Hey Karel,

I was just searching for a solution to the same problem when I came across your post. It dawned on me that the AO shader in mental ray allows you to set the “Type” to normals by typing the number “3”. Just set it in a mental ray shader’s “Surface” channel and putting that material in “Material Override” channel in the “Processing” tab. If you don’t want to go the mental ray route you could always render the RPF 2X the size of your output and scale it 50%. That gets rid of some of the aliasing.

The bad news is, as far as I know, there are no plug-ins or add-ons that give you an option to render that element. RPFs rendered in max alias’ in After Effects but not in Combustion. Go figure.