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I'm interested in knowing more about how bicubic patches work, so that I can
maybe make some macros that can extent the things possible to do with
bicubic patches.
Here's a challenge:
Make a macro takes 16 points as input and then creates a mesh similar to the
corresponding bicubic patch.
Oh, well, I probably can't expect that anyone do that just because I ask,
but then I at least hope someone can point me to resources that contains
enough information that I will be able to do it myself.
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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in news:3c66bbb9@news.povray.org Rune wrote:
> Here's a challenge:
>
> Make a macro takes 16 points as input and then creates a mesh similar
> to the corresponding bicubic patch.
Search for bicubic.inc by John VanSickle,
don't remember in what group under what title though,
Ingo
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Rune <run### [at] mobilixnet dk> wrote:
: Make a macro takes 16 points as input and then creates a mesh similar to the
: corresponding bicubic patch.
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.
--
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}// - Warp -
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in news:Xns### [at] povrayorg ingo wrote:
> Search for bicubic.inc by John VanSickle,
> don't remember in what group under what title though,
>
>
Found it:
Message-ID: <3AD772B7.C88CC3B0@erols.com>
From: John VanSickle <van### [at] erolscom>
Newsgroups: povray.binaries.utilities
Subject: Re: Bicubic patch to mesh?
Date: Fri, 13 Apr 2001 23:42:15 +0200
Xref: news.povray.org povray.binaries.utilities:3084
Ingo
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"ingo" wrote:
> Search for bicubic.inc by John VanSickle,
> don't remember in what group under what title though,
Can't find it anywhere, on news.povray.org or with google.
When searching for bezier.inc I get some results, but only to create bezier
lines, not bezier patches, and it's not made by John VanSickle either.
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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Never mind, I think I've just seen the light.
It was on this page:
http://www.gamedev.net/reference/articles/article1584.asp
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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Rune wrote:
> I'm interested in knowing more about how bicubic patches work, so that I can
> maybe make some macros that can extent the things possible to do with
> bicubic patches.
Please see my recent posts in p.t.s-f
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I wrote:
> Never mind, I think I've just seen the light.
>
> It was on this page:
> http://www.gamedev.net/reference/articles/article1584.asp
But still thanks to Ingo and Warp. Now I have both the theory and some
working examples. :)
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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"Dave Dunn" wrote:
> Rune wrote:
>
> > I'm interested in knowing more about how bicubic
> > patches work, so that I can maybe make some macros
> > that can extent the things possible to do with
> > bicubic patches.
>
> Please see my recent posts in p.t.s-f
???
As far as I can see those don't do anything like what I requested.
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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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3c66e67d@news.povray.org...
> "Dave Dunn" wrote:
> >
> > Please see my recent posts in p.t.s-f
>
> As far as I can see those don't do anything like what I requested.
Hmmm, if Dave hadn't pointed his files out I would have. Sounded just ike
the thing you were asking to me too. Creates a bicubic_patch by macro and
places wireframe for it. You going to make a triangle mesh from the patch?
I'd think that would work out by replacing the wireframe with triangles
maybe.
Admittedly, I haven't seen the others mentioned already.
bob h
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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] tagpovrayorg> 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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