by hda007 on Tue 10. Feb 2009, 16:27
Alright, so using mental ray I can easily render my alpha channel on any object to cut it out of a background. But when it comes to comping and post effects like color balancing, I run into several problems.
For example: I have a car lit with light cards for paint reflections. The ground plane is usually a surface shader for rendering the car itself, but later a blinn is applied for ground reflections.
The first problem I encounter is the alpha channel of the car is nonexistent in the reflective surface. Is there any way to override this? A new shader to use? An attribute to change?
Secondly, when it comes to making a carpaint reflection pass for a ground reflection, I need to make a whole separate pass (surface shader on the car) to fake it's alpha in the reflection because I still get the light cards in the ground regardless if their visibility is turned off. Is there a technique to hide specific objects from a specific reflective surface, but not another reflective surface in one pass?
