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2 Aug 2024 14:19:00 EDT (-0400)
  Reference geometry... (Message 1 to 4 of 4)  
From: Sascha Ledinsky
Subject: Reference geometry...
Date: 22 Oct 2004 17:39:59
Message: <41797e2f@news.povray.org>
I just played a bit with Aqsis and tested something RenderMan calls 
"Reference Geometry".
It's a bit like u/v mapping, but for 3d-textures:
If you've got a mesh that deforms (in an animation), u/v mapping would 
ensure that the texture stayes "attached" to the shape. But 
unfortunately using a 3D procedural texture will not work in POV-Ray, 
the texture would slide around on the geometry.
With RenderMan you can attach the texture to a deforming object in a way 
that the pattern will stick to the surface by defining an (undeformed) 
reference mesh used for texturing.

Theoretically it would be easy to do the same trick with a raytracer:
If you've got the u/v coordinates (e.g. on a bicubic patch or some sort 
of mesh) of the ray intersection, use them to compute the (3d) position 
on the reference patch/mesh and use that for texturing...

The quesition is: Can this be done in SDL?


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From: Tor Olav Kristensen
Subject: Re: Reference geometry...
Date: 22 Oct 2004 18:56:36
Message: <41799024$1@news.povray.org>
Sascha Ledinsky wrote:
> I just played a bit with Aqsis and tested something RenderMan calls 
> "Reference Geometry".
> It's a bit like u/v mapping, but for 3d-textures:
> If you've got a mesh that deforms (in an animation), u/v mapping would 
> ensure that the texture stayes "attached" to the shape. But 
> unfortunately using a 3D procedural texture will not work in POV-Ray, 
> the texture would slide around on the geometry.
> With RenderMan you can attach the texture to a deforming object in a way 
> that the pattern will stick to the surface by defining an (undeformed) 
> reference mesh used for texturing.
> 
> Theoretically it would be easy to do the same trick with a raytracer:
> If you've got the u/v coordinates (e.g. on a bicubic patch or some sort 
> of mesh) of the ray intersection, use them to compute the (3d) position 
> on the reference patch/mesh and use that for texturing...
> 
> The quesition is: Can this be done in SDL?

Yes. There are several techniques described in this thread:

From: ekolis
Subject: Can I bake UV textures with Povray?
Date: 20 Aug 2004 03:05:01

http://news.povray.org/povray.general/thread/%3Cweb.412569f73137e9f1406ebe00%40news.povray.org%3E/
http://tinyurl.com/5l5f4


And here's another message that might be relevant:

From: Slime
Subject: Baking UV textures with POV-Ray
Date: 21 Aug 2004 04:48:25
http://news.povray.org/povray.binaries.scene-files/thread/%3C4126d419@news.povray.org%3E/
http://tinyurl.com/6wrsl

-- 
Tor Olav
http://subcube.net
http://subcube.com


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From: Greg M  Johnson
Subject: Re: Reference geometry...
Date: 22 Oct 2004 22:00:07
Message: <4179bb27$1@news.povray.org>
http://www.geocities.com/pterandon2/alldancecar05d01.html

"Sascha Ledinsky" <sas### [at] userssourceforgenet> wrote in message 
news:41797e2f@news.povray.org...

> But unfortunately using a 3D procedural texture will not work in POV-Ray, 
> the texture would slide around on the geometry.


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From: Sascha Ledinsky
Subject: Re: Reference geometry...
Date: 24 Oct 2004 04:33:24
Message: <417b68d4$1@news.povray.org>
That looks very interesting, thanks!

However I doubt that it will work for bicubic patches. I'll have a look...


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