ok, i used to be able to do this...but now, for some dang reason, it never works.
what i am doing is rendering a scene in mental ray...then compositing software rendered paint effects into the scene (in photoshop)
ok...the problem is that i can no longer get it so the paint effect shadows appear in the alpha channel. when i render, i assign a Use Background shader to all the geometry and i use depth map shadows and tell the paint effects to cast shadows. i also put the fake shadows to None.
the closest i can come to getting the results is where every objects shadows appear in the alpha w/ the paint fx. i didn't think i had to go in there and turn off cast shadows for every singel object......i could have sworn the Use Background shader simply did just that......used whatever the background is....and recieve shadows.
can somebody please straighten me out here....this is driving me nuts.
sorry for the rambling....
casey