tesselation

tesselation

Post by me » Sat, 25 Dec 1999 04:00:00



hi and merry X'mas!!!

a little question:
I've made a OpenGL program that use the tesselation, and under Linux-Mesa
all is okay (well, the algorithm is to be reviewed, but it's quite
okay)...

is it possible that isn't there a Windows driver that support OpenGL
tesselation ??? Maybe I haven't found, but otherwise it's very very
strange...


thanks,
   phi

 
 
 

1. wanted: triangular sphere tesselation, n tri-strips ...

... with all the triangle the same size.

I'm trying to write a replacement for OpenGL's gluSphere routine that
does a more reasonable approximation of the sphere.  The glu routine
subdivides evenly among the angles in the two rotational directions,
creating a triangle strip at the top and bottom, and quads wrapping
around.   The problem is that the surface area of the various parts is
not constant, and the top and bottom is degenerate.

So now I'm looking at Jon Leech's code to generate a triangle mesh
approximating a sphere by recursive subdivision. For the first
approximation, he uses an octahedron; each level of refinement
increases the number of triangles by a factor of 4.

This approach can be used to generate a polyganized sphere that is
better because the surface area of the polygons (triangles) would be
the same for all polygons.  The whole thing can be rendered using a
set of triangle strips. If you want the default OpenGL behaviour for
textured spheres, you would replace the top and bottom tri-strips with
a list of triangles so the uv coordinates could be specified properly.

The problem with the code I'm looking at is it uses recursive
subdivision, and therefore does not generate the triangles in the
correct order for triangle strips to be used.   I imagine with some
bookkeeping or an interative algorithm it would be pretty easy to
generate the strips. I want to check if anyone has done it before I
bother.

So, has anyone written the code for such a triangulator?  

--

smail: Dept. of Computer Science, 1214 Amsterdam Ave, Mail Code 0401
       Columbia University, New York, NY 10027-7003

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