Back at Fest '06 we milled "arcspiral.ngc" on the mazak. Chris brought back the result, and here's the comparison of a photo and the output of gdepth. The gdepth result is not exactly photorealistic, but it is clearly a very good match to what was actually milled.

Download gdepth here.

Screenshot from gdepth
Photograph of the real thing

(originally posted on the AXIS blog)