Render Caustics with Alpha channel on Mental Ray

#1

Hi, I’m new to the forum. And I take this opportunity to ask you a difficult question about Maya / Mental Ray 2012 because I encounter a problem that for once I can’t find any answer, even after searching all over the internet.

I want to make a mental ray render with alpha channel in a scene surrounded by caustics. To be more specific, I want to keep the elements of my scene and their caustics but everything else need to be in alpha channel. I just want to embed the render in a video later (Tracking 3d, it’s ok for this part). I try to use a useBackground or Surface material in order to project my caustics, like we could do with a shadow (on the wall and the floor). But despite my many tests, I can’t find the right solution.

If you have an idea or at least one clue, I’m interested! Thanks.

Anthony

Shark

#2

Hello, Gallioth. I don’t think there are any render passes for caustics, to separate them out from the primary render. One solution, albeit tedious, is to use render layers instead. Then you have two complete renderings of course, and it can take twice as long, but at least you have the separated caustics in one.

#3

Hi, InfernalDarkness. Thanks for your answer, it could be a great solution if it’s work, because i already render the beauty pass without caustics of my animation.