I’m using an animation containing a glass window, which I plan to bring into AE to do more work. I was hoping to key through the window, as I’m creating the rain in AE. Is this even possible? Or do I need to just remove the glass and create the glass in AE? The problem with that is, there are reflections of objects in the glass.

Should I do two passes? one with and without the glass? I’d rather not render twice if possible.

Any suggestions would be appreciated.

Couldn’t you assign a unique object (or color) ID to your glass and then use the Object ID render element for your key/mask?

Jeff Patton
My Website | mental ray materials & blog

Sir, you are right, that’s the perfect solution. Sometimes the brain gets a bit too fixated on one approach to the neglect of logic!

Is it possible, now that I’ve spent a day rendering, to render only a matte for an object id without re-rendering the scene?

I resaved my scene as “matte only”, and changed all the materials in the scene to “matte/shadow”, turned all the lights off and rerendered. That seems to work fine, but it seems a bit cludgy - there must be a way to turn off the main render and render the matte only?

Take a look at the render subset option(s) in the documentation.  That may help as well.

Jeff Patton
My Website | mental ray materials & blog

Thanks, that worked. It’s very convoluted, but it worked. Especially since I was using final render to actually render the animation, and final render lights, which don’t work with mental ray. But a few quick changes (turn those lights off), change to mr, and it was good to go.

Hopefully I’ll have to use it again soon so I have some chance of remembering it.