[PLUG] attention geometry geeks

[Rich Shepard]

On Wed, 28 Apr 2004, Russell Senior wrote:

> I am looking for an elegant way of computing the nearest distance from an
> arbitrary point P to a surface.  I have solved the simple cases (for
> primitive shapes box, cylinder, sphere, toroid), but this one is slightly
> more complex.  The case I am concerned about involves the removal of a
> sphere of radius r and center point Q from those surfaces.  Obviously, if
> point Q is not less than distance r from the surface, it doesn't remove
> any material.  And in general, I only care about cases where point Q is on
> or above the surface of the primitive.
>
> Any pointers, ideas, solutions?

Russell,

  You may want to read the chapter on convex hulls in de Berg, M., M. van
Kreveld, M. Overmars and O. Schwarzkopf. 2000. "Computational Geometry:
Algorithms and Applications, Second Edition". Springer-Verlag. Or, Joseph
O'Rourke's 1998 "Computational Geometry in C, Second Edition" published by
Cambridge University Press.

  The latter book's chapter on convex hulls in three dimensions and the one
on search and intersection may give you the tools you need.

Rich

-- 
Dr. Richard B. Shepard, President
Applied Ecosystem Services, Inc. (TM)
<http://www.appl-ecosys.com>