- [✨ feature request] Why roughplastic's alpha is not differentiable?

[LZleejean]

Summary

Everything is ok but can't optimize roughplastic's alpha.

Description

I tried create two parameters to be optimized which is roughness and diffuse reflectance but failed. Because roughplastic's alpha is not differentiable.

Steps to reproduce

[Speierers]

Hi @LZleejean ,

Please see #391 for this.

Basically those are not differentiable as the roughplastic BSDF pre-computes tables in its constructor, which would need to be updated whenever you update the alpha value. We are still investigating better solutions to also make this parameter spatially-varying.

This being said, with only a few changes, you should be able to turn this member into a differentiable type (ScalarFloat -> Float), expose it in the RoughPlasticBSDF::traverse call back and move the table computation code to RoughPlasticBSDF::parameters_changed() so that it gets updated when necessary.

Good luck!