Karma LPEs and the RenderMan Denoiser (Patreon)

Several members have asked about the workflow for denoising custom Karma LPE AOVs with the RenderMan denoiser. Here's how to do it!

First, get up to speed on the RenderMan denoiser workflow in Solaris by reading my first article on the topic: https://www.patreon.com/posts/108016869 This will get you rolling with the basic general setup.

We'll add to this by creating a new render settings node with a new LPE. In this case I made an LPE from the right side light in the scene.

The important thing is we want to save only this AOV as a separate file. No alpha, no diffuse, no variance information, just the one AOV. I attached another ROP and saved the image to disk in the same folder as the main render.

The RenderMan denoiser allows assignment of a particular denoising pass to arbitrary AOVs. In the denoiser GUI, open the folder containing the two EXRs: the main render with all the variance information and base AOVs and the second, single-AOV file. The GUI should show the two files, with the second one's icon slightly darker grey.

Next, click the gear icon and choose a denoising pass to assign to "light_right."

I tried diffuse, specular, color and albedo and each gave quite different results. I don't know if there is a "recommended" approach here. It's probably a matter of trial and error depending on the contents of your LPEs. The color denoiser pass gave the best result (logically so, since it's a beauty pass from one specific light). Specular is too noisy and diffuse and albedo are all wrong.

Conclusion

There you have it! The RenderMan denoiser demonstrates its power and flexibility once again by allowing us to easily denoise our custom Karma AOVs. Thanks for the questions everybody, I hope you found this useful!