Final Gather does not need photons. Rays are cast for points at different parts of the scene and sample the colors of the objects the rays hit. The color information is sampled back to the starting point of the ray and then the color information is averaged.
Digital Tutors has a great tutorial on this: http://www.digitaltutors.com/11/training.php?vid=4339&autoplay=1
These are the results of a simple portal light test. The only light is a Physical Sun/Sky node that ware placed as the environment on the camera. Then a portal light was placed in the opening and used to pipe the light in from outside.
How to add an environment fog to a mental ray scene
By default the environment node reside in the Maya software render settings, under render options Once you create the node, mental ray will respect it in rendering
This tip found at: http://mayastation.typepad.com/maya-station/2010/03/how-to-add-an-environment-fog-to-a-mental-ray-scene.html
Can't believe it's been just over a year since my last post here. Figured I'd make use of this blog by linking important findings in the Maya world here. Today I found a script online that lets particles emit fluids on Maya.
I found the script at this address on the Area: http://area.autodesk.com/forum/autodesk-maya/dynamics/emit-fluids-from-particles/