Mental ray shadow pass on render layers...? Use Background?

[katsu]

Hi guys-
I can't seem to get a shadow rendered from my scene without using Software Render, as opposed to Mental Ray with Sun and sky.
I have a lovely scene with Physical sun and sky - lets say one object and the ground that it is casting the shadow upon. I would like both the final gather shadows (AO I guess) as well as the actual shadow cast by the SunDirection light to live on it's own render layer.
For some reason, applying "UseBackground" to the ground object with shadow mask on doesn't capture the shadows... though it does capture the AO or final gather cast by the object.... Help....?
my work around: I can accomplish this in Maya Software: apply Use background to both, and duplicate the sunDirection light and turn on Depth map shadows...but that sucks!
any suggestions greatly appreciated.

[cyberjunglist]

Hi Cameron, 

I was searching for a solution to exactly the same issue when I saw yr post but no replies..... In the meantime I've found a great tutorial that uses 'mip_shadowmatte' texture which works with mental ray rather than 'use background' which only works with Maya software. 

the shaders he's using in this tutorial are bundled with Mental ray but you need to do some jiggery pokery to get them to work in maya but there are quite a few web tutorials explaining the process.

Hope that's a help.

Matt