3D sphere tangent to four triangles

[Ray Jones]

I'm looking for a discussion (or decipherable code) for finding the
set of spheres tangent to four triangles.  

I imagine the straightforward way to do this is to iterate over the
corners (points), edges (lines), and interior (plane) and find a
sphere tangent to four such elements, one from each triangle.  But I
haven't found a description of the solution to this subproblem,
either.

Ray Jones

-------------
The compgeom mailing lists: see
http://netlib.bell-labs.com/netlib/compgeom/readme.html
or send mail to compgeom-request at research.bell-labs.com with the line:
send readme
Now archived at http://www.uiuc.edu/~sariel/CG/compgeom/maillist.html.