A couple of months ago I did some thinking and computations
on bicubic patches. If I remember correctly, you can get
bicubic patches 2nd order continuous in the vertices (or
any two points along the edge), but only zeroth order
along the edges. So, sorry, completely smooth surfaces
can not be made with bicubic pathes in general in this way.

     Andrel


Tor Olav Kristensen wrote:

> "Rune" <run### [at] runevisioncom> wrote in news:3ff973fd@news.povray.org:
> 
> 
>>I have never been able to figure out how to completely smoothly have
>>another number than four bicubic patches meet at a point. What rules did
>>you use to accomplish it?
>>
>>It would be nice if you gave all the patches the same color, and maybe a
>>little phong or specular, so the smoothness can be better examined. From
>>the posted images, it's impossible to tell if the surface really is
>>completely smooth.
> 
> 
> 
> I have rendered some images with specular highlights.
> 
> 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 ?
> 
> Or have anyone seen images that shows the contrary ?
> 
> 
> Tor Olav
> 
>

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