Hi everybody. I noticed a strange behaviour when two objects with absorbing
(fade_distance style) interior overlap. Test scene follows.

let's say we have two objects in front of each other, slightly overlapping.
a ray is coming from behind, gets into the first object and is attenuated.
then it enters the second, and it starts interacting with its interior. but
when it gets out of the bounds of the first object, it doesn't interact
with the second one anymore, i.e., if the back object was blue and the
front red, the ray will look blue, not violet.

the problem is really related to the overlap, if I separate the two, the ray
looks violet as it should.

I cannot keep the objects separated, because I want realistic refraction.

Can anybody help? Thanks.

michele

TEST CODE:>>>
global_settings{ max_trace_level 50 }

light_source {
  <-3,10,-10>
  color rgb <1,1,1>
}

light_source {
  <3,-5,4>
  color rgb <1,1,1> *0.5
}

box{
  <0.0,1,-2>,<1,4,2>
  pigment{rgbt 1.0}
  interior{ior 1.00
    fade_distance 0.4
    fade_power 1000
    fade_color <1,0,0>*0.9

  } /* play around with this, moving  the
  box & changing the overlap between the two*/

  translate x*0.1

  translate z*-1
}

box{
  <-1,2,-2>,<0.0,5,2>
pigment{rgbt 1.0}
  interior{ior 1.00
    fade_distance 0.4
    fade_power 1000
    fade_color <0,0,1>*0.9
  }
  translate z*1
}

camera {
  location <7, 5, -0>
  direction 1.0*z
  right     x*image_width/image_height
  look_at   <0.0, 3,  0.0>
}

background { color rgb <1.0,0.8,0.2> }

plane { y ,-0.2
  texture{
    pigment { checker pigment {rgb 1} pigment{rgb <0,0,0.6>} }    finish
{ambient 0.3 diffuse 0.8 }
  }
}

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