You need a shiny, reflective ball, like a silver Christmas Ornament or a mirror ball. You take your digital camera, and you take pictures of the ball in different exposures, I think 8 is enough. then you take all of those into Photoshop and you make sure the ball is the only thing in the picture, on each of the exposures. Then, you download HDR Shop by doing a Google search for HDR Shop Download, and you use the create HDRI from image sequence, you load all of your exposures, you assemble the HDRI, and then you go to Images-Panorama-Panoramic Transformations- and on the right, you make it a Latitude/Longtitude, with the default size, usually is enough, and you press ok.
then you save that as a .hdr image. I hope you know how to use the HDRI in Maya, right?
hope that helps;
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