Hi,

I want to use POV-Ray to simulate an physicalic correct x-ray image. To do that
I use completely transparent bodies (filter 1) and the physicalic correct fade
distance for the used materials. To test this, I create two boxes on top of each
other. The code looks like this (don't
wonder about the small values, I need to work with millimeters):

//----------------------------
#include "colors.inc"
#declare Nothing = texture {pigment {color White filter 1} }
#declare Metall1 = interior{ fade_power 1000  fade_distance 8.8865E-5}
#declare Metall2 = interior{ fade_power 1000  fade_distance 3.01368E-4}

light_source { <0,0,0.1> color rgb <1,1,1> }
camera {orthographic location <0,0,-0.1> look_at <0,0,0> angle 5 }
background { color White }


box { <-2E-3, -0.5E-3, 0>, <2E-3, 0.5E-3, 0.03E-3>
texture {Nothing}
interior {Metall1}
 }


box { <-0.5E-3, -2E-3, 0.03E-3>, <0.5E-3, 2E-3, 0.06E-3>
texture {Nothing}
interior {Metall2}
 }
//----------------------------


When you try this code you will notice, that the boxes are not transparent on
their touching area. If you "push" the upper box a little bit higher so they
don't touch each other any more (1E-6 is enough), then you get the expected and
correct image.


//----------------------------
#include "colors.inc"
#declare Nothing = texture {pigment {color White filter 1} }
#declare Metall1 = interior{ fade_power 1000  fade_distance 8.8865E-5}
#declare Metall2 = interior{ fade_power 1000  fade_distance 3.01368E-4}

light_source { <0,0,0.1> color rgb <1,1,1> }
camera {orthographic location <0,0,-0.1> look_at <0,0,0> angle 5 }
background { color White }


box { <-2E-3, -0.5E-3, 0>, <2E-3, 0.5E-3, 0.03E-3>
texture {Nothing}
interior {Metall1}
 }


box { <-0.5E-3, -2E-3, 0.03E-3+1E-6>, <0.5E-3, 2E-3, 0.06E-3+1E-6>
texture {Nothing}
interior {Metall2}
 }
//----------------------------


Has anybody an idea why this happens and how I can avoid that effect without
"pushing" bodies around?

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