Cycles: Use stochastic sampling to speed up tricubic volume filter

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Stochastically turn a tricubic filter into a trilinear one. This
reduces the number of taps from 64 to 8. It combines ideas from
the "Stochastic Texture Filtering" paper and our previous GPU
sampling of 3D textures.

This is currently only used in a few places where we know stochastic
interpolation is valid or close enough in practice.
* Principled volume density, color and temperature
* Motion blur velocity

On an Macbook Pro M3 with the openvdb_smoke.blend regression test
and cubic sampling, this gives a ~2x speedup for CPU and ~4x speedup
for GPU. However it also increases noise, usually only a little. Equal
time renders for this scene show a clear reduction in noise for both
CPU and GPU.

Note we can probably get a bigger speedup with acceptable noise trade-off
using full stochastic sampling, but will investigate that separately.

Pull Request: https://projects.blender.org/blender/blender/pulls/132908

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This commit is contained in:

Brecht Van Lommel

2025-01-11 04:42:13 +01:00

parent 4c25b49875

commit 646dc7fe4d

12 changed files with 256 additions and 96 deletions

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