Hello.

Please let me make a question about camera normal.

I made a bump_map bitmap.
I expected it works like a convex lens.
convex_lens2.png:
http://blogimg.goo.ne.jp/user_image/7d/7e/7ee74d483f193c32b07f68bd7eeddfa9.png

Then, I put it to camera normal as follows.

--- begin ---
#include "colors.inc"
#version 3.7;

camera {
  angle 35
  location <0,0.8,-6>
  look_at <0,0.8,0>
  sky y

  normal {
    bump_map {
      png "convex_lens2.png"
      gamma 1.0
    }
    translate <-0.5,-0.5,1>

    bump_size -0.2675
  }
}

light_source {
  <-10,20,-10>
  White
  parallel
  point_at <0,0.8,0>
}

sky_sphere {
  pigment { Navy }
}

plane {
  y, 0
  pigment { Wheat }
}

union {
#for (X1,-4,4,0.2)
  cylinder { <X1,0,0>,<X1,2,0>,0.01 }
#end
#for (Y1,0,2,0.2)
  cylinder { <-4,Y1,0>,<4,Y1,0>,0.01 }
#end
  pigment { Black }
  no_shadow
}
--- end ---

Then I got a result:
http://blogimg.goo.ne.jp/user_image/5d/11/2c9910c2fa6628a86263b0aae2e97bb6.png

But why the normal effects different for X and Y axes?
I expected effects for X and Y are symmetrical, like this(red lines):
http://blogimg.goo.ne.jp/user_image/01/7c/8c99488083c8453cd76bdf4a7b4b7f35.png

Advices appreciated. Thank you very much.

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Am 08.01.2012 17:41, schrieb crowbait:

> I made a bump_map bitmap.
> I expected it works like a convex lens.

...

> But why the normal effects different for X and Y axes?

Even though bump_map bitmaps have been around in POV-Ray for quite some 
time, they've always been flawed (unfortunately they're not trivial to 
fix); consequently, bump maps are good for some more or less random 
distortion, but that's about it. I've never examined how the issue 
affects transmitted light, but I guess what you see is the result of it.

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Thank you very much for intelligible comments.
> bump maps are good for some more or less random
> distortion
Like schlieren of lights? Wow, you gave me another
nice idea to try!

Thanks again,

crowbait

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