Re: [Algorithms] Bicubic normals for a bicubic world

[John S. <jse...@ho...>]

I've experimented with this, but as you've indicated, the closeness of the
approximation hinges on the two approximated (middle) points. If someone
could give me some help determining where those points should be, I'd
certainly appreciate it. ;-)

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

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----- Original Message -----
From: "Angel Popov" <ju...@bi...>
To: <gda...@li...>
Sent: Friday, August 04, 2000 4:19 AM
Subject: Re: [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.
>
> What about creating another patch with control points displaced one unit
> along the normal ( Easy to do with the control points at the corners, but
what
> about the other control points? This is very easy with DX8 N-Patches).
> Then the normal can be computed like this:
> Normal( U,V ) = P2( U,V ) - P1( U,V )
>