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"bob h" wrote:
> Hmmm, if Dave hadn't pointed his files out I would have.
> Sounded just like the thing you were asking to me too.
> Creates a bicubic_patch by macro and places wireframe for it.
A bicubic patch AKA a bezier patch is a mathematically defined surface that
is used in many other programs than POV-Ray.
I wanted to create a bicubic patch surface using a *mesh*, not using the
build-in bicubic patch object in POV-Ray. This is because I wanted to know
how bicubic patches work at a low level.
That's what I meant and that's what I wrote, but I could have made it more
clear I guess.
Anyway, thanks for your good intentions Dave an Bob!
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Jan 20)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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On Mon, 11 Feb 2002 02:12:26 +0100, Rune wrote:
> I wanted to create a bicubic patch surface using a *mesh*, not using the
> build-in bicubic patch object in POV-Ray. This is because I wanted to know
> how bicubic patches work at a low level.
As you know, one of the methods that already exists for bicubic patches
turns them into meshes, so you could look at the source code for POV
itself to see how this is done.
--
#macro R(L P)sphere{L __}cylinder{L P __}#end#macro P(_1)union{R(z+_ z)R(-z _-z)
R(_-z*3_+z)torus{1__ clipped_by{plane{_ 0}}}translate z+_1}#end#macro S(_)9-(_1-
_)*(_1-_)#end#macro Z(_1 _ __)union{P(_)P(-_)R(y-z-1_)translate.1*_1-y*8pigment{
rgb<S(7)S(5)S(3)>}}#if(_1)Z(_1-__,_,__)#end#end Z(10x*-2,.2)camera{rotate x*90}
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Warp <war### [at] tag povrayorg> wrote:
> Colefax's PCM macros can place objects on the surface of a bicubic
patch.
> Thus it should be rather easy to adapt it to calculate vertex point on the
> surface of the bicubic patch.
Funnily enough, the pcm.mcr file contains a macro called
PCM_get_patch_point, that takes an array of 16 bezier-patch control points
and a U, V coordinate, and returns a point on the patch's surface
accordingly. There's also a macro that will convert the control points into
a grid of surface points of arbitrary resolution, and (of course!) the
source for all these calculations is freely available.
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"Ron Parker" wrote:
> As you know, one of the methods that already exists
> for bicubic patches turns them into meshes
Yes I know.
> so you could look at the source code for POV
> itself to see how this is done.
Not very easy when I don't know C I imagine and for that same reason I don't
have the source code lying around. Is it generally simple enough to learn
from the source code even though you don't know C (or C++ for that matter)?
Anyway, as mentioned, I found some other ways to learn about it.
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Jan 20)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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Take a look at
http://www.spiritone.com/~english/cyclopedia/patches.html
With my experiences here it seems that it uses the 16 control points and
calculates mesh positions along 8 different bezier splines.
Josh English
eng### [at] spiritonecom
http://www.spiritone.com/~english
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