2025-04-15 Render & Cycles Meeting

Meetings
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Attendees

  • Brecht Van Lommel (Blender)
  • Weizhen Huang (Blender)
  • Thomas Dinges (Blender)
  • Nikita Sirgienko (Intel)
  • Michael Jones (Apple)
  • Patrick Mours (NVIDIA)
  • Sahar A. Kashi (AMD)

Notes

  • Ongoing Cycles development
    • Texture cache prototype is being worked on.
    • Volume sampling continues to be refined, various bugs are being fixed.
    • OSL custom cameras are ready, will land soon.
    • Adaptive subdivision needs some improvements to dicing, and a revamp of the options. After that it can be made non-experimental.
    • Vulkan and Metal graphics interop is nearly ready.
  • Nikita looks into an Embree upgrade for Blender 4.5. This would need to be done in the next two weeks, as the platform team aims to get libraries upgraded by the end of the month.
  • Sahar sent a HIP SDK that should be able to build both HIP-RT and OIDN. Once Blender developers test it works it can be made public.
  • HIP-RT has a bug with curve transparency. The issue is the optimization to accumulate transparency during tracing, without recording hits. This doesn’t work with spatial splits. Could happen with other GPU backends as well.
  • There is a potential bug in Linux AMD drivers in a recent kernel release. Waiting for more details and confirmation to investigate.
  • Short discussion about OptiX OSL optimizations. Closures are a significant bottleneck, though unclear what to do without changes to OSL itself.
  • Question about GPU side scheduling plans. We suspect CPU side scheduling is one of the bigger bottlenecks currently. No work has been done on this so far, but it would be welcome.

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.

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Is the upgrade under consideration the current Embree v4.4.0?

It looks like there are some significant render speed gains!

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Yes, Embree 4.4. Though the Embree release notes don’t seem to mention any optimizations that would benefit us, it’s mostly about stability issues for Intel GPU rendering.

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