"Daniel Nilsson" <dan### [at] daniel-nilssoncom> wrote in
news:3ffb270d@news.povray.org: 

> "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.

I too had some thoughts about doing it that way. But I
thought that it would probably not work. So I wouldn't
spend any time modifying my macros in order to try it.

But now that you suggest this too, I will give it a try.

(I was afraid that I had to change the locations of the
corner points so that the shapes became less rectangular.
Now I hope that it is only necessary to move the two
control points in the middle of each edge.)

Thank you for your suggestion.


Tor Olav

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