Hi;

(Coming from a Renderman RIS background, which has its own notions of how to do this), I'm curious what the ‘most correct’ way to render multiple mixing fluids (or, what Renderman calls a Heterogeneous Volume) in Mantra is. A simple use case is cream in coffee, or ink in dyed water. The two fluids have different attenuation/singleScatter/HG Phase coefficients, which I'd like to vary across the volume.

The Physical SSS shader VOP, for example, seems to contain the most complete interior/volume control set (attenuation/singlescatter albedo/phase controls presented as both Artistic and Coefficient-based), but it seems not-quite-right to use subsurface to represent this.

Or, I could refract a volume that has varying color/density, but there doesn't seem to be a volume shader node that allows me to vary HG phase, nor would I be able to volumetrically-vary attenuation in that case (attenuation is a surface property of the refraction lobe).

Might anyone have some advice about how do set this up properly?

Thanks
–a