Steve Baker (steve++at++mred.bgm.link.com)
Wed, 14 Aug 96 16:35:44 -0500
> The only case where you get into trouble is if a decal overflows
> its base because then the base cannot set all of the proper stencil
> bits and the base may hit junk set by previous bases. So, decals
> must lie completely within their base poygons.
...or the base polygon is translucent and using multisample transparency...
in which case there is no guarantee that the base polygon hits all those
teeny-tiny subpixels...
...or the case where the daughter polygon lines up exactly along the edge
of the host - but teeny-tiny roundoff errors cause the decal polygon to hit
a couple of sub-pixels off the edge of the base....
Technically, Sharon is correct in that in both of the cases that I list
above are properly cases where the decal overflowed the base. But in a
practical world of automatically generated or converted databases, I
can't guarantee that these kinds of conditions won't sometimes crop up.
The problem with this trick is that it looks great on paper but fails in
so many practical examples. When it fails, it does not do so gracefully
but peppers your display with thin slivers of screwed up mess. What's worse
is that a surface very close to your eye can get corrupted by some other
polygons twenty miles away behind it.
Steve Baker 817-323-1361 (Vox-Lab)
Hughes Training Inc. 817-695-8776 (Vox-Office/vMail)
2200 Arlington Downs Road 817-695-4028 (Fax)
Arlington, Texas. TX 76005-6171 steve++at++mred.bgm.link.com (eMail)
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