I am rendering them as a separate pass with all other render elements deleted or turned off. I am also not using an override material as I don’t know what is meant by that. I think I have seen this tab in a newer version of v-ray. Mine doesn’t have it though. Using vray 3.10. I assigned a simple vrayLightmtl to all geometry to speed up the render.
I think I had the same problem earlier when I rendered zdepth passes for several shots because they were incorrectly setup by a teammate. I researched this a bit and concluded this should be pretty aliased as otherwise the zdepth information would be wrong but now in comp I get jaggy edges in some occoasions especially when using a zdpeth as rgbg to fake fog for example. As we also rendered motion blur this doesn’t mix at all. So i’m thinking there is still something wrong with it somehow. This is a different problem and shot though.
The original scene i was talking about can be found here
https://dl.dropboxusercontent.com/u/67064404/S4S9\_MatID\_vray.rar