Hi Everyone, did a search and couldnt find anything about this:

I have a scene with a cloud (a volume) with a billowy smoke shader and i have raindrops (Flip fluid generated from geometry with lots of copies).

I would like seperate passes of the cloud and the drops, but i can't figure out how to do it so the drops are properly occluded - i mean, if half a drop is in the cloud only the half out of its rendered - is that possible / is this the right way to approach this kind of scene?

I'm probably missing a simple solution so forgive me if its obvious!


~ Craig

I might be mistaken but I think you can assign the standard matte setting to the volume and it behaves properly i.e. still uses the shader to determine where there's smoke and where there isn't, then mattes it. Under Render/Shading/Matte Shading on the Volume object.

Cheers,

J.C.

Hmm that is close, but i've attatched two tests i did - one with the volume matte shaded and the other normal. The matte shading seems to block it out too strongly and totally hides the drops that should be slightly visible still :?

Something nagging at the back of my head about a new feature in H11 that might help with this, but it's not taking. Anyway, take a look at Deep Camera Maps in the help, this will definitely accomplish what you want, although it tends to be somewhat of an elephant gun. You might want to scan through the new features in 11 first just to eliminate whatever I'm remembering…

Cheers,

J.C.

I had the same problem some times ago, and I got this answer from support:

“It's not possible to match the matte volume density to the density on the surface shader. The matte shader uses a default density of 50 to match the default value on the VEX Volume Cloud shader.
To use a different density for matte shading you can add the ”Matte Shader“ (vm_matteshader) property to the torus object, create a VEX Matte shader, assign the shader to the matteshader setting, then change the density on the VEX Matte shop. ”

Actually, I just added a matte option to my shader witch outputs only opacity:
Cf = 0;
Of = newOf;
Af = 0.0f;

That works in houdini10.0, and will work in 11.0. Maybe there is now a new way to do this in houdini11.0.

Cheers,
Claude

Thanks a lot guys, i'll give these a try!