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 08:10:56 EDT (-0400)
  Re: scaling problem using uv_mapping image_pattern  
From: Eric Medlin
Date: 23 Mar 2004 09:33:19
Message: <eric.medlin-8CEC8E.09331923032004@news.povray.org>
> I think you are confused about what uv-mapping does and what not.  Please
> read section "6.7.7 UV Mapping" of the manual.  As you do not provide a full
> scene, nobody cannot help you better because the uv-mapping depends on the
> object type as described in the manual.  The image-pattern is always one by
> one (by one) unit in space, while your uv-vectors may very well be
> different.  Without a small but complete scene or at least knowing the
> object type, one cannot help you!
> 
> Another thing I don't really understand is why you are using a JPEG
> image-pattern ... it does not make much sense to use a JPEG for this at all.
> 
>     Thorsten
> 
> ____________________________________________________
> Thorsten Froehlich, Duisburg, Germany
> e-mail: tho### [at] trfde
> 
> Visit POV-Ray on the web: http://mac.povray.org

My understanding is uv mapping allows you to map vertex coord. to points 
on a texture.  I have used them before in opengl, povray, and different 
modeling programs.  A full sample scene is provide below.  By removing 
the uv_mapping you will see the scale changes.  I don't think it should 
though because the patterns used for the normal maps are a function of 
the 3d space they are in and that does not change.  The only think that 
changes is the mapping for the image_pattern that tells which normal map 
to apply where.  You will need to make a simple mask.tga file for the 
image pattern.  I didn't have any reason to use a jpeg.  I just used it.  
Why is it a bad choice?  Compress artifacts?  Anyway here is a sample 
scene that shows my problem.

light_source {
   <5, 5, -5>, rgb <1, 1, 1>
}

global_settings {
   assumed_gamma 1.5
}

camera {
   perspective
   location <0, 0, -1>
   sky <0, 1, 0>
   direction <0, 0, 1>
   right <1.3333, 0, 0>
   up <0, 1, 0>
   look_at <0, 0, 0>
}

box {
   <-0.5, -0.5, -0.5>, <0.5, 0.5, 0.5>
   
   texture {
      normal {
         uv_mapping image_pattern{tga "mask.tga"}
         //image_pattern{tga "mask.tga"}   
         turbulence <0, 0, 0>
         
         normal_map {
            [ 0.5 bozo
            scale 0.02
            ]
            [ 0.5 quilted
            scale 0.02
            ]
         }
      }
      
      pigment {
         color rgb <1, 1, 1>
      }
   }
   scale 1
   rotate <0, 0, 0>
   translate <0, 0.5, 0.5>
}

box {
   <-0.5, -0.5, -0.5>, <0.5, 0.5, 0.5>
   
   texture {
      normal {
         bozo
         scale 0.02
      }
      
      pigment {
         color rgb <1, 1, 1>
      }
   }
   scale 1
   rotate <0, 0, 0>
   translate <0, -0.5, 0.5>
}


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