Sorry folks, I should have explained it more...

HDRI: High Dynamic Range Imaging

It's a way of faking GI using images with a higher dynamic color range than normal imagery.

Here's a buncha links for more info on the study of HDRI:
https://www.debevec.org/HDRShop/main-pages/links.html

Also, below are links to a free plugin called: LightGen, AND a free Program called: HDRShop.

Lightgen is a plugin for Photoshop, I think, that will take an a HDRI image, or any image for that matter, and output a Maya mel script of lighting info for you.
So, when you run it in your Maya scene, it will create lights JUST like you shot your scene in the same environment of your chosen image. ALMOST, instant GI within Maya

HDRShop is a free proggy that converts images into hdri imagery, perfect for use with Lightgen, AND preforms the proper "Polar" distortion for you automaticly.
Also great for environment reflection maps, hdri, etc.

Here is the actual link to HDRshop and lightgen
https://www.debevec.org/HDRShop/

Hope that was a good explanation

Enjoy!