: We present a method that enables fast, per-frame and from-scratch re-builds of a bounding volume hierarchy, thus completely removing a BVH-based ray tracer's reliance on updating or re-fitting. On a dual-2.6GHz Clovertown system (8 cores total), our method renders the exploding dragon model (252K triangles) at around 13-21 frames per second (1024x1024 pixels) including animating the triangles, per-frame rebuilds, shading, shadows, and display. The build itself takes less than 20ms, and is nearly agnostic to the distribution of the triangles; thus, the variation in frame rate (21 fps for the initial, smooth frame, and 13 fps for the timestep corresponding to the fourth image) is due only to varying traversal cost, without any deterioration in BVH quality at all (i.e., when starting with the last frame, the frame rate actually increases). With ray traversal performance reaching the point where real-time ray tracing becomes practical, ray tracing research is now shifting away from faster traversal, and towards the question what has to be done to use it in truly interactive applications such as games. Such applications are problematic because when geometry changes every frame, the ray tracer's internal index data structures are no longer valid. Fully rebuilding all data structures every frame is the most general approach to handling changing geometry, but was long considered impractical except for grid-based grid based ray tracers, trivial scenes, or reduced quality of the index structure. In this paper, we investigate how some of the fast, approximate construction techniques that have recently been proposed for kd-trees can also be applied to bounding volume hierarchies (BVHs). We argue that these work even better for BVHs than they do for kd-trees, and demonstrate that when using those techniques, BVHs can be rebuilt up to 10× faster than competing kd-tree based techniques.
These techniques have originally been proposed for kd-trees, but work even better for BVHs, where small numbers of bins produce BVHs nearly indistinguishable from sweep-based builds REF .
On fast Construction of SAH-based Bounding Volume Hierarchies
2007 IEEE Symposium on Interactive Ray Tracing
2007 IEEE Symposium on Interactive Ray Tracing
Computer Science