"Tor Olav Kristensen" <tor_olav_kCURLYAhotmail.com> wrote in message
news:3ffa3519@news.povray.org...
>
> They show that the surface might not be completely
> smooth around the "seems" between the patches.
>
> My idea was to have all the 8 control points that
> surrounds each "corner point" to lie in the same
> plane.
>
> It seems that the results are better if the star
> around each of the corner points is regular.
>
> But I now have a growing suspicion that it may not
> be possible use bicubic Bezier patches to make such
> a surface (that is completely smooth).
>
> Does anyone know if I'm right about this ?

I did some work with bicubic patches once and iirc I could get at least
tangent continuity between patches if the control points on both sides of
the edge is in a straight line. I found this mostly by my own
experimentation and have no mathematical proof.
To fix you patches try to make the points A, B and C in the attached image
be in one line (and similar for the other edges). That way your star will
actually become a pentagon.

-- 
Daniel Nilsson

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