POV-Ray : Newsgroups : povray.general : scaling problem using uv_mapping image_pattern : Re: scaling problem using uv_mapping image_pattern Server Time
3 Aug 2024 14:11:14 EDT (-0400)
  Re: scaling problem using uv_mapping image_pattern  
From: Eric Medlin
Date: 23 Mar 2004 13:52:07
Message: <eric.medlin-1EE335.13520623032004@news.povray.org>
> You are not understanding at all what an image-pattern does!  It does only
> define a pattern of the image in the unit cube.  The pattern (the checker
> pattern makes this easy to see) together with the normal map is part of the
> the surface normal function, and that is then mapped onto the surface (this
> is what the uv-mapping modifier specifies) using uv-mapping, which is a
> 2d-function, rather than specifying 3d-function.  This is exactly like it
> works for every pattern and every other statement using patterns in POV-Ray.
> In fact, it would not make any sense to just pick arbitrary parts of the
> normal statement and use only them for uv-mapping.
> 
> Just imagine what would happen if what you seem to be expecting was the case
> when using pigments.  The image-map would be uv-mapped and a pigment-map
> would not? - This could never work in a predictable manner at all!
> 

OK, I think I get what you are saying now and that does fit what I am 
observing.  So the image pattern is placed in the unit cube then in this 
case acts as a mask to determine which normals go where.  Then this flat 
image of normals is applied to the box.  I was thinking it applied the 
image pattern to the object then masked off the normals.  I got this 
ideal in my head when I read the last part of 6.7.11.20 Image Pattern 
where it talks about using it to create masks.  I just thought the image 
could be uv mapped onto and object and act like a mask for maps.  So my 
new question is how can I use an image as mask to determine where 
different normals will go put will not scale the patterns I am using as 
normals unless I insert scale x.


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