I'm not sure about RP for art bronze castings; there are people doing this for industry, but art lags behind a little. There are lots of companies doing this for jewelers, though, on a smaller scale, using wax-like materials that burn out readily to cast gold, silver, and platinum. Here's one in LA: http://rpwax.com/
There are companies that use CNC milling (subtractive rapid prototyping) to make originals for art casting; Kreysler and Assoc. is one. (www.kreysler.com). They typically carve a large piece in urethane foam and surface it with oilclay, allowing the sculptor to determine the final texture. This is then molded, wax is cast into the mold, and the lost-wax process proceeds normally from there.