Attempting to vis ad_tears drags a few lurking bugs out of
SmallestEnclosingBall_vf: poor calculation of 2-point affine space, poor
handling of duplicate points and dropped support points, poor
calculation of the new center (related to duplicate points), and
insufficient iterations for large point sets. qfvis (modified for
cluster spheres) now loads ad_tears.
Scaling the checks by 1e-6 was a little too tight for very small
triangles, but 1e-5 seems to work well. This fixes SEB getting stuck for
a ridiculously small (for quake) triangle in ad_tears (probably resulted
from some bad math in qfbsp when generating the portal file from the
bsp).
When I ported SEB to python, I discovered that I apparently didn't
really understand the paper's description of the end condition and the
usage of the affine and convex sets for center testing. This cleans up
the test and makes SEB more correct for the cases that have less than 4
supporting points (especially when there are less than 4 points total).
Now we can get tight (<1e-6 * radius_squared error) bounding spheres. More
importantly (for qfvis, anyway) very quickly: 1.7Mspheres/second for a 5
point cloud on my 2.33GHz Core 2 :)
