Compositing Cycles Render Passes in Blender
Why Blender Stack Exchange recommends it
Blender Stack Exchange answerers and commenters link it when explaining how Cycles passes combine into the final image, and how to fix noise or firefly artifacts in the compositor.
Recommended by 2 people across 2 different months, 2016 to 2020.
What it is
A 55-minute CG Cookie tutorial on manually compositing Cycles render passes in Blender, using a product render as the example. It covers rebuilding the final image from diffuse, glossy and other passes, reducing noise per pass, replacing textures with the UV pass, and removing fireflies. It was recorded in an older Blender version, so the interface differs from current releases.
What people said
Recommends Georges D · 2016-07 · Blender Stack Exchange · on “Why are there rectangle shaped glitches when using motion blur problem in Cycles?”
I came through this question accidentally, I found a similar problem in a tutorial about Passes, where he had this issue and explained why and how to fix. This might be due to using Bilateral Blur filter in the compositor, for a pass to remove noise or/and fireflies, if a pixel has a huge color data, Bilateral Blur filter will maximize this pixel to become a rectangle, the solution is to go through a Math node with (Greater Than) factor to get the values down, check the video at 51:30 [this video]
Recommends sambler · 2020-05 · Blender Stack Exchange · on “What are the denoising passes useful for in 2.79 experimental feature set?”
@Leander there is a difference between practical and possible. CGCookie has a tutorial on creating nodes [this video] that combine the base passes to match the final render. Today we have the Denoise Node which makes a simple case for using these.
Cites sambler · 2016-05 · Blender Stack Exchange · on “Rendering single .exr from passes with different shaders?”
The first tutorial lists a number of different shaders that may have their own render pass. Cycles doesn't separate the render result based on the shader used, cycles uses node based materials that can combine many different shader types to get the final result. In cycles the passes that are available will each contain a portion of the scene that when combined makes the final image (or render layer). The way that the passes are combined is shown in the manual [LINK] and has been explained in a few [this video] video tutorials [LINK] . If an object's material has only a diffuse node then all the information for the object will be in the diffuse pass. If it has a mix of diffuse and glossy then it w
Cites Mentalist · 2017-03 · Blender Stack Exchange · on “Paint over Render in compositor”
What I would try is: separate out your render passes [this video] and then recombine them in a way that you have the glossy passes isolated separately from everything else. Because when you paint you will paint the highlights last, on top. I don't think you'll need as many layers as you think, based on the workflows of digital painters I've seen on YouTube. As for doing this *all* in Blender, it might not be worth the hassle, since image editors like Ps, Krita, or even GIMP are probably better suited for this task. I admire your Blender-purist ambition though!