export vdb/volume normals

[Anonymous]

Hi !

is it possible to export volumes/VDB normals, like this volume normals they use in this tutorial ?

https://www.youtube.com/watch?v=cjvw18aRQtM&t=1s&ab_channel=ActionVFX

[peter.horvath6V6K3 · Accepted solution]

You can not render a normal pass of vdb volumes directly. If you create a volume from a mesh, you can render the mesh normals. Or if your VDB contains a normal channel (not sure how common is that tbh), you can read it via a volume_sample shader and write it to a custom aov via the aov_write shader.

[Anonymous]

Yeah I was pretty surprised too while watching this video as volume isn't made of vertices so technically it shouldn't have normal maps, but somehow those volume they use have one.

anyway it was mainly out of curiosity, as it bring another level of compositing control, thanks for answer !

[schwungsau]

they use an RGB light rig, the best way to relight your volumes.
3 distance light, for each XYZ axis with Red for X, Blue for Y, Green for Z. --> you render the volume 2 twice with normal volume and shader/lights and "non-emission smoke shader" and with RGB lights.