I'm fairly sure that this has been reported before, but I can't see it mentioned
in the most recent known bugs list. The red box specified last in the following
code will disappear unless either Top_BC or Bottom_BC (or both) is/are commented
out of the final union.

The problem disappears with -UV

#version 3.5;

#local Cam_Dist = 5;
camera {
  orthographic
  location 0
  right x*Cam_Dist * 4/3
  up y*Cam_Dist
  look_at<0,0,1>
}

#declare TopBack_BC =
difference{
  sphere{0,1 scale <2,0.5,1.5>}
  plane{x,0}
}

#declare Top_BC =
difference{
  object{TopBack_BC}
  plane{y,0}
}

#declare Bottom_BC =
difference{
  object{TopBack_BC scale<1,0.5,1>}
  plane{-y,0}
}

union{
  object{Top_BC} // comment either this or next out to get red box (below)
  object{Bottom_BC}
  pigment{rgb 1}
  finish{ambient 1}
  translate z*4
}

box{0,<1.5,0.25,1.5> translate<0,-0.5,-0.75> pigment{rgb<1,0,0>} finish{ambient
1}}

Post a reply to this message