Margus Ramst wrote:
> The 'Box Method':
> With the exception of scanning objects with only 90 degree edges, you would
> always have to do the triangle-culling pass. Otherwise you will not just have
> redundant triangles, but these triangles will intersect - can be very
> conspicuous.

Hmm, yes, especially if we end up with coincidents... something
else I hadn't considered, but I've just been made aware of by my
preliminary box tests. Even with a well chosen discrepency 
threshold for culling, though, there will be some minor overlap 
at the edges that will not be trimmed, so it looks like box
method may well be impractical from what I've seen so far.

> The spherical methods:
> These have the main disadvantage of a very non-uniform distribution of points
> from the poles to the equator, and at different distances from the axis. So, you
> must at least provide, with both methods, for transforming the sampling axis to
> suit an object's geometry.
> A partially improved solution might be an equal-area distribution of samples (on
> the sphere), but I don't have the math skills to help you there.

(looks sheepish) well, that's kind of my fault for illustrating it
the way I did. Actually, I was thinking of beginning with a point 
at the pole and vrotating the rest into place before the scan, so
it would be an even distribution along the arc - it just doesn't
look that way in my illustration due to the fact that I made the
bad choice to use spherical mapping in the illustration which gave
a false impression of the distribution.

Actually, I'm about to start this phase of testing now, and I've
just finished reading up on Justin Whitton's original shield macro
and although he's converted to a proximity pattern, his original
technique of painting triangles over the surface of a complex object
caught my eye for obvious reasons. From what I gathered in his
code, although his objective was quite different in a couple ways
he seems to have used a variation of the spherical scan method 
himself, and got good coverage, so I'm definitely thinking this 
is the most promising approach, hence the acceleration of the 
experiment on that method.
 
> I see no need for the 'progressive intersection' method. My sampling macro
> simply does a new trace from the current intersection point, in the same
> direction as before. It continues doing so until no more intersections are
> found. Thus, you always get all intersections along the current sampling ray.

Actually, someone else (I think it was Ron Parker) mentioned this
before. I was, until this evening laboring under a fundamental
misconception about surface normals that led me to think this would
invert some of the triangle's normals, but as it turned out, this
was based on an untested assumption of mine that I just now proved 
a falsehood, so I appreciate you bringing this up again, as I now 
think this will form an integral part of the final technique.
 
> OK, enough rambling for one night, methinks...

Heh heh. Thanks, I appreciate the rambling, though. It will
be quite helpful. :)

Charles

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