GPU rendering and matte object

[Anonymous]

I have read that you cannot use a matte (holdout) object if you are rendering GPU. Not interested in shadows, just want a matte object. Has this been dealt with? Shocking, all I want is an object to basically render a black alpha.

Does anybody have a workaround that doesn't involve a second render pass just to get an alpha for my scene?

[Stephen.Blair · Accepted solution]

That's right, matte (the matte parameter on a shape, the matte shader, and the matte parameters on a standard_surface) are not supported yet on GPU.

How about a custom AOV where you output black for some objects, and white for all the rest? That's doable. But if you have partial transparency, that's more complicated.

[Anonymous]

actually, I just tried that out last night and it worked like a charm. Perfect!!!