bluuebunny/crossref_metadata_2025 huggingface dataset:
Plastic trees
Authors: Pirk Sören , Stava Ondrej , Kratt Julian , Said Michel Abdul Massih , Neubert Boris , Měch Radomír , Benes Bedrich , Deussen Oliver
Published: August 2012

We present a dynamic tree modeling and representation technique that allows complex tree models to interact with their environment. Our method uses changes in the light distribution and proximity to solid obstacles and other trees as approximations of biologically motivated transformations on a skeletal representation of the tree's main branches and its procedurally generated foliage. Parts of the tree are transformed only when required, thus our approach is much faster than common algorithms such as Open L-Systems or space colonization methods. Input is a skeleton-based tree geometry that can be computed from common tree production systems or from reconstructed laser scanning models. Our approach enables content creators to directly interact with trees and to create visually convincing ecosystems interactively. We present different interaction types and evaluate our method by comparing our transformations to biologically based growth simulation techniques.
Stochastic tomography and its applications in 3D imaging of mixing fluids
Authors: Gregson James , Krimerman Michael , Hullin Matthias B. , Heidrich Wolfgang
Published: August 2012

We present a novel approach for highly detailed 3D imaging of turbulent fluid mixing behaviors. The method is based on visible light computed tomography, and is made possible by a new stochastic tomographic reconstruction algorithm based on random walks. We show that this new stochastic algorithm is competitive with specialized tomography solvers such as SART, but can also easily include arbitrary convex regularizers that make it possible to obtain high-quality reconstructions with a very small number of views. Finally, we demonstrate that the same stochastic tomography approach can also be used to directly re-render arbitrary 2D projections without the need to ever store a 3D volume grid.
Tracking surfaces with evolving topology
Authors: Bojsen-Hansen Morten , Li Hao , Wojtan Chris
Published: August 2012

We present a method for recovering a temporally coherent, deforming triangle mesh with arbitrarily changing topology from an incoherent sequence of static closed surfaces. We solve this problem using the surface geometry alone, without any prior information like surface templates or velocity fields. Our system combines a proven strategy for triangle mesh improvement, a robust multi-resolution non-rigid registration routine, and a reliable technique for changing surface mesh topology. We also introduce a novel topological constraint enforcement algorithm to ensure that the output and input always have similar topology. We apply our technique to a series of diverse input data from video reconstructions, physics simulations, and artistic morphs. The structured output of our algorithm allows us to efficiently track information like colors and displacement maps, recover velocity information, and solve PDEs on the mesh as a post process.
A probabilistic model for component-based shape synthesis
Authors: Kalogerakis Evangelos , Chaudhuri Siddhartha , Koller Daphne , Koltun Vladlen
Published: August 2012

We present an approach to synthesizing shapes from complex domains, by identifying new plausible combinations of components from existing shapes. Our primary contribution is a new generative model of component-based shape structure. The model represents probabilistic relationships between properties of shape components, and relates them to learned underlying causes of structural variability within the domain. These causes are treated as latent variables, leading to a compact representation that can be effectively learned without supervision from a set of compatibly segmented shapes. We evaluate the model on a number of shape datasets with complex structural variability and demonstrate its application to amplification of shape databases and to interactive shape synthesis.
Fit and diverse
Authors: Xu Kai , Zhang Hao , Cohen-Or Daniel , Chen Baoquan
Published: August 2012

We introduce
set evolution
as a means for creative 3D shape modeling, where an initial population of 3D models is evolved to produce generations of novel shapes. Part of the evolving set is presented to a user as a shape gallery to offer modeling suggestions. User preferences define the fitness for the evolution so that over time, the shape population will mainly consist of individuals with good fitness. However, to inspire the user's creativity, we must also keep the evolving set diverse. Hence the evolution is "
fit and diverse
", drawing motivation from evolution theory. We introduce a novel part crossover operator which works at the finer-level part structures of the shapes, leading to significant variations and thus increased diversity in the evolved shape structures. Diversity is also achieved by explicitly compromising the fitness scores on a portion of the evolving population. We demonstrate the effectiveness of set evolution on man-made shapes. We show that selecting only models with high fitness leads to an elite population with low diversity. By keeping the population fit and diverse, the evolution can generate inspiring, and sometimes unexpected, shapes.
Bidirectional lightcuts
Authors: Walter Bruce , Khungurn Pramook , Bala Kavita
Published: August 2012

Scenes modeling the real-world combine a wide variety of phenomena including glossy materials, detailed heterogeneous anisotropic media, subsurface scattering, and complex illumination. Predictive rendering of such scenes is difficult; unbiased algorithms are typically too slow or too noisy. Virtual point light (VPL) based algorithms produce low noise results across a wide range of performance/accuracy tradeoffs, from interactive rendering to high quality offline rendering, but their bias means that locally important illumination features may be missing.

We introduce a bidirectional formulation and a set of weighting strategies to significantly reduce the bias in VPL-based rendering algorithms. Our approach,
bidirectional lightcuts
, maintains the scalability and low noise global illumination advantages of prior VPL-based work, while significantly extending their generality to support a wider range of important materials and visual cues. We demonstrate scalable, efficient, and low noise rendering of scenes with highly complex materials including gloss, BSSRDFs, and anisotropic volumetric models.
Virtual ray lights for rendering scenes with participating media
Authors: Novák Jan , Nowrouzezahrai Derek , Dachsbacher Carsten , Jarosz Wojciech
Published: August 2012

We present an efficient many-light algorithm for simulating indirect illumination in, and from, participating media. Instead of creating discrete virtual point lights (VPLs) at vertices of random-walk paths, we present a continuous generalization that places
virtual ray lights
(VRLs) along each path segment in the medium. Furthermore, instead of evaluating the lighting independently at discrete points in the medium, we calculate the contribution of each VRL to entire camera rays through the medium using an efficient Monte Carlo product sampling technique. We prove that by spreading the energy of virtual lights along both light and camera rays, the singularities that typically plague VPL methods are significantly diminished. This greatly reduces the need to clamp energy contributions in the medium, leading to robust and
unbiased
volumetric lighting not possible with current many-light techniques. Furthermore, by acting as a form of final gather, we obtain higher-quality multiple-scattering than existing density estimation techniques like progressive photon beams.
Versatile rigid-fluid coupling for incompressible SPH
Authors: Akinci Nadir , Ihmsen Markus , Akinci Gizem , Solenthaler Barbara , Teschner Matthias
Published: August 2012

We propose a momentum-conserving two-way coupling method of SPH fluids and arbitrary rigid objects based on hydrodynamic forces. Our approach samples the surface of rigid bodies with boundary particles that interact with the fluid, preventing deficiency issues and both spatial and temporal discontinuities. The problem of inhomogeneous boundary sampling is addressed by considering the relative contribution of a boundary particle to a physical quantity. This facilitates not only the initialization process but also allows the simulation of multiple dynamic objects. Thin structures consisting of only one layer or one line of boundary particles, and also non-manifold geometries can be handled without any additional treatment. We have integrated our approach into WCSPH and PCISPH, and demonstrate its stability and flexibility with several scenarios including multiphase flow.
Video deblurring for hand-held cameras using patch-based synthesis
Authors: Cho Sunghyun , Wang Jue , Lee Seungyong
Published: August 2012

Videos captured by hand-held Cameras often contain significant camera shake, causing many frames to be blurry. Restoring shaky videos not only requires smoothing the camera motion and stabilizing the content, but also demands removing blur from video frames. However, video blur is hard to remove using existing single or multiple image deblurring techniques, as the blur kernel is both spatially and temporally varying. This paper presents a video deblurring method that can effectively restore sharp frames from blurry ones caused by camera shake. Our method is built upon the observation that due to the nature of camera shake, not all video frames are equally blurry. The same object may appear sharp on some frames while blurry on others. Our method detects sharp regions in the video, and uses them to restore blurry regions of the same content in nearby frames. Our method also ensures that the deblurred frames are both spatially and temporally coherent using patch-based synthesis. Experimental results show that our method can effectively remove complex video blur under the presence of moving objects and other outliers, which cannot be achieved using previous deconvolution-based approaches.
Videoscapes
Authors: Tompkin James , Kim Kwang In , Kautz Jan , Theobalt Christian
Published: August 2012

The abundance of mobile devices and digital cameras with video capture makes it easy to obtain large collections of video clips that contain the same location, environment, or event. However, such an unstructured collection is difficult to comprehend and explore. We propose a system that analyzes collections of unstructured but related video data to create a
Videoscape
: a data structure that enables interactive exploration of video collections by visually navigating -- spatially and/or temporally -- between different clips. We automatically identify transition opportunities, or
portals
. From these portals, we construct the Videoscape, a graph whose edges are video clips and whose nodes are portals between clips. Now structured, the videos can be interactively explored by walking the graph or by geographic map. Given this system, we gauge preference for different video transition styles in a user study, and generate heuristics that automatically choose an appropriate transition style. We evaluate our system using three further user studies, which allows us to conclude that Videoscapes provides significant benefits over related methods. Our system leads to previously unseen ways of interactive spatio-temporal exploration of casually captured videos, and we demonstrate this on several video collections.
Gabor noise by example
Authors: Galerne Bruno , Lagae Ares , Lefebvre Sylvain , Drettakis George
Published: August 2012

Procedural noise is a fundamental tool in Computer Graphics. However, designing noise patterns is hard. In this paper, we present
Gabor noise by example
, a method to estimate the parameters of bandwidth-quantized Gabor noise, a procedural noise function that can generate noise with an arbitrary power spectrum, from exemplar Gaussian textures, a class of textures that is completely characterized by their power spectrum. More specifically, we introduce (i) bandwidth-quantized Gabor noise, a generalization of Gabor noise to arbitrary power spectra that enables robust parameter estimation and efficient procedural evaluation; (ii) a robust parameter estimation technique for quantized-bandwidth Gabor noise, that automatically decomposes the noisy power spectrum estimate of an exemplar into a sparse sum of Gaussians using non-negative basis pursuit denoising; and (iii) an efficient procedural evaluation scheme for bandwidth-quantized Gabor noise, that uses multi-grid evaluation and importance sampling of the kernel parameters. Gabor noise by example preserves the traditional advantages of procedural noise, including a compact representation and a fast on-the-fly evaluation, and is mathematically well-founded.
Diffusion curve textures for resolution independent texture mapping
Authors: Sun Xin , Xie Guofu , Dong Yue , Lin Stephen , Xu Weiwei , Wang Wencheng , Tong Xin , Guo Baining
Published: August 2012

We introduce a vector representation called
diffusion curve textures
for mapping diffusion curve images (DCI) onto arbitrary surfaces. In contrast to the original
implicit
representation of DCIs [Orzan et al. 2008], where determining a single texture value requires iterative computation of the entire DCI via the Poisson equation, diffusion curve textures provide an
explicit
representation from which the texture value at any point can be solved directly, while preserving the compactness and resolution independence of diffusion curves. This is achieved through a formulation of the DCI diffusion process in terms of Green's functions. This formulation furthermore allows the texture value of any rectangular region (e.g. pixel area) to be solved in closed form, which facilitates anti-aliasing. We develop a GPU algorithm that renders anti-aliased diffusion curve textures in real time, and demonstrate the effectiveness of this method through high quality renderings with detailed control curves and color variations.
Structure-aware synthesis for predictive woven fabric appearance
Authors: Zhao Shuang , Jakob Wenzel , Marschner Steve , Bala Kavita
Published: August 2012

Woven fabrics have a wide range of appearance determined by their small-scale 3D structure. Accurately modeling this structural detail can produce highly realistic renderings of fabrics and is critical for predictive rendering of fabric appearance. But building these yarn-level volumetric models is challenging. Procedural techniques are manually intensive, and fail to capture the naturally arising irregularities which contribute significantly to the overall appearance of cloth. Techniques that acquire the detailed 3D structure of real fabric samples are constrained only to model the scanned samples and cannot represent different fabric designs.

This paper presents a new approach to creating volumetric models of woven cloth, which starts with user-specified fabric designs and produces models that correctly capture the yarn-level structural details of cloth. We create a small database of volumetric exemplars by scanning fabric samples with simple weave structures. To build an output model, our method synthesizes a new volume by copying data from the exemplars at each yarn crossing to match a weave pattern that specifies the desired output structure. Our results demonstrate that our approach generalizes well to complex designs and can produce highly realistic results at both large and small scales.
Point sampling with general noise spectrum
Authors: Zhou Yahan , Huang Haibin , Wei Li-Yi , Wang Rui
Published: August 2012

Point samples with different spectral noise properties (often defined using color names such as white, blue, green, and red) are important for many science and engineering disciplines including computer graphics. While existing techniques can easily produce white and blue noise samples, relatively little is known for generating other noise patterns. In particular, no single algorithm is available to generate different noise patterns according to user-defined spectra.

In this paper, we describe an algorithm for generating point samples that match a user-defined Fourier spectrum function. Such a spectrum function can be either obtained from a known sampling method, or completely constructed by the user. Our key idea is to convert the Fourier spectrum function into a
differential distribution function
that describes the samples' local spatial statistics; we then use a gradient descent solver to iteratively compute a sample set that matches the target differential distribution function. Our algorithm can be easily modified to achieve adaptive sampling, and we provide a GPU-based implementation. Finally, we present a variety of different sample patterns obtained using our algorithm, and demonstrate suitable applications.
Fast automatic skinning transformations
Authors: Jacobson Alec , Baran Ilya , Kavan Ladislav , Popović Jovan , Sorkine Olga
Published: August 2012

Skinning transformations are a popular way to articulate shapes and characters. However, traditional animation interfaces require all of the skinning transformations to be specified explicitly, typically using a control structure (a rig). We propose a system where the user specifies only a subset of the degrees of freedom and the rest are automatically inferred using nonlinear, rigidity energies. By utilizing a low-order model and reformulating our energy functions accordingly, our algorithm runs orders of magnitude faster than previous methods without compromising quality. In addition to the immediate boosts in performance for existing modeling and real time animation tools, our approach also opens the door to new modes of control: disconnected skeletons combined with shape-aware inverse kinematics. With automatically generated skinning weights, our method can also be used for fast variational shape modeling.
An algebraic model for parameterized shape editing
Authors: Bokeloh Martin , Wand Michael , Seidel Hans-Peter , Koltun Vladlen
Published: August 2012

We present an approach to high-level shape editing that adapts the structure of the shape while maintaining its global characteristics. Our main contribution is a new algebraic model of shape structure that characterizes shapes in terms of linked translational patterns. The space of shapes that conform to this characterization is parameterized by a small set of numerical parameters bounded by a set of linear constraints. This convex space permits a direct exploration of variations of the input shape. We use this representation to develop a robust interactive system that allows shapes to be intuitively manipulated through sparse constraints.
Edge-guided resolution enhancement in projectors via optical pixel sharing
Authors: Sajadi Behzad , Gopi M. , Majumder Aditi
Published: August 2012

Digital projection technology has improved significantly in recent years. But, the relationship of cost with respect to available resolution in projectors is still super-linear. In this paper, we present a method that uses projector light modulator panels (e.g. LCD or DMD panels) of resolution
n X n
to create a perceptually close match to a target higher resolution
cn X cn
image, where
c
is a small integer greater than 1. This is achieved by enhancing the resolution using smaller pixels at specific regions of interest like edges.

A target high resolution image (
cn X cn
) is first decomposed into (a) a high resolution (
cn X cn
) but sparse
edge image
, and (b) a complementary lower resolution (
n X n
)
non-edge image
. These images are then projected in a time sequential manner at a high frame rate to create an
edge-enhanced image
-- an image where the pixel density is not uniform but changes spatially. In 3D ready projectors with readily available refresh rate of 120Hz, such a temporal multiplexing is imperceptible to the user and the edge-enhanced image is perceptually almost identical to the target high resolution image.

To create the higher resolution edge image, we introduce the concept of
optical pixel sharing
. This reduces the projected pixel size by a factor of 1/
c
2
while increasing the pixel density by
c
2
at the edges enabling true higher resolution edges. Due to the sparsity of the edge pixels in an image we are able to choose a sufficiently large subset of these to be displayed at the higher resolution using perceptual parameters. We present a statistical analysis quantifying the expected number of pixels that will be reproduced at the higher resolution and verify it for different types of images.
Tailored displays to compensate for visual aberrations
Authors: Pamplona Vitor F. , Oliveira Manuel M. , Aliaga Daniel G. , Raskar Ramesh
Published: August 2012

We introduce tailored displays that enhance visual acuity by decomposing virtual objects and placing the resulting anisotropic pieces into the subject's focal range. The goal is to free the viewer from needing wearable optical corrections when looking at displays. Our tailoring process uses aberration and scattering maps to account for refractive errors and cataracts. It splits an object's light field into multiple instances that are each in-focus for a given eye sub-aperture. Their integration onto the retina leads to a quality improvement of perceived images when observing the display with naked eyes. The use of multiple depths to render each point of focus on the retina creates multi-focus, multi-depth displays. User evaluations and validation with modified camera optics are performed. We propose tailored displays for daily tasks where using eyeglasses are unfeasible or inconvenient (
e.g
., on head-mounted displays, e-readers, as well as for games); when a multi-focus function is required but undoable (
e.g
., driving for farsighted individuals, checking a portable device while doing physical activities); or for correcting the visual distortions produced by high-order aberrations that eyeglasses are not able to.
Panorama weaving
Authors: Summa Brian , Tierny Julien , Pascucci Valerio
Published: August 2012

A fundamental step in stitching several pictures to form a larger mosaic is the computation of boundary seams that minimize the visual artifacts in the transition between images. Current seam computation algorithms use optimization methods that may be slow, sequential, memory intensive, and prone to finding suboptimal solutions related to local minima of the chosen energy function. Moreover, even when these techniques perform well, their solution may not be perceptually ideal (or even good). Such an inflexible approach does not allow the possibility of user-based improvement. This paper introduces the
Panorama Weaving
technique for seam creation and editing in an image mosaic. First,
Panorama Weaving
provides a procedure to create boundaries for panoramas that is fast, has low memory requirements and is easy to parallelize. This technique often produces seams with lower energy than the competing global technique. Second, it provides the first interactive technique for the exploration of the seam solution space. This powerful editing capability allows the user to automatically extract energy minimizing seams given a sparse set of constraints. With a variety of empirical results, we show how
Panorama Weaving
allows the computation and editing of a wide range of digital panoramas including unstructured configurations.
Understanding and improving the realism of image composites
Authors: Xue Su , Agarwala Aseem , Dorsey Julie , Rushmeier Holly
Published: August 2012

Compositing is one of the most commonly performed operations in computer graphics. A realistic composite requires adjusting the appearance of the foreground and background so that they appear compatible; unfortunately, this task is challenging and poorly understood. We use statistical and visual perception experiments to study the realism of image composites. First, we evaluate a number of standard 2D image statistical measures, and identify those that are most significant in determining the realism of a composite. Then, we perform a human subjects experiment to determine how the changes in these key statistics influence human judgements of composite realism. Finally, we describe a data-driven algorithm that automatically adjusts these statistical measures in a foreground to make it more compatible with its background in a composite. We show a number of compositing results, and evaluate the performance of both our algorithm and previous work with a human subjects study.
Position-correcting tools for 2D digital fabrication
Authors: Rivers Alec , Moyer Ilan E. , Durand Frédo
Published: August 2012

Many kinds of digital fabrication are accomplished by precisely moving a tool along a digitally-specified path. This precise motion is typically accomplished fully automatically using a computer-controlled multi-axis stage. With that approach, one can only create objects smaller than the positioning stage, and large stages can be quite expensive. We propose a new approach to precise positioning of a tool that combines manual and automatic positioning: in our approach, the user coarsely positions a frame containing the tool in an approximation of the desired path, while the device tracks the frame's location and adjusts the position of the tool within the frame to correct the user's positioning error in real time. Because the automatic positioning need only cover the range of the human's positioning error, this frame can be small and inexpensive, and because the human has unlimited range, such a frame can be used to precisely position tools over an unlimited range.
REVEL
Authors: Bau Olivier , Poupyrev Ivan
Published: August 2012

REVEL is an augmented reality (AR) tactile technology that allows for change to the tactile feeling of real objects by augmenting them with virtual tactile textures using a device worn by the user. Unlike previous attempts to enhance AR environments with haptics, we neither physically actuate objects or use any force- or tactile-feedback devices, nor require users to wear tactile gloves or other apparatus on their hands. Instead, we employ the principle of
reverse electrovibration
where we inject a weak electrical signal anywhere on the user body creating an oscillating electrical field around the user's fingers. When sliding his or her fingers on a surface of the object, the user perceives highly distinctive tactile textures augmenting the physical object. By tracking the objects and location of the touch, we associate dynamic tactile sensations to the interaction context. REVEL is built upon our previous work on designing electrovibration-based tactile feedback for touch surfaces [Bau, et al. 2010]. In this paper we expand tactile interfaces based on electrovibration beyond touch surfaces and bring them into the real world. We demonstrate a broad range of application scenarios where our technology can be used to enhance AR interaction with dynamic and unobtrusive tactile feedback.
Render me real?
Authors: McDonnell Rachel , Breidt Martin , Bülthoff Heinrich H.
Published: August 2012

The realistic depiction of lifelike virtual humans has been the goal of many movie makers in the last decade. Recently, films such as
Tron: Legacy
and
The Curious Case of Benjamin Button
have produced highly realistic characters. In the real-time domain, there is also a need to deliver realistic virtual characters, with the increase in popularity of interactive drama video games (such as
L.A. Noire™
or
Heavy Rain™
). There have been mixed reactions from audiences to lifelike characters used in movies and games, with some saying that the increased realism highlights subtle imperfections, which can be disturbing. Some developers opt for a stylized rendering (such as cartoon-shading) to avoid a negative reaction [Thompson 2004]. In this paper, we investigate some of the consequences of choosing realistic or stylized rendering in order to provide guidelines for developers for creating appealing virtual characters. We conducted a series of psychophysical experiments to determine whether render style affects how virtual humans are perceived. Motion capture with synchronized eye-tracked data was used throughout to animate custom-made virtual model replicas of the captured actors.
Highlight microdisparity for improved gloss depiction
Authors: Templin Krzysztof , Didyk Piotr , Ritschel Tobias , Myszkowski Karol , Seidel Hans-Peter
Published: August 2012

Human stereo perception of glossy materials is substantially different from the perception of diffuse surfaces: A single point on a diffuse object appears the same for both eyes, whereas it appears different to both eyes on a specular object. As highlights are blurry reflections of light sources they have depth themselves, which is different from the depth of the reflecting surface. We call this difference in depth impression the "highlight disparity". Due to artistic motivation, for technical reasons, or because of incomplete data, highlights often have to be depicted on-surface, without any disparity. However, it has been shown that a lack of disparity decreases the perceived glossiness and authenticity of a material. To remedy this contradiction, our work introduces a technique for depiction of glossy materials, which improves over simple on-surface highlights, and avoids the problems of physical highlights. Our technique is computationally simple, can be easily integrated in an existing (GPU) shading system, and allows for local and interactive artistic control.
Binocular tone mapping
Authors: Yang Xuan , Zhang Linling , Wong Tien-Tsin , Heng Pheng-Ann
Published: August 2012

By extending from monocular displays to binocular displays, one additional image domain is introduced. Existing binocular display systems only utilize this additional image domain for stereopsis. Our human vision is not only able to fuse two displaced images, but also two images with difference in detail, contrast and luminance, up to a certain limit. This phenomenon is known as
binocular single vision
. Humans can perceive more visual content via binocular fusion than just a linear blending of two views. In this paper, we make a first attempt in computer graphics to utilize this human vision phenomenon, and propose a binocular tone mapping framework. The proposed framework generates a binocular low-dynamic range (LDR) image pair that preserves more human-perceivable visual content than a single LDR image using the additional image domain. Given a tone-mapped LDR image (left, without loss of generality), our framework optimally synthesizes its counterpart (right) in the image pair from the same source HDR image. The two LDR images are different, so that they can aggregately present
more human-perceivable visual richness
than a single arbitrary LDR image,
without triggering visual discomfort
. To achieve this goal, a novel
binocular viewing comfort predictor
(BVCP) is also proposed to prevent such visual discomfort. The design of BVCP is based on the findings in vision science. Through our user studies, we demonstrate the increase of human-perceivable visual richness and the effectiveness of the proposed BVCP in conservatively predicting the visual discomfort threshold of human observers.
An analytic model for full spectral sky-dome radiance
Authors: Hosek Lukas , Wilkie Alexander
Published: August 2012

We present a physically-based analytical model of the daytime sky. Based on the results of a first-principles brute force simulation of radiative transfer in the atmosphere, we use the same general approach of fitting basis function coefficients to radiance data as the Perez and Preetham models do. However, we make several modifications to this process, which together significantly improve the rendition of sunsets and high atmospheric turbidity setups -- known weak points of the Preetham model. Additionally, our model accounts for ground albedo, and handles each spectral component independently. The latter property makes it easily extensible to the near ultraviolet range of the spectrum, so that the daylight appearance of surfaces that include optical brighteners can be properly predicted. Due to its similar mathematical properties, the new model can be used as a drop-in replacement of the Preetham model.
Efficient geometrically exact continuous collision detection
Authors: Brochu Tyson , Edwards Essex , Bridson Robert
Published: August 2012

Continuous collision detection (CCD) between deforming triangle mesh elements in 3D is a critical tool for many applications. The standard method involving a cubic polynomial solver is vulnerable to rounding error, requiring the use of
ad hoc
tolerances, and nevertheless is particularly fragile in (near-)planar cases. Even with per-simulation tuning, it may still cause problems by missing collisions or erroneously flagging non-collisions. We present a
geometrically exact
alternative guaranteed to produce the correct Boolean result (significant collision or not) as if calculated with exact arithmetic, even in degenerate scenarios. Our critical insight is that only the parity of the number of collisions is needed for robust simulation, and this parity can be calculated with simpler non-constructive predicates. In essence we analyze the roots of the nonlinear system of equations defining CCD through careful consideration of the boundary of the parameter domain. The use of new conservative culling and interval filters allows typical simulations to run as fast as with the non-robust version, but without need for tuning or worries about failure cases even in geometrically degenerate scenarios. We demonstrate the effectiveness of geometrically exact detection with a novel adaptive cloth simulation, the first to guarantee to remain intersection-free despite frequent curvature-driven remeshing.
What makes Paris look like Paris?
Authors: Doersch Carl , Singh Saurabh , Gupta Abhinav , Sivic Josef , Efros Alexei A.
Published: August 2012

Given a large repository of geotagged imagery, we seek to automatically find visual elements, e. g. windows, balconies, and street signs, that are most distinctive for a certain geo-spatial area, for example the city of Paris. This is a tremendously difficult task as the visual features distinguishing architectural elements of different places can be very subtle. In addition, we face a hard search problem: given all possible patches in all images, which of them are both frequently occurring
and
geographically informative? To address these issues, we propose to use a discriminative clustering approach able to take into account the weak geographic supervision. We show that geographically representative image elements can be discovered automatically from Google Street View imagery in a discriminative manner. We demonstrate that these elements are visually interpretable and perceptually geo-informative. The discovered visual elements can also support a variety of
computational geography
tasks, such as mapping architectural correspondences and influences within and across cities, finding representative elements at different geo-spatial scales, and geographically-informed image retrieval.
Underwater rigid body dynamics
Authors: Weißmann Steffen , Pinkall Ulrich
Published: August 2012

We show that the motion of rigid bodies under water can be realistically simulated by replacing the usual inertia tensor and scalar mass by the so-called Kirchhoff tensor. This allows us to model fluid-body interaction without simulating the surrounding fluid at all. We explain some of the phenomena that arise and compare our results against real experiments. It turns out that many real scenarios (sinking bodies, balloons) can be matched using a single, hand-tuned scaling parameter. We describe how to integrate our method into an existing physics engine, which makes underwater rigid body dynamics run in real time.
Continuous penalty forces
Authors: Tang Min , Manocha Dinesh , Otaduy Miguel A. , Tong Ruofeng
Published: August 2012

We present a simple algorithm to compute continuous penalty forces to determine collision response between rigid and deformable models bounded by triangle meshes. Our algorithm computes a well-behaved solution in contrast to the traditional stability and robustness problems of penalty methods, induced by force discontinuities. We trace contact features along their deforming trajectories and accumulate penalty forces along the penetration time intervals between the overlapping feature pairs. Moreover, we present a closed-form expression to compute the continuous and smooth collision response. Our method has very small additional overhead compared to previous penalty methods, and can significantly improve the stability and robustness. We highlight its benefits on several benchmarks.
Object-space multiphase implicit functions
Authors: Yuan Zhan , Yu Yizhou , Wang Wenping
Published: August 2012

Implicit functions have a wide range of applications in entertainment, engineering and medical imaging. A standard two-phase implicit function only represents the interior and exterior of a single object. To facilitate solid modeling of heterogeneous objects with multiple internal regions, object-space multiphase implicit functions are much desired. Multiphase implicit functions have much potential in modeling natural organisms, heterogeneous mechanical parts and anatomical atlases. In this paper, we introduce a novel class of object-space multiphase implicit functions that are capable of accurately and compactly representing objects with multiple internal regions. Our proposed multiphase implicit functions facilitate true object-space geometric modeling of heterogeneous objects with non-manifold features. We present multiple methods to create object-space multiphase implicit functions from existing data, including meshes and segmented medical images. Our algorithms are inspired by machine learning algorithms for training multicategory max-margin classifiers. Comparisons demonstrate that our method achieves an error rate one order of magnitude smaller than alternative techniques.
Single-view hair modeling for portrait manipulation
Authors: Chai Menglei , Wang Lvdi , Weng Yanlin , Yu Yizhou , Guo Baining , Zhou Kun
Published: August 2012

Human hair is known to be very difficult to model or reconstruct. In this paper, we focus on applications related to portrait manipulation and take an application-driven approach to hair modeling. To enable an average user to achieve interesting portrait manipulation results, we develop a single-view hair modeling technique with modest user interaction to meet the unique requirements set by portrait manipulation. Our method relies on heuristics to generate a plausible high-resolution strand-based 3D hair model. This is made possible by an effective high-precision 2D strand tracing algorithm, which explicitly models uncertainty and local layering during tracing. The depth of the traced strands is solved through an optimization, which simultaneously considers depth constraints, layering constraints as well as regularization terms. Our single-view hair modeling enables a number of interesting applications that were previously challenging, including transferring the hairstyle of one subject to another in a potentially different pose, rendering the original portrait in a novel view and image-space hair editing.
Coupled 3D reconstruction of sparse facial hair and skin
Authors: Beeler Thabo , Bickel Bernd , Noris Gioacchino , Beardsley Paul , Marschner Steve , Sumner Robert W. , Gross Markus
Published: August 2012

Although facial hair plays an important role in individual expression, facial-hair reconstruction is not addressed by current face-capture systems. Our research addresses this limitation with an algorithm that treats hair and skin surface capture together in a coupled fashion so that a high-quality representation of hair fibers as well as the underlying skin surface can be reconstructed. We propose a passive, camera-based system that is robust against arbitrary motion since all data is acquired within the time period of a single exposure. Our reconstruction algorithm detects and traces hairs in the captured images and reconstructs them in 3D using a multiview stereo approach. Our coupled skin-reconstruction algorithm uses information about the detected hairs to deliver a skin surface that lies underneath all hairs irrespective of occlusions. In dense regions like eyebrows, we employ a hair-synthesis method to create hair fibers that plausibly match the image data. We demonstrate our scanning system on a number of individuals and show that it can successfully reconstruct a variety of facial-hair styles together with the underlying skin surface.
An information-based dynamic extrapolation model for networked virtual environments
Authors: Zhang Xin , Ward Tomás E. , Mcloone Séamus
Published: August 2012

Various Information Management techniques have been developed to help maintain a consistent shared virtual world in a Networked Virtual Environment. However, such techniques have to be carefully adapted to the application state dynamics and the underlying network. This work presents a novel framework that minimizes inconsistency by optimizing bandwidth usage to deliver useful information. This framework measures the state evolution using an information model and dynamically switches extrapolation models and the packet rate to make the most information-efficient usage of the available bandwidth. The results shown demonstrate that this approach can help optimize consistency under constrained and time-varying network conditions.
A unified context model for web image retrieval
Authors: Yang Linjun , Geng Bo , Hanjalic Alan , Hua Xian-Sheng
Published: August 2012

Content-based web image retrieval based on the query-by-example (QBE) principle remains a challenging problem due to the semantic gap as well as the gap between a user's intent and the representativeness of a typical image query. In this article, we propose to address this problem by integrating query-related contextual information into an advanced query model to improve the performance of QBE-based web image retrieval. We consider both the local and global context of the query image. The local context can be inferred from the web pages and the click-through log associated with the query image, while the global context is derived from the entire corpus comprising all web images and the associated web pages. To effectively incorporate the local query context we propose a language modeling based approach to deal with the combined structured query representation from the contextual and visual information. The global query context is integrated by the multi-modal relevance model to “reconstruct” the query from the document models indexed in the corpus. In this way, the global query context is employed to address the noise or missing information in the query and its local context, so that a comprehensive and robust query model can be obtained. We evaluated the proposed approach on a representative product image dataset collected from the web and demonstrated that the inclusion of the local and global query contexts significantly improves the performance of QBE-based web image retrieval.
A joint layered scheme for reliable and secure mobile JPEG-2000 streaming
Authors: Zhu Xinglei , Chen Chang W.
Published: August 2012

This article presents a novel joint layered approach to simultaneously achieve both reliable and secure mobile JPEG-2000 image streaming. With a priori knowledge of JPEG-2000 source coding and channel coding, the proposed joint system integrates authentication into the media error protection components to ensure that every source-decodable media unit is authenticated. By such a dedicated design, the proposed scheme protects both compressed JPEG-2000 codestream and the authentication data from wireless channel impairments. It is fundamentally different from many existing systems that consider the problem of media authentication separately from the other operations in the media transmission system. By utilizing the contextual relationship, such as coding dependency and content importance between media slices for authentication hash appending, the proposed scheme generates an extremely low authentication overhead. Under this joint layered coding framework, an optimal rate allocation algorithm for source coding, channel coding, and media authentication is developed to guarantee end-to-end media quality. Experiment results on JPEG-2000 images validate the proposed scheme and demonstrate that the performance of the proposed scheme is approaching its upper bound, in which case no authentication is applied to the media stream.
User-Experience from an Inference Perspective
Authors: van Schaik Paul , Hassenzahl Marc , Ling Jonathan
Published: August 2012

In many situations, people make judgments on the basis of incomplete information, inferring unavailable attributes from available ones. These inference processes may also well operate when judgments about a product’s user-experience are made. To examine this, an inference model of user-experience, based on Hassenzahl and Monk’s [2010], was explored in three studies using Web sites. All studies supported the model’s predictions and its stability, with hands-on experience, different products, and different usage modes (action mode versus goal mode). Within a unified framework of judgment as inference [Kruglanski et al. 2007], our approach allows for the integration of the effects of a wide range of information sources on judgments of user-experience.
Teamwork Errors in Trauma Resuscitation
Authors: Sarcevic Aleksandra , Marsic Ivan , Burd Randal S.
Published: August 2012

Human errors in trauma resuscitation can have cascading effects leading to poor patient outcomes. To determine the nature of teamwork errors, we conducted an observational study in a trauma center over a two-year period. While eventually successful in treating the patients, trauma teams had problems tracking and integrating information in a longitudinal trajectory, which resulted in inefficiencies and near-miss errors. As an initial step in system design to support trauma teams, we proposed a model of teamwork and a novel classification of team errors. Four types of team errors emerged from our analysis: communication errors, vigilance errors, interpretation errors, and management errors. Based on these findings, we identified key information structures to support team cognition and decision making. We believe that displaying these information structures will support distributed cognition of trauma teams. Our findings have broader applicability to other collaborative and dynamic work settings that are prone to human error.
Supporting Personal Narrative for Children with Complex Communication Needs
Authors: Black Rolf , Waller Annalu , Turner Ross , Reiter Ehud
Published: August 2012

Children with complex communication needs who use voice output communication aids seldom engage in extended conversation. The “How was School today...?” system has been designed to enable such children to talk about their school day. The system uses data-to-text technology to generate narratives from sensor data. Observations, interviews and prototyping were used to ensure that stakeholders were involved in the design of the system. Evaluations with three children showed that the prototype system, which automatically generates utterances, has the potential to support disabled individuals to participate better in interactive conversation. Analysis of a conversational transcript and observations indicate that the children were able to access relevant conversation and had more control in the conversation in comparison to their usual interactions where control lay mainly with the speaking partner. Further research to develop an improved, more rugged system that supports users with different levels of language ability is now underway.