Maya 2013: user_ibl_env for IBL
Check out this mental ray light node only available in Maya 2013 and up, it is more efficient than a standard IBL setup! (Due to the fact that it doesn’t use final gather, but instead uses direct illumination from the hdr image)
Here’s a quick tutorial at CGTalk.
Just make an area light, turn on “use light shape”, set it to custom, plug the node into the light shader, then plug the image into the node and up the samples. We can use the rotate attribute to turn the image sphere around. Remember to drop the user_ibl_env node into the environment shader of the camera.
For the scene, we have to add a control to the miDefaultOptions. Type “select miDefaultOptions” in command line, add a string “light relative scale” and give it a scalar value of 0.318, This is to prevent any blown out results.