In one of my projects, I have set my compositor such that it has a multi-pass denoising system. In this project, I am not using any transmission or volumetric related assets, so I did not use those passes in the compositor (to cut down render times). I have the max bounces set to the following:

  • Total: 12
  • Diffuse: 12
  • Glossy: 4
  • Transmission: 0
  • Volume: 0
  • Transparent: 6

I was experimenting with the Transmission and Volume bounce #s because I was curious if it would do anything, and sure enough, when I increased the number of bounces in the Transmission pass, it would change the brightness of the flowers in my project. I tried out more values, and as the Transmission value increased, the flowers would get brighter, until they plateau'd at around 9-12.

The flowers I used in this project were part of the free Plant Library by bd3d that is used all over the Blender community. I was thinking maybe the flower assets themselves had implemented Transmission values into the textures, but I'm still confused because the Compositor has absolutely no Transmission input whatsoever. If it is true that the flowers use Transmission bounces, I would expect the flowers to be nearly black?

In all, I'm just trying to understand if it matters whether or not the passes actually exist in the Compositor in order for light bounces to affect the final render. Also, any other information or tips about how the bounces work would be much appreciated. Thank you!

Render with 0 Transmission bounces Render with 0 Transmission bounces

Render with 4 Transmission bounces Render with 4 Transmission bounces

My Compositor with the multi-pass denoising process The portion of my Compositor with the multi-pass denoising process



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