Thoughts on making Cycles into a spectral renderer

I’ve also compiled a new build for macOS.

CUDA support was not working apparently, so I tried it again. Feedback is appreciated!
(Edit: It doesn’t work. I’ll try it again in the near future on an older Mac system.)

I noticed a new bug in the Camera Response Function widget. After launching Blender, the curve does not show any handles. Clicking and dragging the curve causes the view to behave incorrectly (see screenshots below). This issue goes away when you add a new object and create a new material or when you switch to the “Shading” workspace.

Screen Shot 2020-09-11 at 16.40.31
Directly after launching Blender

Screen Shot 2020-09-11 at 16.40.41
After dragging the curve

Both of those bugs are from the master branch. There are no handles in other curve widgets as well.
image
The curve disappears after dragging because Blender merges handles that are close, but for some reason, it merges all but two. I’ll try to fix this one at some point.

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The OptiX build issue still remains.

A new build is available. Changes:

  • Fixed wavelength sampling with Sobol pattern issue
  • Updated Blender
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The new build is also available for macOS on GraphicAll.

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Nice to see that spectral rendering for Cycles is progressing. Maybe this could be the next technique to push Cycles rendering realism?

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If it’s okay to ask here, I’d like to know if there is chance of this being merged to mainline blender anytime soon? I mean like late 2021 or early 2022 (blender 3.0-3.3 maybe?) or is this something that’s still many years off. If this is something that might not be implemented in the core blender, what will happen to the project then?

I just want to get an idea of what the state of project is, I’m not trying to annoy anyone, or push anyone to work faster or anything like that. If this is the wrong place to ask this I’m sorry.

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Absolutely it’s okay to ask that here. I don’t think the core feature set is many years off being complete. If worked on consistently by a few knowledgeable developers, I think this could be ready next year. The decision of whether or not to merge this is still ultimately up to the Blender developers themselves since bringing on new code brings on new complexity and maintenance cost. I personally don’t have enough time and resources to dedicate to this in order to get it merged and to continue to develop new features at a reasonable pace by myself, but the contributions of @pembem22 have been absolutely fantastic, making it much more feasible that this could get merged some time. If any more developers are considering helping out, this could be ready relatively soon, I suspect.

Please don’t hold your breath waiting for it to be merged, but with some contributions and momentum, I’m sure we could get there.

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A new build is available on GraphicAll. Changes:

  • Baking should work now
  • Updated Blender
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Also available for macOS now: GraphicAll

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Thanks for your support by making these builds available on MacOS!

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A new build is available on GraphicAll. What’s new:

  • Branched Path Tracing is now working
  • Updated OCIO config to be more compatible with already existing files. Colorspaces were renamed to match those from the master branch to avoid wrong colorspaces being assigned to the textures. Render results should now be much closer to the original ones out of the box.
  • Fixed crash during light initialization
  • Updated Blender
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Hi, I follow with great interest this topic even if parts of the technical stuff are beyond my knowledge and I want to share this Two Minute Papers presentation about new(2020) research on light transport simulation that could be at least inspiring for this project.

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That’s quite an unrelated change to Spectral rendering although yes, I’d also love to see something like this in Cycles. The question is whether it’s compatible with Cycles’ light-path- and node-based architecture, which apparently was the biggest issue with stuff like this in the past.

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@pembem22 something appears to be wrong with the 7zip of the latest build

I’ve just downloaded the 7zip and it extracted and launched without any problems. Try re-downloading it, if that doesn’t help I’ll reupload the file.

Just tried re-downloading in case that was it a second ago and it happened again :-/

I’ve repacked and uploaded the build, this should hopefully work now.

Thanks it works now!

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I think you mean: https://www.youtube.com/watch?v=Popg7ej4AUU which displays results by Zeltner et al (students of Wenzel Jakob). You can find the (prepub) paper “Specular Manifold Sampling for Rendering High-Frequency Caustics and Glints” here: https://rgl.epfl.ch/people/wjakob

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