Hello all,

            as a newbie I'm very proud of this but that's probably nothing
new for most of you. I animated a set of besier patches so it'd look like
it's breathing. I did it all in the editor in an effort to understand the
maths in it. There's nine patches because I wanted to program something :
first time ever, besides the VCR. Now I like the rhythm and the amplitude,
the shadows and all and I'm ready to pass to other things.
            I would like to learn how to avoid to have the corners of the
individual patches so pointy.
            I do not have any in depth knowledge of the maths of Bezier
curves except for what's a point where the curve actually passes and what's
just a control point. All I know is intuitive, learned by playing with the
code. So I really need your help to go any further.

            The file, even zipped is quite big (1.7 Mb) so I didn't post it
but uploaded it to a site, this one:
  http://pages.infinit.net/copeau/mer001.AVI . The .pov is at
http://pages.infinit.net/copeau/Patch2.pov

            Thanks

            Jean.

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Greetings, Jean!

You might consider posting the pov file in either of the scene-file
groups. In povray.binaries.scene-files if zipped or in
povray.text.scene-files if you just paste it into your message. If you
have already done so, please excuse me. I am on a slow modem
connection and haven't yet d/led the rest of the groups.

Meanwhile I'm off to your site to get the .pov .

Have fun tracing.

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

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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

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


        Nope, Peter,

            on the contrary, this is totally clear.

                Thanks a whole bunch.

                    JM

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Peter Popov wrote:
>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.

And there is more in the povray.advanced-users. Look for the thread
"Q:smooth union of bezier patches" started by ingo.
-- 
...coffee?...yes please! extra sugar,extra cream...Thank you.

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