POV-Ray

The Persistence of Vision Raytracer (POV-Ray).

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Attached to Project: POV-Ray
Opened by Tim Attwood - 2009-05-22
Last edited by Christoph Lipka - 2010-03-26

FS#31 - function pattern in image map

Function use in image maps is broken.

The following should result in a white and green checkered unit square, but is transparent.

camera {
   location  <0.0, 0.5, -4.0>
   direction 1.5*z
   right     x*image_width/image_height
   look_at   <0.0, 0.0,  0.0>
}

background {rgb <1,1,1>}

light_source {
  <-30, 10, -30>           
  color rgb <1, 1, 1> 
}

plane {y,-1 pigment{checker rgb <1,0,0> rgb <1,0.5,0.5> }}

plane {y,-0.99 
 pigment {
  image_map { 
   function 10,10 { 
    pigment {checker rgb <0,1,0>, rgb <1,1,1> scale 0.1}
   }
   once 
  }
  rotate <90,0,0>
 }
}
Closed by  Christoph Lipka
Friday, 26 March 2010, 16:50 GMT
Reason for closing:  Fixed
Additional comments about closing:  

No feedback from beta testers on the originally reported problem for months, so probably "no news is good news"

Admin
Christoph Lipka commented on Sunday, 24 May 2009, 19:13 GMT

Confirmed with current 3.7.0 development version; looks like the effect of the transmit component is inverted.

Admin
Christoph Lipka commented on Sunday, 24 May 2009, 19:37 GMT

For function images, wrong function was called to store image data (Image::SetRGBAValue instead of Image::SetRGBFTValue)

Admin
Christoph Lipka commented on Sunday, 24 May 2009, 19:44 GMT

Fixed with changelist 4791

Grimbert Jérôme commented on Thursday, 23 July 2009, 18:41 GMT

Beta 33, sources, Linux amd64:

Could somebody explains how the suggested scene was ok ?

according to documentation, image_map in pigment expect a file type, a file name (as string) then modifier...

http://wiki.povray.org/content/Documentation:Reference_Section_8.2

That the proposed scene parsed fine... leave 2 options: documentation must be updated (and currently scene does not work), or the parser need to stop that silly script.

Tim Attwood commented on Friday, 24 July 2009, 02:00 GMT

The documentation needs updated.

The syntax for function images is in section 3.5.11.16 "Function Image",
but it probably should be referenced in section 3.5.1.5.1 "Specifying an Image Map".

The same thing for function height_fields in section 3.5.11.16 "Function Image",
they probably should get a sub-section and be referenced in section 3.4.1.5 "Height Field".

Note: the docs in the quickref are correct... in section 3.8.10.8 "Pattern Modifiers"
shows BITMAP_IMAGE is either FUNCTION_IMAGE or BITMAP_TYPE FILE_NAME.

Grimbert Jérôme commented on Thursday, 13 August 2009, 16:00 GMT

The scene works with Beta.33 (linux, 64bits, from sources)
but would really benefit from explicit finish setting.

Notice that due to sampling of checker pattern along the 0 position (is that the real cause), the image of a scaled to 1/10 with 10x10 samples is not a regular checker.
(Hello, shannon anyone ???)

No more a bug, close it and create a task for documentation ?

camera {
   location  <0.0, 0.5, -4.0>
   direction 1.5*z
   right     x*image_width/image_height
   look_at   <0.0, 0.0,  0.0>
}

background {rgb <1,1,1>}

light_source {
  <-30, 10, -30>           
  color rgb <1, 1, 1> 
}

plane {y,-1 pigment{checker rgb <1,0,0> rgb <1,0.5,0.5> }
finish {ambient 0.5 diffuse 0.5 }
}

plane {y,-0.99 
 pigment {
  image_map { 
   function 10,10 { 
    pigment {checker rgb <0,1,0>, rgb <1,1,1> 
    scale 0.1
    }
   }
   once 
  }
  rotate <90,0,0>
 }
 finish { ambient 1 }
}


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