Hello guys. I was trying to work with glass material and caustic lights. However I have a problem while creating a material for the plane. The caustic lights and shadows are casted to the plane. So I don't want the plane to have diffuse channel, I just want alpha information for the shadows and alpha information for the refracted light that is bouncing in the floor in a sepparate alpha channel. Is that possible? I need to compo it into a live action footage so I don't want the geometry of the plane to be exported.
I thought this idea could work:
1. Export the whole geometry, the glass balls with the floor.
2. Export direct reflection and refraction passes.
3. Export a CONSTANT COLOR matte of the ground but NOT the glass balls. So that we can crop out the diffuse of JUST the floor in the compositing stage.
This must be super easy and not as this silly work out. How do you composite caustic lights?
Thanks in advance guys.