Multimatte, Render Layers and Isolating Wrapper Shadows from Object

[gfmarsh]

I have read that you have to render two passes in order to separate a cast wrapper shadow from the object. I guess Multimatte can't really isolate the shadow and object to take into effect motion blur and DOF from a Vray physical camera? I guess I just wanting to confirm this so I not missing a feature somewhere instead of running two render passes. Render Setup sort of achieves this but in effect runs two passes anyhow. Thanks.

[Morbid Angel]

Yeah its correct. You can isolate the shadow and object in one pass, but there won't be any shadow information behind the object since that area is not visible in the primary rgba buffer. So when you blur things you will get edges where object and shadow meet.

[gfmarsh]

Is it an isolation through integer values, where it doesn't take into account the physical camera? I'm not sure what the point is in having a multimatte or object ID passes when it can't go through physical camera first. Aliased mattes aren't very useful.