[Short introductory note: I introduced my brother to POV some time ago
and he has a lot of fun with it. Until now, when he discovered something
which could be a POV bug. I post on his behalf here because he isn't
used to newsgroups at all, unlike me.]

The problem is best described with a picture. See my posting in
povray.binary.images with the same subject for the resulting image and
for the png file needed for the image_map (Although any image with some
transparency in it would do). The scene file follows:



// +w320 +h240 +ibug.pov +obug.png +fn

#include "colors.inc"

camera {
  location <-1,1.5,-1.5>
  look_at <0,0.5,0>
}

light_source {
  <5,5,-5>
  color White
}

light_source {
  <-1,1.5,-1.5>
  color White
}

plane {
  y,0
  texture { pigment { color White } } 
}

difference {
  cylinder { <0,0,0>,<0,1,0>,1/3
    texture { pigment { color Red } }
  }
}

cylinder {
  <0,0.1,0>,<0,0.9,0>,1/3+1/10000
  texture {
    pigment {
      image_map {
        png "image.png"
        map_type 2
      }
      scale 0.8
      translate <0,0.1,0>
    }
  }
}



Yes I know, the difference should contain at least 2 elements, but the
difference is actually what makes the difference :-) here. If you
comment out the two lines "difference {" and the matching "}" the scene
renders ok, but with them it does not. Now, what does the warning want
to tell me:

a) that a difference with only 1 object inside might render
wrong under certain circumstances and should therefore be avoided, or
b) that a difference with only 1 object inside is pretty senseless
syntax-wise but otherwise ok.
c) both

What is the intended meaning of the warning? If a) it should be made
more clear in the docs that such things can happen, and what I've
described is no bug but a feature (since it's documented :-)), and if b)
then what I've described is really a bug and should be fixed. The answer
for c) is obvious.

Now, bug or feature? Comments are welcome.

-- 
Timon Christl <me### [at] christltimonde>

"Hungarian Notation is the tactical nuclear weapon of source code
obfuscation techniques" -- Unknown

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