RE: [Algorithms] Bicubic normals for a bicubic world

[Akbar A. <sye...@ea...>]

hello john,
expensive?

calculate the tangent vectors, compute cross products at each corner of
patch.

lamens;
calculate normals to the parametric surface at the patch corners and assign
these values to the relevant surfaces

>interpolation doesn't help much
you where probably just assigning the plane normals to the triangles,
instead of doing the method above. this should improve your results.

doesn't dx8 have some high level code that does this ??

watt and watt, "advanced animation and rendering techniques"
has a wonderful section on this topic.
page 83

hope this helps, if you need more details please ask.

peace.
akbar A.

"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.


-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of John
Sensebe
Sent: Thursday, August 03, 2000 7:02 PM
To: gda...@li...
Subject: [Algorithms] Bicubic normals for a bicubic world


Hi! I'm new to this list, but already I'm asking questions... ;-)

Does anyone here know how I can approximate the normals across a bicubic
surface (i.e.: a Bezier patch) using another bicubic? I want to use normals
for backface removal, and a simpler interpolation doesn't help much. On the
other hand, an exact biquintic solution would be too expensive to compute.

Thanks.

John Sensebe
jse...@ho...
Quantum mechanics is God's way of ensuring that we never really know what's
going on.

Check out http://members.home.com/jsensebe to see prophecies for the coming
Millennium!




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