Cycles: fully decouple triangle and curve primitive storage from BVH2
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Authored by Brecht Van Lommel (brecht) on Oct 6 2021, 3:53 PM.

Details

Reviewers

Patrick Mours (pmoursnv)
William Leeson (leesonw)
Sergey Sharybin (sergey)

Commits

rC1a7a07a3930d: Fully decouple triangle and curve primitive storage from BVH2
rB04857cc8efb3: Cycles: fully decouple triangle and curve primitive storage from BVH2

Summary

Previously the storage here was optimized to avoid indirections in BVH2
traversal. This helps improve performance a bit, but makes performance
and memory usage of Embree and OptiX BVHs a bit worse also. It also adds
code complexity in other parts of the code.

Now decouple triangle and curve primitive storage from BVH2.

Reduced peak memory usage on all devices
Bit better performance for OptiX and Embree
Bit worse performance for CUDA
Simplified code:
- Intersection.prim/object now patches ShaderData.prim/object
- No more offset manipulation for mesh displacement before a BVH is built
- Remove primitive packing code and flags for Embree and OptiX
- Curve segments are now stored in a KernelCurve struct

Diff Detail

Repository

rB Blender

Branch

prim-refactor (branched from master)

Build Status

Buildable 17597
Build 17597: arc lint + arc unit

Event Timeline

Brecht Van Lommel (brecht) requested review of this revision.Oct 6 2021, 3:53 PM

Brecht Van Lommel (brecht) created this revision.

Harbormaster completed remote builds in B17597: Diff 42971.Oct 6 2021, 3:53 PM

It's not great to make CUDA slower, but in a way this is the legacy code path and Embree and OptiX are what most users use, so it seems like a good trade-off to me.

Some graphs:

Brecht Van Lommel (brecht) mentioned this in T91770: Cycles X baking with Cuda.Oct 6 2021, 4:17 PM

Brecht Van Lommel (brecht) mentioned this in T91968: Baking lighting for transformed objects is broken (3.0).Oct 6 2021, 4:34 PM

I've got similar relative comparison of CUDA/OptiX on RTX6000.
Think is better to aim to a hardware-supported ray intersection and optimize our code for that world.

From reading the code and testing it didn't see anything wrong.

This revision is now accepted and ready to land.Oct 6 2021, 5:09 PM

LGTM too.

Closed by commit rB04857cc8efb3: Cycles: fully decouple triangle and curve primitive storage from BVH2 (authored by Brecht Van Lommel (brecht)). · Explain WhyOct 6 2021, 5:53 PM

This revision was automatically updated to reflect the committed changes.

Brecht Van Lommel (brecht) added a commit: rB04857cc8efb3: Cycles: fully decouple triangle and curve primitive storage from BVH2.

Raimund Klink (Raimund58) awarded a token.Oct 7 2021, 10:52 AM

Brecht Van Lommel (brecht) added a commit: rC1a7a07a3930d: Fully decouple triangle and curve primitive storage from BVH2.Jan 27 2022, 11:29 PM