Micha Riser <mri### [at] gmxnet> wrote:

> Kaveh wrote:
> 
> > Suppose I have a perfect cube, which is then distorted. I can define the
> > distortion by giving the coordinates of the corners, the midpoints of
> > the edges, and the centers of the faces. How can I draw this new shape,
> > with smooth faces going through the points?
> > 
> 
> You could use bicubic patches with 1 or 4 patches per side (see section
> 3.4.5). If you use 4 of them you can easily fullfill the point 
> interpolation criterion but you have some freedom left in the control
> points. If you use olny 1 per side it gets difficult to have the patch
> interpolate the midpoints and center points.
> 
> But all the same bicubic patches might be the right thing to chose.

Thanks Micha. Look like 4 patches is the right way to go. But a question
here:

- Seems I have to define all pionts, including control points, when the
shapes distort. What I want is to give the changes for the corner
points, which the patch must go through, and let the control points be
chosen automatically so as to create a smooth shape. Is this possible?
If not, how can I calculate those control points?

-- 
Kaveh

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