Re: [Algorithms] Bicubic normals for a bicubic world

[Angel P. <ju...@bi...>]

> 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 )