In article <3c792e92@news.povray.org>, war### [at] tagpovrayorg says...

> The only concern I have about it is that it uses the "trick" to calculate
> the normal of the spline with the Spline(T+Epsilon)-Spline(T-Epsilon)
> formula. What I'm not sure about is the value for 'Epsilon'.

Why not make it dependent on the distance between the previous and the 
next control point? 
If it is small (1/100 or so) compared to this distance it should work, no 
matter what the absolute scale of the whole thing is.

Has the mesh-approach any advantage over using bicubic patches? The 
documentation says bicubic patches are converted to a mesh internally, so 
speed should be equal (but I didn't try yet), but parsing should be 
faster with patches.

Lutz-Peter

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