Jump to content
Adam Ferestad

Volumes inside geometry not rendering right.

Recommended Posts

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.  


Share this post

Link to post
Share on other sites

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

Share this post

Link to post
Share on other sites

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.  

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now