So Blender's compositor denoiser is pretty swell, but sometimes you want a bit more control over the end results. I built this node to help out. It handles each render pass separately, and makes it easier for you to pull out the passes you want to work with. Each pass -- diffuse, gloss, subsurface, etc -- are denoised separately and have faction options so that you can output only the passes you want to use. All passes are combined using the same methods as Blender does internally, except where documentation was unavailable. There is also the option to disable denoising if that isn't your thing, so that this can be used as a quick and dirty pass combiner node.

"What's the point?" you might be asking. In the case of denoising, I've found that denoising each pass separately provides more consistent results, with less denoising artifacts. This is especially true when working with volumetrics, which consistently muck up the other passes when denoised as one. When using this node, each pass lighting pass also uses that pass's color data as the denoising albedo, which should contribute to better results for that particular pass. Mind you, my observations are not scientific, but feel free to compare for yourself. If not denoising, working with render passes can get messy fast. This node can give you a quick one-node solution to getting all of the passes you want combined while only using one node to do it. This gives you horizontal breathing room to work with whatever passes you need to handle separately. The less time you have to spend on combining and separating out passes yourself, the more you can spend on the actually cool stuff you can do in the compositor, like bloom and post-process dof or whatever it is that's popular right now.

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Changes

• 9 January 2021 - Addressed an issue where transmission materials, such as glass, could be darkened by the denoiser node. Also removed the pre-2.9 version, since I have reason to believe 2.9 users were accidentally downloading it.

• 10 October 2020 - Redid the entire node. Blender removed the Subsurface outputs a few versions back, so I've also removed them. Node can now output individual denoise passes as-needed, and should perform better when passes are disabled. Since older versions of blender will still have the Subsurface render layer passes, I've left the older version up for people on those versions.

• 15 March 2020 - Fixed an issue on Emission, Environment, and Volume passes where if they contained no data, they would produce incorrect artifacts.