If I render it out with Maya Software, the results come out fine with the two tones. However, when I switch to Mental Ray, the light tone renders out fine, but the dark tone - everything that should be colored where the object is in shadows - comes out just pitch black.

Any thoughts on to why it comes out like that? Again, I haven't touched or change any settings. If I switch the color input to 'Brightness' instead of 'Light Angle', the two tones render out fine in MR, though I'd like to keep it with Light Angle if possible.
Thanks!