Ok, I was thinking about things that might be useful to implement, and I
thought ofmapping objects to the surface of a cylinder or sphere.  Doing
this would simply be a matter of specifying certain of our coordinants to be
rotational (in radians) rather than linear.  Ie, if mapping to a cylinder, x
would be rotation, y radius, z would not change (assuming the direction of
the cylinder is in the z direction).  Similarly, we can map to a sphere by
making two of the coordinants be rotational with the third radial.

Now, there are ways to do this with isosurfaces (I think, but my experience
with isos is very minimal)  using a function which tests against an object
(after transforming coordinants) and returns -1 if inside, 0 if outside, but
I'm not certain isos can handle functions like that (is there a function to
find the shortest distance to the surface of an arbitrary object?  That's
what we really need in this case)

The advantage of doing something like this should be obvious.  For example,
say we have the difference of a torus and a cylinder that makes the up
sloping section (sort of a volcano shape from the inside of the torus). 
I've found these very useful for making smooth curved transitions from a
flat surface to a plane.  With a rotational coordinant mapping, I could do
the same on a cylinder (useful for pipes, mugs, and so on).

So, since I am not a POV guru, does this exist in some form, or is it easier
than I think with iso surfaces?  Do people think this would be a useful
feature?

Geoff

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