POV-Ray : Newsgroups : povray.advanced-users : uv_mapping & image_map on mesh/mesh2 help Server Time
5 Jul 2024 15:24:22 EDT (-0400)
  uv_mapping & image_map on mesh/mesh2 help (Message 1 to 5 of 5)  
From: Woody
Subject: uv_mapping & image_map on mesh/mesh2 help
Date: 13 Aug 2007 22:40:00
Message: <web.46c114e5fb0011dde3b389310@news.povray.org>
I was wondering if someone could help me. I am trying to apply a image_map
with uv_mapping to a mesh or mesh2 object (take your pick, pics and text
available for both).

My question is regarding how I get the image to look like it is glued onto a
surface and then the surface is distorted rather than lookling like two
triangles glued together as in the file below? Is there anyway to do this
without decomposing this into baby meshes (by baby mesh I mean mapping the
same image to say a mesh to say 4rows x 4columns with 32 triangles total
instead of one a 1row x 1col mesh w only 2 triangles)? Is there some syntax
to correct for this?


The source is at
http://www.geocities.com/jeffwood581981/mesh.txt
http://www.geocities.com/jeffwood581981/mesh2.txt

The rendered pics are at
http://www.geocities.com/jeffwood581981/mesh.bmp
http://www.geocities.com/jeffwood581981/mesh2.bmp
http://www.geocities.com/jeffwood581981/uvmap.bmp

If it helps the pictue located at
http://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Perspective_correct_texture_mapping.jpg/400px-Perspective_corr
ect_texture_mapping.jpg
seems to address this problem.

The center pic seems to match my files above. I'm trying to achieve the
effect on the right.


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From: Woody
Subject: Re: uv_mapping & image_map on mesh/mesh2 help
Date: 14 Aug 2007 07:55:01
Message: <web.46c1976184cb8d3594e61a50@news.povray.org>
Sorry. Wasn't aware of the geocities data transfer limit.
Pics in gif format can be seen at

http://www.geocities.com/jeffwood581981/mesh.gif
http://www.geocities.com/jeffwood581981/mesh2.gif

Anyone know of any sites where I wouldn't have this problem?


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From: Woody
Subject: Re: uv_mapping & image_map on mesh/mesh2 help
Date: 14 Aug 2007 11:20:00
Message: <web.46c1c7f884cb8d3594e61a50@news.povray.org>
Gif versions located at

http://www.geocities.com/jeffwood581981/mesh.gif
http://www.geocities.com/jeffwood581981/mesh2.gif

Any help greatly appreciated


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From: Tim Attwood
Subject: Re: uv_mapping & image_map on mesh/mesh2 help
Date: 14 Aug 2007 19:48:28
Message: <46c23f4c@news.povray.org>
A mesh consists of triangles (at least in POV).
The uv mapping for each individual triangle
is correct.

However, the perspective effect that you wanted
comes from a quad.

POV supports quads as polygons, but not the
uv mapping for them. That leaves the
bicubic_patch, that can do what you want at
the expense of memory use and render time,
but it requires control points to deal with the
curves. So the most practical solution is just
to subdivide your triangles to get better
uv mapping.


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From: honnza
Subject: Re: uv_mapping & image_map on mesh/mesh2 help
Date: 8 Oct 2007 13:25:01
Message: <web.470a677784cb8d35a9ce4df50@news.povray.org>
"Tim Attwood" <tim### [at] comcastnet> wrote:
> A mesh consists of triangles (at least in POV).
> The uv mapping for each individual triangle
> is correct.
>
> However, the perspective effect that you wanted
> comes from a quad.
>
> POV supports quads as polygons, but not the
> uv mapping for them. That leaves the
> bicubic_patch, that can do what you want at
> the expense of memory use and render time,
> but it requires control points to deal with the
> curves. So the most practical solution is just
> to subdivide your triangles to get better
> uv mapping.

This rendering is the correct one for a set of two triangles at angle.
However, I guess you don't want it to look like a set of two triangles at
angle but as a 3D surface. To do this you need a mesh that doesn't describe
a set of triangles at angle. I'm sorry but this is it.


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