2022-11-30 Render & Cycles Meeting


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


  • Many Lights: getting close to ready to merge. Weizhen is still cleaning up the implementation, and Brecht works on fixing issues with CUDA, HIP and shadow pass. Various issues were fixed in the past weeks. One remaining weakness is that instancing is not supported in the light tree which can lead to more memory usage than before, but this is not considered a blocker.
  • Path Guiding: Sebastian will make a branch that add support for guiding of glossy reflection. The best strategy for this is not obvious (importance resampling, setting probability based on roughness, …). A test build will be provided so users can help test what works best.
  • Hydra / MaterialX:
    • The required library updates for this are getting closer to ready, MaterialX support is in the VFX platform 2023 branch and the new Rocky Linux builder is on the buildbot. Mainly waiting on all platform maintainers to be available now to do the actual library update.
    • The timeline for landing this in 3.5 is pretty tight, especially since Brecht will be on Holidays in the last weeks before bcon1 ends. Brian will try to get initial patches for review up as soon as possible.
  • AMD HIP-RT: AMD have hardware ray-tracing working internally, but stability and performance are still being worked on and driver support for this still needs to become part of an official release. A patch will be sent to Brecht for early design review.
  • Intel OneAPI: hardware ray-tracing is currently being targeted for Blender 3.6.
  • Metal: various performance patches from Michael are still waiting for review by Brecht, will review as soon as there is time. NanoVDB support for Metal is also being worked on.
  • Hair: Weizhen might start work on implementing her hair BSDF paper in Cycles, Christophe will share their implementation.
  • Principled BSDF v2: Lukas updated the branch, including early support for collapsible panels to organize the many inputs.

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.