i've often used povray as a decent benchmark. it's not the
best renderer (as duff will tell all who ask), but it
compiles reasonalby and mades good use of floating point.
and models are cross-platform. it's been a good while
since i've compiled it, but i distinctly remember it 
being not nearly as arduous as ghostscript.
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it also has the advantage of being a real app.
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