Lecture 09: Acceleration structures

Bounding volume

Axis-aligned bounding boxes

Box intersection algorithm

float3 invRaydir = float3(1.0) / ray.direction;
float3 t0 = (aabb_max - ray.position) * invRaydir;
float3 t1 = (aabb_min - ray.position) * invRaydir;
float3 tmin = min(t0, t1);
float3 tmax = max(t0, t1);
return maxelem(tmin) <= minelem(tmax);

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Bounding volume hierarchy

• Top-level accelleration structures (TLAS)
• Bottom-level accellecration structures (BLAS)

“Acceleration structures” experiment

TODO

• Group traingles to objects
• Compute axis-aligned bounding boxes
• Change intersection flow to use AABBs
• Implement two-level AS
• Implement traversal of the BVH

“Acceleration structures” experiment

Reference

“Acceleration structures” experiment

What is the new knowledge?

• Traversing AABB before internal triangles gives a good speed up
• BVH don’t speed up a Cornell box