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I encountered a very weird behavior with my procedural clouds. For context, I also used VDB clouds, which were full of artifacts where they are intersecting with each other. I found a hacky workaround to this issue, which is to place a ton of transparent planes inside the volume.

Now, as I forgot to hide these planes, I turned on the procedural clouds, and noticed how they appeared completely differently.

Without planes:

enter image description here

With planes:

enter image description here

You can see how these planes are placed in the scene. What also confuses me, is that originally I had a multiply node to increase the density of the clouds, but it didn't really appear to be doing anything. But with these transparent planes, it seems to work as intended.

enter image description here

Does anyone know what's going on here?

Edit:
volume bounces: 2
transparent bounces: 120
volume step rate: 1
volume max steps: 8

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1 Answer 1

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Missing some details here, shaders and light path settings would be useful.

Some experimentation tells me that a transparent plane using Principled BSDF has odd behavior, I'm guessing because it has a lot of surface components in addition to transmission. If you use Transparent BSDF it should be different.

Other potential causes:

Light Paths -> Volumes is default 0

Clamped Indirect Lighting

Step count or step size in volume settings?

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    $\begingroup$ Added these info to the post. I'm using the transparent shader. $\endgroup$
    – Geri
    Commented Jun 8, 2023 at 18:45
  • $\begingroup$ Of course setting Transmission > 0 on a Principled BSDF behaves differently than a Transparent BSDF. Transmission makes the Principled BSDF work like glass and takes the IOR into account and still has reflections, a Transparent BSDF creates alpha transparency (with the difference that you can color it i.e. give the RGB channels individual alpha values). Fully transparent becomes invisible, fully transmissive not. $\endgroup$
    – Gordon Brinkmann
    Commented Jun 8, 2023 at 22:51
  • $\begingroup$ @GordonBrinkmann you're right, I was just tooling around at work while I was on break and breaking the rules on BSE. Hello, btw, feels like a while since I've seen you but I'm sure you've been around $\endgroup$
    – Allen Simpson
    Commented Jun 8, 2023 at 23:00
  • $\begingroup$ @GordonBrinkmann fwiw I did set IOR and it didn't solve the apparent problem of cutting light to volumes or whatever was happening in my test file. It was a long day, lol. Question just says 'transparent planes' and I was trying to determine what that meant $\endgroup$
    – Allen Simpson
    Commented Jun 8, 2023 at 23:01
  • $\begingroup$ Yeah hello, actually when I saw some of your recent posts yesterday I also got the feeling it's been a while :-) $\endgroup$
    – Gordon Brinkmann
    Commented Jun 9, 2023 at 6:33

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