Aliased material ID render element - solution ?

[nirsul]

I think that the multimatte will solve this very problem as you can set each additional multimatte to a different ID (be it a material or object) - thus you get a different mask for each - without the blended (AA) area -

Did I get you right ?

NIR

[joconnell]

You are indeed right - the matte itself is totally clean but since the rendered object might be against other objects in the scene in the main render it's going to be much harder to separate than an object that was rendered against a pure colour like black or white. When your compositing app gets to the anti aliased edges it has a harder time trying to unpremultiply them.