Door mask uses mask material's pass index instead of geometry's

[spacek531]

When using a mask object to create door sprites, the background sprite will be colored based on the pass index of the mask's material. It should use the geometry's material's pass index as the pass index of the geometry.

[spacek531]

This requires at least two render layers:

• render layer with the door model and the door mask
• render layer with the door model without the door mask

The material index pass will have to be copied from the second render layer and applied to the first.

I don't know exactly how this can be done.