Basically they start with a pile of powder and hit it with lasers. The lasers melt the powder and cause it to solidify into the shape they have designed -- it's like ink jet printing, only in 3d.
Googling 3d prototyping finds pages like this ...
http://www.3dsystems.com/products/modelers/index.asp ... where you can buy your very own 3d modeler.
Here's another one:
http://3drp.com/ that actually prototypes in color.
...
And now having watched the demo video on 3drp's site, I'm kicking myself for not coming up with some seed money to buy a dozen of these and going to Blizzard with a business proposition.
This is ridiculously easy.
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