POV-Ray : Newsgroups : povray.general : eval_pigment and uv_mapping? Server Time
3 Aug 2024 16:24:53 EDT (-0400)
  eval_pigment and uv_mapping? (Message 1 to 4 of 4)  
From: Jörg 'Yadgar' Bleimann
Subject: eval_pigment and uv_mapping?
Date: 30 Nov 2003 15:20:34
Message: <3FCA5FC5.B23D7467@gmx.de>
High!

While testing my new "greypat2mesh" macro with various pigment pattern,
I had to notice the eval_pigment obviously doesn't allow the use of
uv_mapping with the pigment to be evaluated - I alway get the error
message "The 'uv_mapping' pattern cannot be used as part of a pigment
function!". Strange... because uv_mapping is rather a pattern modifier
than a pattern itself!

Is there a way to work this around and avoid the ugly distortions when
using a pattern on a sphere without uv_mapping for the mesh calculation?

See you in Khyberspace!

Yadgar


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From: Christoph Hormann
Subject: Re: eval_pigment and uv_mapping?
Date: 30 Nov 2003 16:02:04
Message: <k72q91-6ov.ln1@triton.imagico.de>

> High!
> 
> While testing my new "greypat2mesh" macro with various pigment pattern,

> I had to notice the eval_pigment obviously doesn't allow the use of
> uv_mapping with the pigment to be evaluated - I alway get the error
> message "The 'uv_mapping' pattern cannot be used as part of a pigment
> function!". Strange... because uv_mapping is rather a pattern modifier
> than a pattern itself!

This is not really correct, uv-mapping is a way to map a pattern on an 
object surface.  Naturally eval_pigment() (or pigment/pattern functions 
in general) can't make use of it in any way.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 25 Oct. 2003 _____./\/^>_*_<^\/\.______


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From: Jörg 'Yadgar' Bleimann
Subject: Re: eval_pigment and uv_mapping?
Date: 30 Nov 2003 17:51:27
Message: <3FCA8324.D3FB307B@gmx.de>
High!

Christoph Hormann schrieb:

> This is not really correct, uv-mapping is a way to map a pattern on an
> object surface.  Naturally eval_pigment() (or pigment/pattern functions
> in general) can't make use of it in any way.

What are the underlying (mathematical?) reasons for this behaviour?

See you in Khyberspace!

Yadgar


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From: Christopher James Huff
Subject: Re: eval_pigment and uv_mapping?
Date: 30 Nov 2003 19:36:29
Message: <cjameshuff-6F10EF.19354130112003@netplex.aussie.org>
In article <3FCA8324.D3FB307B@gmx.de>,


> > This is not really correct, uv-mapping is a way to map a pattern on an
> > object surface.  Naturally eval_pigment() (or pigment/pattern functions
> > in general) can't make use of it in any way.
> 
> What are the underlying (mathematical?) reasons for this behaviour?

UV-mapping maps a texture to a surface using the UV coordinates of the 
evaluated point on that surface. Without a surface, there are no UV 
coordinates, and thus no UV mapping. Similarly, the slope pattern only 
works when applied to a surface.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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