From what I saw you have a group of 3x3 patches that are identical.
You are moving the edge control points down and the inner control
points up. You can achieve that by declaring a single patch and
multiplying it 3x3 times, but this in to the point of your question.

If you want to understand the insides of bicubics math, I recommend
you looked at the povray.newusers group. There is a thread called
"Bicubic Patches" started by Phill Cute. The follow-up post by
Scott.David.Daniels is a really comprehensive explanation of the
subject.

As of your original question, why are the patches so pointy, well,
it's just because it's the way you've defined the control points.
Since, if you want to match two patches seamlessly along an edge, you
have to match their control points on that edge, the total number of
control points on your 3x3 array of patches is actually 10x10 = 100.
The number of points is 10 because column 1 and 2 of your 3x3 matrix
share an edge, as do column 2 and 3, and that applies for rows as
well. I suggest you make an array of 10x10 points and work with them
instead, taking into account the problem with sharing edges.

If this is totally unclear, I will cook up an example.

---------
Peter Popov
ICQ: 15002700

Post a reply to this message