For multiple buffer rendering purpose with Mental ray I use the user frames buffers. I both use Mental Ray for Maya and mental ray standalone.
In standalone if I have to specify all buffers I want to use by appending some lines like this:
frame buffer 2 "+rgba_16"
frame buffer 3 "+rgba_16"
In Maya I can tick in "Render Global Settings" which user frame buffer I want to use. But unfortunately I can't find where to specify what king of buffer I want (RGB, RGBA, RGBA_16...). and I need my byffers to be RGBA_16 but they remain RGBA!!
If I specify a mentalrayTextOptions with the correct lines (see above), it doesn't make any differences, I think Maya simply bypass this text when using Mentalray built-in.
Any idea about using user frame buffer on 16bit per channel instead of 8?