Regarding Render Passes in Maya...
its actually quite simple to take out render passes in maya. Well as we knw there are passes like Diffuse,Specular,Shadow,Reflection and Occlusion.These at the end get composited to get the final Image tht we call Beauty Render.
Anyways I will like to help u for getting render passes.
1. When ever u create a render layer you can see a Flag Visible on the Left of the layer name.
2. Click on that and scroll down, u will find Render Pass Option:
3. By Default Beauty is ticked on....so it will render the frme usually as u render the frame.
4. To check..tick that off and jst click Diffuse ON....n render. It will render a flat pass with no shadow or spec........this is called Diffuse Pass.
5. Same way u can tick diffuse off and ON spec or shadow. U will get those renders.
6. But this is a way to check the passes in Current Frame Render. If u tick Diffuse, Spec and Shadow ON n then render through Batch Render the u will get those 3 passes rendered and then whn u composite thm u will see the same render as u rendered the beauty pass..
Thr are many more passes that we require depending upon the use...but its actually difficult to write here n xplain them so...for now jst try this way n kindly take help frm the Web.
Just try this way n stiff u have any doubts regarding this thn do reply.....
all the best.