Volumes inside geometry not rendering right.

[Adam Ferestad]

I'm trying to render out a volume inside of a clear object and running into an odd materials glitch.  To test I have created a box with a default glass principle shader and a VDB volume of the same box shrunk down inside the box which I have colored blue.  Rendering with Mantra, if the volume is inside glass box, it loses all color, but outside keeps it.

There is one other issue.  I really want the volume to filter the light to color, so the shadow/rays coming out of the volume should be roughly the same color as the volume, as opposed to being black.  

volumeTest.hipnc

[anim]

it's because box is casting shadows on the volume

by default glass material doesn't allow light through, you can either enable Opacity/Fake Caustics on your glass shader for fast approximate

or allow All Paths on Mantra/Rendering/Shading/Allowable Paths, but I wouldn't recommend that as it is not only slow and extremely inefficient for uni-directional pathtracer like Mantra, but you'd need to have Volume Limit set at least to 1, which is additional performance hit, so I'd stick to fake caustics

[Adam Ferestad]

THANKS!!! From the few buckets that I have finished it looks like the fake caustics are doing the trick and actually producing the look that I want.  The volumes + the shader are definitely going to be a pretty major performance hit, but I am planning on using this for a still for the time being, so it's not going to be too bad right now.  Unfortunately for what I'm doing I need to have my volume limit at at least 1 anyway, so yeah.... sucks to be me, lol.  Anyway, thank you so much.

I am going to try the second approach you mentioned as having multiple solves for an issue is never a bad thing, and I'm sure there are instances where even with the performance hit it is the right way to go.