Ken Cecka wrote:
> 
> ...
> This ought to yeild a sphere of radius one, but gives me nothing.
	I just had a similar problem: I was trying to make a rounded box and
used:
isosurface {
  function { "rounded_box", <0.5> }
  contained_by { box { -<1, 1, 1>, <1, 1, 1> } }
}

	Then I rendered it with +D +SP4. During the two preview passes, my
rounded box was visible, but it vanished on the final pass! I then tried
to declare the function:
#declare Func = function { "rounded_box", <0.5, 1, 1, 1> }
isosurface {
  function { F }
  contained_by { box { -<1, 1, 1>, <1, 1, 1> } }
}

	An got the same result. Finally I used:
#declare Func = function { "rounded_box", <0.5, 1, 1, 1> }
isosurface {
  function { F (x, y, z) }
  contained_by { box { -<1, 1, 1>, <1, 1, 1> } }
}

	And it worked. (I had already noticed before that simply adding noise3d
to a function caused problems while adding noise3d(x,y,z) worked as
expected).

	To conclude:
* for your problem, try adding explicit arguments to your functions;
* this looks a lot like a bug. Maybe somebody who understands the code
for isosurfaces and functions (I tried to look at it, but didn't have
the time to understand exactly how it works) should look at it a little
more closely...


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