Hi hi!

Do you have some inspiration on how you would create this kinda effect in houdini on clouds?

A hacky way would be to render slightly different volumes with color filters on the lighting and then recombine them in post. Aside from some scientific spectral rendering, I'm not sure if there's another way.

Or try surfacing the volume and applying a transparency with dispersion set fairly low or possibly thin-film (in karma's default material, anyway). For Cloud iridescence [en.wikipedia.org] this effect doesn't really happen in clouds thick enough to show their volume from the viewing position, it's the same with circumhorizontal arcs [en.wikipedia.org] except those could probably just use a repeating mixed color texture since the color ordering is always the same relative to the sun.

This is just karma XPU transmission from some fruitless tests trying to get rid of the dicing errors in the shader ball object (before I realized that the normal map from Radeon Prorender I was using was screwy and had ringing artifacts built-in, which created a neat fresnel effect but made the displacement impossibly complex to dice properly.



I'd think with a bright sun backlight at the right angle and some proper cloud geometry you could get similar effects. You might just be able to keep the volume shader and kill all specular and base color on a surface and get something like this showing up on the near side from the backlighting but you'd have to mess with it. You need a fairly complicated surface to get the dispersion to propagate around like this so the render time of doing it the "real" way might not be worth it vs faking it.

Ignore the noise, I was mainly focusing on dicing.