2022-11-15 Render & Cycles Meeting


  • Brecht Van Lommel (Blender)
  • Thomas Dinges (Blender)
  • Weizhen Huang (Blender)
  • Christophe Hery (Meta)
  • Brian Savery (AMD)
  • Sebastian Herholz (Intel)
  • Michael Jones (Apple)
  • Patrick Mours (NVIDIA)


Blender 3.4

  • AMD: New Windows HIP compiler received to fix performance regression and enable RDNA3 support, Brecht will install it on the buildbot. Still some practicalities be figured out, will be done over email.
  • Path guiding: some discussion on the equiangular sampling bug and associated patch in the meeting. Seems this is about the best we can do with the current API, even if not entirely correct, and fully fixing it will require API updates. In tests by Sebastian so far this issue did not actually have much of an impact, so should be ok for now.
  • Intel GPU rendering for Metal is now enabled, after patches from Apple and upgrading the macOS builders.
  • Sampling pattern regression being worked on by Nathan.

Ongoing Projects

  • Many Lights Sampling: Weizhen finished implementing basically everything in the paper, including volume support. Adaptive splitting is no longer used, and a new approach with min-max measure for sampling seems to work well. Still there are various improvements possible beyond that, for example taking into account transmission for volume light sampling. Brecht will work on some issues regarding double sided emission on triangles and poor estimations of light intensity with some shader node setups. Hopefully after that this can go into master and get further improvements there.
  • OSL with OptiX: it’s in a pretty good state now, Patrick verified various scenes are rendering with similar results, mainly some expected differences in texture filtering due to no OpenImageIO on the GPU. It’s considered ready enough to get (automatically) enabled when the new libraries land. Contributing patches upstream is being worked on. OptiX support in OSL upstream is still changing often, so some tight coupling between Blender and OSL versions to keep things compatible is likely needed for a while.
  • Apple Metal:
    • Michael submitted a new shader specialization patch, that addresses various issues with the previous one and generally makes a much better user experience. Brecht will review it, impact of this is fairly complex so might take some time.
    • Some prototyping was done to improve CPU + GPU rendering performance, which gave a 5-10% speedup. There is some interest from the BF side in this, though higher priority is multi GPU performance. Need to look at patch to discuss if design approach is right.
    • Various fixes for MetalRT were done, including to make point clouds work. Still various remaining issues to be fixed.
  • Hydra and MaterialX: Brian updated the tasks with the latest design, as discussed at the Blender Conference. The current implementation does not include incremental updates for scene editing, which means the impact on the USD code is limited. However once that gets worked on, some more complex design discussion is likely needed.

Practical Info

This is a weekly video chat meeting for planning and discussion of Blender rendering development. Any contributor (developer, UI/UX designer, writer, …) working on rendering in Blender is welcome to join and add proposed items to the agenda.

For users and other interested parties, we ask to read the meeting notes instead so that the meeting can remain focused.