Shiny volumes

[adrian_camarena]

I was wondering if its possible to create shiny volumes for like foam or whitewater, so it has some specular highlights. I can create like a custom normal based off the gradient for the volume with the vdb analysis node.

[glacierise]

Hi Tarin,

Good to see you here Shiny, i.e. specular component for volumes - not supported by the volume shader yet, unfortunately. You could surface your whitewater and use a layered scattervol/vraymtl shader where the first one provides the volume, and the second one - the reflection, you'll have to make it transparent by refraction = 1, refractive IOR = 1, unlock separate reflection IOR and add in the reflection. That's a surface and not a volume, but works for us with foam, and only misty parts get rendered as volume.

[adrian_camarena]

When I VDB mesh the whitewater for foam, the scattervolume turns black. I think it's because its more picky about having a perfect mesh since its using some more bruteforce solution to calculating scattering. Any tips on fixing the mesh so it works with the vray scatter volume shader?

[adrian_camarena]

Using particlefluid surface operator directly on the particles seems to create a good mesh and it works now. Vs what i was doing before using the particles to create a volume and then converting the volume to a mesh with "Convert VDB". Thanks! Hristo

[glacierise]

Black maybe means that the mesh is not closed? Which might happen if you're using the fluidsurface HDA which does a bunch of operations, but with the basic vdb from particles/convert vdb to mesh you should always be getting a closed surface and that should work well with the scattervol shader.

[ronald_a]

Funny enough if I remember correctly, it was possible to render volumes (sdf vdbs) in maya vray as a surface (with the volume grid)... wondering how difficult it would be to port over.

[glacierise]

Oh really? I haven't heard of vray rendering these, that would be great to have

[ronald_a]

I would have to doublecheck, but I'm pretty sure. It might also be only possible if you have phoenix FD (in Maya). I believe they initially used that (or maybe even still do) to render fluid bodies.

[glacierise]

Or it does some iso surfacing - I'll look up

[ronald_a]

ok, so I checked in maya and it works with the standard volume grid - just put a sdf vdb in, set to houdini fluid preset and apply any surface shaders. I think initially it meshes the volume (on import for the viewport and again on rendertime). I beliefe if you set the rendermode to isosurface it renders the volume directly.

[glacierise]

Could be that it's Maya and not V-Ray that's meshing it?

[ronald_a]

unlikely. don‘t think there is any function in maya that meshes vdbs (except for bifrost maybe, but this worked before bifrost was a thing, its also not loaded here)