RE: [Algorithms] Some N-Patch questions...

[Peter W. <Pet...@vi...>]

> 
> I use each of these midpoints as a new vertex to split the 
> original triangle
> into 4. To calculate the normals at each new vertex, I 
> interpolate halfway
> between the two adjacent original normals, eg
> MidNorm=Cos(45)*Norm0+Sin(45)*Norm1.

I know it's bad form to reply to your own post, but I want to correct the
normal interpolation method I gave above. The formula above only works when
the two normals are perpendicular, in general I think you'll actually need
to add the two normals, and then renormalise the resultant vector to get the
new normal,
eg MidNorm=(Norm0+Norm1) / (|Norm0+Norm1|)

As far as I can see, any desired method can be used to interpolate the
normals, as long as it's deterministic and continuous you'll get some
variety of smooth surface. I'd like to try applying some normal perturbation
stuff like bump-maps to the interpolation code, I think you'd get
interesting effects as the surface tried to match the perturbed normals.

Peter Warden