Clearly the volume shader is having no effect at all once the surface shader is plugged in.
All I really want to do is mix the two shaders in some way. Specifically I’m after the effect visible in the first image where the dark object intersects the cube and can be seen for a little distance within the cube. I don’t want something that is just slightly transparent, it needs to have some density so that objects fade away the further the intersect into the object.
Any ideas?
I am on a MacbookAir, and I’m using a 2.70 from 5 March.
Exactly. Presumably there is plenty of volume going on in your render, but you can’t see it because the surface is opaque! Change your Glossy shader to Glass!
If you use a surface shader - it has to be transparent (or semi transparent). So the glass, translucent, transparent and refraction shaders should all work fine with volumetrics.
You can also use a mix surface shader - just so long as some aspect of it is transparent (i.e. you could have a mixed glass/glossy shader - with a texture to control which parts are transparent).