RE: [Algorithms] Bezier Triangle Rendering

[Tom F. <to...@mu...>]

I just use this one for my triangles:


      +
     / \
    /   \
   +-----+
  / \   / \
 /   \ /   \
+-----+-----+

If you turn your tris into imaginary right-angled tris by picking any two
edges as "major" edges, then use coordinates based on those two, then the
vertices are found at exactly the same positions as a square tesselation of
a square patch. You just have to make sure you split the "squares" along the
correct diagonal:

+
|\
| \
+--+
|\ |\
| \| \
+--+--+
|\ |\ |\
| \| \| \
+--+--+--+

(i.e. if you pick the wrong diagonal, you get this monstrosity:)

+
|\
| \
+--+
| /|\
|/ | \
+--+--+
| /| /|\
|/ |/ | \
+--+--+--+



Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Dave Smith [mailto:Dav...@sd...]
> Sent: 16 August 2000 16:07
> To: gda...@li...
> Subject: [Algorithms] Bezier Triangle Rendering
> 
> 
> I can compute points on a Bezier Triangle,
> but I'm having a tough time coming up with
> a good tessellator for it.  Are there any
> references that has a demonstration of this?
> 
> I'm currently looking at fixed subdivision for 
> the quadratic case, but because its not bi-quadratic 
> in the square sense, like bezier patches, it's harder 
> to come up with an easy algo for producing the parameter
> space points.
> 
> Any ideas or pointers would be much appreciated,
> Thanks,
> -DaveS
> 
> ps.
> 
> Conor, that sure was a "wacky" patent. :-P
> 
> 
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