on a single semiconductor platform to form a parallel processing module525. In yet another embodiment (not shown), the interconnect402provides one or more communication links between each of the PPUs400and the CPU530and the switch510interfaces between each of the PPUs400using the NVLink410to provide one or more high-speed communication links between the PPUs400. In another embodiment (not shown), the NVLink410provides one or more high-speed communication links between the PPUs400and the CPU530through the switch510. In yet another embodiment (not shown), the interconnect402provides one or more communication links between each of the PPUs400directly. One or more of the NVLink410high-speed communication links may be implemented as a physical NVLink interconnect or either an on-chip or on-die interconnect using the same protocol as the NVLink410.

In an embodiment, the signaling rate of each NVLink410is 20 to 25 Gigabits/second and each PPU400includes six NVLink410interfaces (as shown inFIG.5A, five NVLink410interfaces are included for each PPU400). Each NVLink410provides a data transfer rate of 25 Gigabytes/second in each direction, with six links providing 400 Gigabytes/second. The NVLinks410can be used exclusively for PPU-to-PPU communication as shown inFIG.5A, or some combination of PPU-to-PPU and PPU-to-CPU, when the CPU530also includes one or more NVLink410interfaces.

In an embodiment, the NVLink410allows direct load/store/atomic access from the CPU530to each PPU's400memory404. In an embodiment, the NVLink410supports coherency operations, allowing data read from the memories404to be stored in the cache hierarchy of the CPU530, reducing cache access latency for the CPU530. In an embodiment, the NVLink410includes support for Address Translation Services (ATS), allowing the PPU400to directly access page tables within the CPU530. One or more of the NVLinks410may also be configured to operate in a low-power mode.

FIG.5Billustrates an exemplary system565in which the various architecture and/or functionality of the various previous embodiments may be implemented. The exemplary system565may be configured to implement the 3D model recovery system100and/or the method300shown inFIG.3.

As shown, a system565is provided including at least one central processing unit530that is connected to a communication bus575. The communication bus575may directly or indirectly couple one or more of the following devices: main memory540, network interface535, CPU(s)530, display device(s)545, input device(s)560, switch510, and parallel processing system525. The communication bus575may be implemented using any suitable protocol and may represent one or more links or busses, such as an address bus, a data bus, a control bus, or a combination thereof. The communication bus575may include one or more bus or link types, such as an industry standard architecture (ISA) bus, an extended industry standard architecture (EISA) bus, a video electronics standards association (VESA) bus, a peripheral component interconnect (PCI) bus, a peripheral component interconnect express (PCIe) bus, HyperTransport, and/or another type of bus or link. In some embodiments, there are direct connections between components. As an example, the CPU(s)530may be directly connected to the main memory540. Further, the CPU(s)530may be directly connected to the parallel processing system525. Where there is direct, or point-to-point connection between components, the communication bus575may include a PCIe link to carry out the connection. In these examples, a PCI bus need not be included in the system565.

Although the various blocks ofFIG.5Care shown as connected via the communication bus575with lines, this is not intended to be limiting and is for clarity only. For example, in some embodiments, a presentation component, such as display device(s)545, may be considered an I/O component, such as input device(s)560(e.g., if the display is a touch screen). As another example, the CPU(s)530and/or parallel processing system525may include memory (e.g., the main memory540may be representative of a storage device in addition to the parallel processing system525, the CPUs530, and/or other components). In other words, the computing device ofFIG.5Cis merely illustrative. Distinction is not made between such categories as “workstation,” “server,” “laptop,” “desktop,” “tablet,” “client device,” “mobile device,” “hand-held device,” “game console,” “electronic control unit (ECU),” “virtual reality system,” and/or other device or system types, as all are contemplated within the scope of the computing device ofFIG.5C.

The system565also includes a main memory540. Control logic (software) and data are stored in the main memory540which may take the form of a variety of computer-readable media. The computer-readable media may be any available media that may be accessed by the system565. The computer-readable media may include both volatile and nonvolatile media, and removable and non-removable media. By way of example, and not limitation, the computer-readable media may comprise computer-storage media and communication media.

Computer programs, when executed, enable the system565to perform various functions. The CPU(s)530may be configured to execute at least some of the computer-readable instructions to control one or more components of the system565to perform one or more of the methods and/or processes described herein. The CPU(s)530may each include one or more cores (e.g., one, two, four, eight, twenty-eight, seventy-two, etc.) that are capable of handling a multitude of software threads simultaneously. The CPU(s)530may include any type of processor, and may include different types of processors depending on the type of system565implemented (e.g., processors with fewer cores for mobile devices and processors with more cores for servers). For example, depending on the type of system565, the processor may be an Advanced RISC Machines (ARM) processor implemented using Reduced Instruction Set Computing (RISC) or an x86 processor implemented using Complex Instruction Set Computing (CISC). The system565may include one or more CPUs530in addition to one or more microprocessors or supplementary co-processors, such as math co-processors.

In addition to or alternatively from the CPU(s)530, the parallel processing module525may be configured to execute at least some of the computer-readable instructions to control one or more components of the system565to perform one or more of the methods and/or processes described herein. The parallel processing module525may be used by the system565to render graphics (e.g., 3D graphics) or perform general purpose computations. For example, the parallel processing module525may be used for General-Purpose computing on GPUs (GPGPU). In embodiments, the CPU(s)530and/or the parallel processing module525may discretely or jointly perform any combination of the methods, processes and/or portions thereof.

The system565also includes input device(s)560, the parallel processing system525, and display device(s)545. The display device(s)545may include a display (e.g., a monitor, a touch screen, a television screen, a heads-up-display (HUD), other display types, or a combination thereof), speakers, and/or other presentation components. The display device(s)545may receive data from other components (e.g., the parallel processing system525, the CPU(s)530, etc.), and output the data (e.g., as an image, video, sound, etc.).

The network interface535may enable the system565to be logically coupled to other devices including the input devices560, the display device(s)545, and/or other components, some of which may be built in to (e.g., integrated in) the system565. Illustrative input devices560include a microphone, mouse, keyboard, joystick, game pad, game controller, satellite dish, scanner, printer, wireless device, etc. The input devices560may provide a natural user interface (NUI) that processes air gestures, voice, or other physiological inputs generated by a user. In some instances, inputs may be transmitted to an appropriate network element for further processing. An NUI may implement any combination of speech recognition, stylus recognition, facial recognition, biometric recognition, gesture recognition both on screen and adjacent to the screen, air gestures, head and eye tracking, and touch recognition (as described in more detail below) associated with a display of the system565. The system565may be include depth cameras, such as stereoscopic camera systems, infrared camera systems, RGB camera systems, touchscreen technology, and combinations of these, for gesture detection and recognition. Additionally, the system565may include accelerometers or gyroscopes (e.g., as part of an inertia measurement unit (IMU)) that enable detection of motion. In some examples, the output of the accelerometers or gyroscopes may be used by the system565to render immersive augmented reality or virtual reality.

Further, the system565may be coupled to a network (e.g., a telecommunications network, local area network (LAN), wireless network, wide area network (WAN) such as the Internet, peer-to-peer network, cable network, or the like) through a network interface535for communication purposes. The system565may be included within a distributed network and/or cloud computing environment.

The network interface535may include one or more receivers, transmitters, and/or transceivers that enable the system565to communicate with other computing devices via an electronic communication network, included wired and/or wireless communications. The network interface535may include components and functionality to enable communication over any of a number of different networks, such as wireless networks (e.g., Wi-Fi, Z-Wave, Bluetooth, Bluetooth LE, ZigBee, etc.), wired networks (e.g., communicating over Ethernet or InfiniBand), low-power wide-area networks (e.g., LoRaWAN, SigFox, etc.), and/or the Internet.

The system565may also include a secondary storage (not shown). The secondary storage includes, for example, a hard disk drive and/or a removable storage drive, representing a floppy disk drive, a magnetic tape drive, a compact disk drive, digital versatile disk (DVD) drive, recording device, universal serial bus (USB) flash memory. The removable storage drive reads from and/or writes to a removable storage unit in a well-known manner. The system565may also include a hard-wired power supply, a battery power supply, or a combination thereof (not shown). The power supply may provide power to the system565to enable the components of the system565to operate.

Each of the foregoing modules and/or devices may even be situated on a single semiconductor platform to form the system565. Alternately, the various modules may also be situated separately or in various combinations of semiconductor platforms per the desires of the user. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Example Network Environments

Network environments suitable for use in implementing embodiments of the disclosure may include one or more client devices, servers, network attached storage (NAS), other backend devices, and/or other device types. The client devices, servers, and/or other device types (e.g., each device) may be implemented on one or more instances of the processing system500ofFIG.5Aand/or exemplary system565ofFIG.5B—e.g., each device may include similar components, features, and/or functionality of the processing system500and/or exemplary system565.

Machine Learning

Neural networks rely heavily on matrix math operations, and complex multi-layered networks require tremendous amounts of floating-point performance and bandwidth for both efficiency and speed. With thousands of processing cores, optimized for matrix math operations, and delivering tens to hundreds of TFLOPS of performance, the PPU400is a computing platform capable of delivering performance required for deep neural network-based artificial intelligence and machine learning applications.

Furthermore, images generated applying one or more of the techniques disclosed herein may be used to train, test, or certify DNNs used to recognize objects and environments in the real world. Such images may include scenes of roadways, factories, buildings, urban settings, rural settings, humans, animals, and any other physical object or real-world setting. Such images may be used to train, test, or certify DNNs that are employed in machines or robots to manipulate, handle, or modify physical objects in the real world. Furthermore, such images may be used to train, test, or certify DNNs that are employed in autonomous vehicles to navigate and move the vehicles through the real world. Additionally, images generated applying one or more of the techniques disclosed herein may be used to convey information to users of such machines, robots, and vehicles.

FIG.5Cillustrates components of an exemplary system555that can be used to train and utilize machine learning, in accordance with at least one embodiment. As will be discussed, various components can be provided by various combinations of computing devices and resources, or a single computing system, which may be under control of a single entity or multiple entities. Further, aspects may be triggered, initiated, or requested by different entities. In at least one embodiment training of a neural network might be instructed by a provider associated with provider environment506, while in at least one embodiment training might be requested by a customer or other user having access to a provider environment through a client device502or other such resource. In at least one embodiment, training data (or data to be analyzed by a trained neural network) can be provided by a provider, a user, or a third party content provider524. In at least one embodiment, client device502may be a vehicle or object that is to be navigated on behalf of a user, for example, which can submit requests and/or receive instructions that assist in navigation of a device.

In at least one embodiment, requests are able to be submitted across at least one network504to be received by a provider environment506. In at least one embodiment, a client device may be any appropriate electronic and/or computing devices enabling a user to generate and send such requests, such as, but not limited to, desktop computers, notebook computers, computer servers, smartphones, tablet computers, gaming consoles (portable or otherwise), computer processors, computing logic, and set-top boxes. Network(s)504can include any appropriate network for transmitting a request or other such data, as may include Internet, an intranet, an Ethernet, a cellular network, a local area network (LAN), a wide area network (WAN), a personal area network (PAN), an ad hoc network of direct wireless connections among peers, and so on.

In at least one embodiment, requests can be received at an interface layer508, which can forward data to a training and inference manager532, in this example. The training and inference manager532can be a system or service including hardware and software for managing requests and service corresponding data or content, in at least one embodiment, the training and inference manager532can receive a request to train a neural network, and can provide data for a request to a training module512. In at least one embodiment, training module512can select an appropriate model or neural network to be used, if not specified by the request, and can train a model using relevant training data. In at least one embodiment, training data can be a batch of data stored in a training data repository514, received from client device502, or obtained from a third party provider524. In at least one embodiment, training module512can be responsible for training data. A neural network can be any appropriate network, such as a recurrent neural network (RNN) or convolutional neural network (CNN). Once a neural network is trained and successfully evaluated, a trained neural network can be stored in a model repository516, for example, that may store different models or networks for users, applications, or services, etc. In at least one embodiment, there may be multiple models for a single application or entity, as may be utilized based on a number of different factors.

In at least one embodiment, at a subsequent point in time, a request may be received from client device502(or another such device) for content (e.g., path determinations) or data that is at least partially determined or impacted by a trained neural network. This request can include, for example, input data to be processed using a neural network to obtain one or more inferences or other output values, classifications, or predictions, or for at least one embodiment, input data can be received by interface layer508and directed to inference module518, although a different system or service can be used as well. In at least one embodiment, inference module518can obtain an appropriate trained network, such as a trained deep neural network (DNN) as discussed herein, from model repository516if not already stored locally to inference module518. Inference module518can provide data as input to a trained network, which can then generate one or more inferences as output. This may include, for example, a classification of an instance of input data. In at least one embodiment, inferences can then be transmitted to client device502for display or other communication to a user. In at least one embodiment, context data for a user may also be stored to a user context data repository522, which may include data about a user which may be useful as input to a network in generating inferences, or determining data to return to a user after obtaining instances. In at least one embodiment, relevant data, which may include at least some of input or inference data, may also be stored to a local database534for processing future requests. In at least one embodiment, a user can use account information or other information to access resources or functionality of a provider environment. In at least one embodiment, if permitted and available, user data may also be collected and used to further train models, in order to provide more accurate inferences for future requests. In at least one embodiment, requests may be received through a user interface to a machine learning application526executing on client device502, and results displayed through a same interface. A client device can include resources such as a processor528and memory562for generating a request and processing results or a response, as well as at least one data storage element552for storing data for machine learning application526.

In at least one embodiment a processor528(or a processor of training module512or inference module518) will be a central processing unit (CPU). As mentioned, however, resources in such environments can utilize GPUs to process data for at least certain types of requests. With thousands of cores, GPUs, such as PPU300are designed to handle substantial parallel workloads and, therefore, have become popular in deep learning for training neural networks and generating predictions. While use of GPUs for offline builds has enabled faster training of larger and more complex models, generating predictions offline implies that either request-time input features cannot be used or predictions must be generated for all permutations of features and stored in a lookup table to serve real-time requests. If a deep learning framework supports a CPU-mode and a model is small and simple enough to perform a feed-forward on a CPU with a reasonable latency, then a service on a CPU instance could host a model. In this case, training can be done offline on a GPU and inference done in real-time on a CPU. If a CPU approach is not viable, then a service can run on a GPU instance. Because GPUs have different performance and cost characteristics than CPUs, however, running a service that offloads a runtime algorithm to a GPU can require it to be designed differently from a CPU based service.

In at least one embodiment, video data can be provided from client device502for enhancement in provider environment506. In at least one embodiment, video data can be processed for enhancement on client device502. In at least one embodiment, video data may be streamed from a third party content provider524and enhanced by third party content provider524, provider environment506, or client device502. In at least one embodiment, video data can be provided from client device502for use as training data in provider environment506.

In at least one embodiment, supervised and/or unsupervised training can be performed by the client device502and/or the provider environment506. In at least one embodiment, a set of training data514(e.g., classified or labeled data) is provided as input to function as training data. In at least one embodiment, training data can include instances of at least one type of object for which a neural network is to be trained, as well as information that identifies that type of object. In at least one embodiment, training data might include a set of images that each includes a representation of a type of object, where each image also includes, or is associated with, a label, metadata, classification, or other piece of information identifying a type of object represented in a respective image. Various other types of data may be used as training data as well, as may include text data, audio data, video data, and so on. In at least one embodiment, training data514is provided as training input to a training module512. In at least one embodiment, training module512can be a system or service that includes hardware and software, such as one or more computing devices executing a training application, for training a neural network (or other model or algorithm, etc.). In at least one embodiment, training module512receives an instruction or request indicating a type of model to be used for training, in at least one embodiment, a model can be any appropriate statistical model, network, or algorithm useful for such purposes, as may include an artificial neural network, deep learning algorithm, learning classifier, Bayesian network, and so on. In at least one embodiment, training module512can select an initial model, or other untrained model, from an appropriate repository516and utilize training data514to train a model, thereby generating a trained model (e.g., trained deep neural network) that can be used to classify similar types of data, or generate other such inferences. In at least one embodiment where training data is not used, an appropriate initial model can still be selected for training on input data per training module512.

In at least one embodiment, a model can be trained in a number of different ways, as may depend in part upon a type of model selected. In at least one embodiment, a machine learning algorithm can be provided with a set of training data, where a model is a model artifact created by a training process. In at least one embodiment, each instance of training data contains a correct answer (e.g., classification), which can be referred to as a target or target attribute. In at least one embodiment, a learning algorithm finds patterns in training data that map input data attributes to a target, an answer to be predicted, and a machine learning model is output that captures these patterns. In at least one embodiment, a machine learning model can then be used to obtain predictions on new data for which a target is not specified.

In at least one embodiment, training and inference manager532can select from a set of machine learning models including binary classification, multiclass classification, generative, and regression models. In at least one embodiment, a type of model to be used can depend at least in part upon a type of target to be predicted.

Graphics Processing Pipeline

In an embodiment, the PPU400comprises a graphics processing unit (GPU). The PPU400is configured to receive commands that specify shader programs for processing graphics data. Graphics data may be defined as a set of primitives such as points, lines, triangles, quads, triangle strips, and the like. Typically, a primitive includes data that specifies a number of vertices for the primitive (e.g., in a model-space coordinate system) as well as attributes associated with each vertex of the primitive. The PPU400can be configured to process the graphics primitives to generate a frame buffer (e.g., pixel data for each of the pixels of the display).

An application writes model data for a scene (e.g., a collection of vertices and attributes) to a memory such as a system memory or memory404. The model data defines each of the objects that may be visible on a display. The application then makes an API call to the driver kernel that requests the model data to be rendered and displayed. The driver kernel reads the model data and writes commands to the one or more streams to perform operations to process the model data. The commands may reference different shader programs to be implemented on the processing units within the PPU400including one or more of a vertex shader, hull shader, domain shader, geometry shader, and a pixel shader. For example, one or more of the processing units may be configured to execute a vertex shader program that processes a number of vertices defined by the model data. In an embodiment, the different processing units may be configured to execute different shader programs concurrently. For example, a first subset of processing units may be configured to execute a vertex shader program while a second subset of processing units may be configured to execute a pixel shader program. The first subset of processing units processes vertex data to produce processed vertex data and writes the processed vertex data to the L2 cache460and/or the memory404. After the processed vertex data is rasterized (e.g., transformed from three-dimensional data into two-dimensional data in screen space) to produce fragment data, the second subset of processing units executes a pixel shader to produce processed fragment data, which is then blended with other processed fragment data and written to the frame buffer in memory404. The vertex shader program and pixel shader program may execute concurrently, processing different data from the same scene in a pipelined fashion until all of the model data for the scene has been rendered to the frame buffer. Then, the contents of the frame buffer are transmitted to a display controller for display on a display device.

FIG.6Ais a conceptual diagram of a graphics processing pipeline600implemented by the PPU400ofFIG.4, in accordance with an embodiment. The graphics processing pipeline600is an abstract flow diagram of the processing steps implemented to generate 2D computer-generated images from 3D geometry data. As is well-known, pipeline architectures may perform long latency operations more efficiently by splitting up the operation into a plurality of stages, where the output of each stage is coupled to the input of the next successive stage. Thus, the graphics processing pipeline600receives input data601that is transmitted from one stage to the next stage of the graphics processing pipeline600to generate output data602. In an embodiment, the graphics processing pipeline600may represent a graphics processing pipeline defined by the OpenGL® API. As an option, the graphics processing pipeline600may be implemented in the context of the functionality and architecture of the previous Figures and/or any subsequent Figure(s).

As shown inFIG.6A, the graphics processing pipeline600comprises a pipeline architecture that includes a number of stages. The stages include, but are not limited to, a data assembly stage610, a vertex shading stage620, a primitive assembly stage630, a geometry shading stage640, a viewport scale, cull, and clip (VSCC) stage650, a rasterization stage660, a fragment shading stage670, and a raster operations stage680. In an embodiment, the input data601comprises commands that configure the processing units to implement the stages of the graphics processing pipeline600and geometric primitives (e.g., points, lines, triangles, quads, triangle strips or fans, etc.) to be processed by the stages. The output data602may comprise pixel data (e.g., color data) that is copied into a frame buffer or other type of surface data structure in a memory.

The data assembly stage610receives the input data601that specifies vertex data for high-order surfaces, primitives, or the like. The data assembly stage610collects the vertex data in a temporary storage or queue, such as by receiving a command from the host processor that includes a pointer to a buffer in memory and reading the vertex data from the buffer. The vertex data is then transmitted to the vertex shading stage620for processing.

The vertex shading stage620processes vertex data by performing a set of operations (e.g., a vertex shader or a program) once for each of the vertices. Vertices may be, e.g., specified as a 4-coordinate vector (e.g., <x, y, z, w>) associated with one or more vertex attributes (e.g., color, texture coordinates, surface normal, etc.). The vertex shading stage620may manipulate individual vertex attributes such as position, color, texture coordinates, and the like. In other words, the vertex shading stage620performs operations on the vertex coordinates or other vertex attributes associated with a vertex. Such operations commonly including lighting operations (e.g., modifying color attributes for a vertex) and transformation operations (e.g., modifying the coordinate space for a vertex). For example, vertices may be specified using coordinates in an object-coordinate space, which are transformed by multiplying the coordinates by a matrix that translates the coordinates from the object-coordinate space into a world space or a normalized-device-coordinate (NCD) space. The vertex shading stage620generates transformed vertex data that is transmitted to the primitive assembly stage630.

The primitive assembly stage630collects vertices output by the vertex shading stage620and groups the vertices into geometric primitives for processing by the geometry shading stage640. For example, the primitive assembly stage630may be configured to group every three consecutive vertices as a geometric primitive (e.g., a triangle) for transmission to the geometry shading stage640. In some embodiments, specific vertices may be reused for consecutive geometric primitives (e.g., two consecutive triangles in a triangle strip may share two vertices). The primitive assembly stage630transmits geometric primitives (e.g., a collection of associated vertices) to the geometry shading stage640.

The geometry shading stage640processes geometric primitives by performing a set of operations (e.g., a geometry shader or program) on the geometric primitives. Tessellation operations may generate one or more geometric primitives from each geometric primitive. In other words, the geometry shading stage640may subdivide each geometric primitive into a finer mesh of two or more geometric primitives for processing by the rest of the graphics processing pipeline600. The geometry shading stage640transmits geometric primitives to the viewport SCC stage650.

In an embodiment, the graphics processing pipeline600may operate within a streaming multiprocessor and the vertex shading stage620, the primitive assembly stage630, the geometry shading stage640, the fragment shading stage670, and/or hardware/software associated therewith, may sequentially perform processing operations. Once the sequential processing operations are complete, in an embodiment, the viewport SCC stage650may utilize the data. In an embodiment, primitive data processed by one or more of the stages in the graphics processing pipeline600may be written to a cache (e.g. L1 cache, a vertex cache, etc.). In this case, in an embodiment, the viewport SCC stage650may access the data in the cache. In an embodiment, the viewport SCC stage650and the rasterization stage660are implemented as fixed function circuitry.

The viewport SCC stage650performs viewport scaling, culling, and clipping of the geometric primitives. Each surface being rendered to is associated with an abstract camera position. The camera position represents a location of a viewer looking at the scene and defines a viewing frustum that encloses the objects of the scene. The viewing frustum may include a viewing plane, a rear plane, and four clipping planes. Any geometric primitive entirely outside of the viewing frustum may be culled (e.g., discarded) because the geometric primitive will not contribute to the final rendered scene. Any geometric primitive that is partially inside the viewing frustum and partially outside the viewing frustum may be clipped (e.g., transformed into a new geometric primitive that is enclosed within the viewing frustum. Furthermore, geometric primitives may each be scaled based on a depth of the viewing frustum. All potentially visible geometric primitives are then transmitted to the rasterization stage660.

The rasterization stage660converts the 3D geometric primitives into 2D fragments (e.g. capable of being utilized for display, etc.). The rasterization stage660may be configured to utilize the vertices of the geometric primitives to setup a set of plane equations from which various attributes can be interpolated. The rasterization stage660may also compute a coverage mask for a plurality of pixels that indicates whether one or more sample locations for the pixel intercept the geometric primitive. In an embodiment, z-testing may also be performed to determine if the geometric primitive is occluded by other geometric primitives that have already been rasterized. The rasterization stage660generates fragment data (e.g., interpolated vertex attributes associated with a particular sample location for each covered pixel) that are transmitted to the fragment shading stage670.

The fragment shading stage670processes fragment data by performing a set of operations (e.g., a fragment shader or a program) on each of the fragments. The fragment shading stage670may generate pixel data (e.g., color values) for the fragment such as by performing lighting operations or sampling texture maps using interpolated texture coordinates for the fragment. The fragment shading stage670generates pixel data that is transmitted to the raster operations stage680.

The raster operations stage680may perform various operations on the pixel data such as performing alpha tests, stencil tests, and blending the pixel data with other pixel data corresponding to other fragments associated with the pixel. When the raster operations stage680has finished processing the pixel data (e.g., the output data602), the pixel data may be written to a render target such as a frame buffer, a color buffer, or the like.

It will be appreciated that one or more additional stages may be included in the graphics processing pipeline600in addition to or in lieu of one or more of the stages described above. Various implementations of the abstract graphics processing pipeline may implement different stages. Furthermore, one or more of the stages described above may be excluded from the graphics processing pipeline in some embodiments (such as the geometry shading stage640). Other types of graphics processing pipelines are contemplated as being within the scope of the present disclosure. Furthermore, any of the stages of the graphics processing pipeline600may be implemented by one or more dedicated hardware units within a graphics processor such as PPU400. Other stages of the graphics processing pipeline600may be implemented by programmable hardware units such as the processing unit within the PPU400.

The graphics processing pipeline600may be implemented via an application executed by a host processor, such as a CPU. In an embodiment, a device driver may implement an application programming interface (API) that defines various functions that can be utilized by an application in order to generate graphical data for display. The device driver is a software program that includes a plurality of instructions that control the operation of the PPU400. The API provides an abstraction for a programmer that lets a programmer utilize specialized graphics hardware, such as the PPU400, to generate the graphical data without requiring the programmer to utilize the specific instruction set for the PPU400. The application may include an API call that is routed to the device driver for the PPU400. The device driver interprets the API call and performs various operations to respond to the API call. In some instances, the device driver may perform operations by executing instructions on the CPU. In other instances, the device driver may perform operations, at least in part, by launching operations on the PPU400utilizing an input/output interface between the CPU and the PPU400. In an embodiment, the device driver is configured to implement the graphics processing pipeline600utilizing the hardware of the PPU400.

Various programs may be executed within the PPU400in order to implement the various stages of the graphics processing pipeline600. For example, the device driver may launch a kernel on the PPU400to perform the vertex shading stage620on one processing unit (or multiple processing units). The device driver (or the initial kernel executed by the PPU400) may also launch other kernels on the PPU400to perform other stages of the graphics processing pipeline600, such as the geometry shading stage640and the fragment shading stage670. In addition, some of the stages of the graphics processing pipeline600may be implemented on fixed unit hardware such as a rasterizer or a data assembler implemented within the PPU400. It will be appreciated that results from one kernel may be processed by one or more intervening fixed function hardware units before being processed by a subsequent kernel on a processing unit.

Images generated applying one or more of the techniques disclosed herein may be displayed on a monitor or other display device. In some embodiments, the display device may be coupled directly to the system or processor generating or rendering the images. In other embodiments, the display device may be coupled indirectly to the system or processor such as via a network. Examples of such networks include the Internet, mobile telecommunications networks, a WIFI network, as well as any other wired and/or wireless networking system. When the display device is indirectly coupled, the images generated by the system or processor may be streamed over the network to the display device. Such streaming allows, for example, video games or other applications, which render images, to be executed on a server, a data center, or in a cloud-based computing environment and the rendered images to be transmitted and displayed on one or more user devices (such as a computer, video game console, smartphone, other mobile device, etc.) that are physically separate from the server or data center. Hence, the techniques disclosed herein can be applied to enhance the images that are streamed and to enhance services that stream images such as NVIDIA GeForce Now (GFN), Google Stadia, and the like.

Example Game Streaming System

FIG.6Bis an example system diagram for a game streaming system605, in accordance with some embodiments of the present disclosure.FIG.6Bincludes game server(s)603(which may include similar components, features, and/or functionality to the example processing system500ofFIG.5Aand/or exemplary system565ofFIG.5B), client device(s)604(which may include similar components, features, and/or functionality to the example processing system500ofFIG.5Aand/or exemplary system565ofFIG.5B), and network(s)606(which may be similar to the network(s) described herein). In some embodiments of the present disclosure, the system605may be implemented.

In the system605, for a game session, the client device(s)604may only receive input data in response to inputs to the input device(s), transmit the input data to the game server(s)603, receive encoded display data from the game server(s)603, and display the display data on the display624. As such, the more computationally intense computing and processing is offloaded to the game server(s)603(e.g., rendering—in particular ray or path tracing—for graphical output of the game session is executed by the GPU(s) of the game server(s)603). In other words, the game session is streamed to the client device(s)604from the game server(s)603, thereby reducing the requirements of the client device(s)604for graphics processing and rendering.

For example, with respect to an instantiation of a game session, a client device604may be displaying a frame of the game session on the display624based on receiving the display data from the game server(s)603. The client device604may receive an input to one of the input device(s) and generate input data in response. The client device604may transmit the input data to the game server(s)603via the communication interface621and over the network(s)606(e.g., the Internet), and the game server(s)603may receive the input data via the communication interface618. The CPU(s) may receive the input data, process the input data, and transmit data to the GPU(s) that causes the GPU(s) to generate a rendering of the game session. For example, the input data may be representative of a movement of a character of the user in a game, firing a weapon, reloading, passing a ball, turning a vehicle, etc. The rendering component612may render the game session (e.g., representative of the result of the input data) and the render capture component614may capture the rendering of the game session as display data (e.g., as image data capturing the rendered frame of the game session). The rendering of the game session may include ray or path-traced lighting and/or shadow effects, computed using one or more parallel processing units—such as GPUs, which may further employ the use of one or more dedicated hardware accelerators or processing cores to perform ray or path-tracing techniques—of the game server(s)603. The encoder616may then encode the display data to generate encoded display data and the encoded display data may be transmitted to the client device604over the network(s)606via the communication interface618. The client device604may receive the encoded display data via the communication interface621and the decoder622may decode the encoded display data to generate the display data. The client device604may then display the display data via the display624.

It is noted that the techniques described herein may be embodied in executable instructions stored in a computer readable medium for use by or in connection with a processor-based instruction execution machine, system, apparatus, or device. It will be appreciated by those skilled in the art that, for some embodiments, various types of computer-readable media can be included for storing data. As used herein, a “computer-readable medium” includes one or more of any suitable media for storing the executable instructions of a computer program such that the instruction execution machine, system, apparatus, or device may read (or fetch) the instructions from the computer-readable medium and execute the instructions for carrying out the described embodiments. Suitable storage formats include one or more of an electronic, magnetic, optical, and electromagnetic format. A non-exhaustive list of conventional exemplary computer-readable medium includes: a portable computer diskette; a random-access memory (RAM); a read-only memory (ROM); an erasable programmable read only memory (EPROM); a flash memory device; and optical storage devices, including a portable compact disc (CD), a portable digital video disc (DVD), and the like.

It should be understood that the arrangement of components illustrated in the attached Figures are for illustrative purposes and that other arrangements are possible. For example, one or more of the elements described herein may be realized, in whole or in part, as an electronic hardware component. Other elements may be implemented in software, hardware, or a combination of software and hardware. Moreover, some or all of these other elements may be combined, some may be omitted altogether, and additional components may be added while still achieving the functionality described herein. Thus, the subject matter described herein may be embodied in many different variations, and all such variations are contemplated to be within the scope of the claims.

To facilitate an understanding of the subject matter described herein, many aspects are described in terms of sequences of actions. It will be recognized by those skilled in the art that the various actions may be performed by specialized circuits or circuitry, by program instructions being executed by one or more processors, or by a combination of both. The description herein of any sequence of actions is not intended to imply that the specific order described for performing that sequence must be followed. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

The use of the terms “a” and “an” and “the” and similar references in the context of describing the subject matter (particularly in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the scope of protection sought is defined by the claims as set forth hereinafter together with any equivalents thereof. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illustrate the subject matter and does not pose a limitation on the scope of the subject matter unless otherwise claimed. The use of the term “based on” and other like phrases indicating a condition for bringing about a result, both in the claims and in the written description, is not intended to foreclose any other conditions that bring about that result. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention as claimed.