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- as 50x50x2 = 500 triangles in a mesh2{} shape.
This image is a result from some experiments I
have done recently with functions in POV-Ray
v3.5.
The shape is made by a call to 2 macros:
One macro that builds NURBS functions and one
that takes 3 such functions as parameters and
generates a mesh from them.
This is how these macros; ParametricMesh() and
NURBS_Surface_Fn() can be called in order to
make this shape:
object {
ParametricMesh(
NURBS_Surface_Fn(Order, Knots, Points, Weights, x),
NURBS_Surface_Fn(Order, Knots, Points, Weights, y),
NURBS_Surface_Fn(Order, Knots, Points, Weights, z),
<0.01, 0.01>, <2.00, 2.00>, 50*<1, 1>
)
texture { ... }
}
(The Knots, Points and Weights parameters are
arrays containing the vital information for
the NURBS.)
Here are some statistics:
1 GHz Pentium 3:
Parsing time: 9 sec
Rendering time: 4 sec
100 MHz Pentium:
Parsing time: 1 min 40 sec
Rendering time: 1 min 5 sec
Now I'll go and make sure that my macros
REALLY works as they should and try to find
out how to make the macros generate smaller
functions.
Tor Olav
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Attachments:
Download 'b-splines04_02.jpg' (22 KB)
Preview of image 'b-splines04_02.jpg'
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Tor Olav Kristensen wrote:
>
> - as 50x50x2 = 500 triangles in a mesh2{} shape.
And here is one more image that shows
all these triangles.
Tor Olav
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Attachments:
Download 'b-splines04_03.jpg' (91 KB)
Preview of image 'b-splines04_03.jpg'
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Tor Olav Kristensen wrote:
>
> - as 50x50x2 = 500 triangles in a mesh2{} shape.
>...
Ehhmm... Sorry... 50x50x2 = 5000
Tor Olav
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That is very interesting, I cant wait to see the code behind it.
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This is good news!! I'm eager to know more about it!! My friends often talk
about nurbs. I see you're using my idea of the "irregular" meshes again. Are
you still choosing a random way to connect the triangle quads, or does it
depend on curvature? It seems less random on the picture you posted.
Please tell us more! :o)
Regards,
Hugo
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> Now I'll go and make sure that my macros
> REALLY works as they should and try to find
> out how to make the macros generate smaller
> functions
Let us know ASAP when your macros are ready for beta testers. I think some
of us and ready and willing!
Hershel
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Very nice. I have tried a web search to learn more about a NURBS surface,
but have not found any good information. Do you know of any good sites which
discuss these surfaces?
How much control do you have over the positions of the edges of the surface?
-Shay
Tor Olav Kristensen <tor### [at] hotmail com> wrote in message
news:3C966F97.6D011C37@hotmail.com...
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"Shay" <sah### [at] simcopartscom> wrote in message
news:3c975115@news.povray.org...
> Very nice. I have tried a web search to learn more about a NURBS surface,
> but have not found any good information. Do you know of any good sites
which
> discuss these surfaces?
This one is about NURB curves, the basis for the surfaces:
http://devworld.apple.com/dev/techsupport/develop/issue25/schneider.html
Gleb
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Thank you for your comments.
Halbert & Hershel:
Yesterday, today and tomorrow are busy
days at work, so I will probably not be
able to post any NURBS code before the
weekend.
Hugo:
Yes, I think the meshes here ends up
quite similar to your "irregular"
meshes. But I'm not sure yet.
For each UV-square I have two possible
orientations for its 2 triangles. And
the macro checks which of the two
possible diagonals will be in least
conflict with the location of the
surface in the middle of the UV square.
(The same macro were used for the Bezier
patch shape in the image I posted here
some days ago.)
Shay:
I'm sorry that I don't have time to
explain much now, but here are some
links to a few NURBS pages:
http://www.cs.mtu.edu/~shene/COURSES/cs3621/NOTES/notes.html
http://www.cs.wpi.edu/~matt/courses/cs563/talks/nurbs.html
http://www.ipm.sci-nnov.ru/~demidov/VRML/Splines/Intro/Intro.htm
http://mrl.nyu.edu/~dzorin/geommodel-class/lectures.html
(The links at this page points to Postscript files.)
http://www.cl.cam.ac.uk/Teaching/1999/AGraphHCI/SMAG/advgraphnotes.html
Tor Olav
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