POV-Ray

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

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

Fixed with changelist 4791

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.

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.

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 }
}