Interactive RayTracing of Dynamic Scenes

Raytracing of dynamic scenes requires not only fast ray traversal, but also fast update of acceleration structures. Fast ray traversal is usually achieved through traversing several rays at once in a packet. Update of acceleration structure can be done by gradually refitting the structure or by rebuilding it from the scratch every frame. The latter approach puts no requirements on amount or behavior of objects in the scene. In this paper we will describe a raytracing system that combines fast packet traversal with Bounding Volume Hierarchy rebuilt from scratch using approximated Surface Area Heuristic. Vertex culling uses transient frustum in each leaf to quickly eliminate potential intersections with triangles lying strictly outside the frustum. This benefits from large leaves and allows shallow acceleration structure that can be built exceptionally fast with no impact on performance. We will show that combination of these two methods does provide interactive rates even on today’s desktop computers. We will also demonstrate the interactive capabilities on fast relighting of scenes with moving point lights.