#version 3.8;
global_settings { assumed_gamma 1 }
#declare Grey50 = srgb <0.5,0.5,0.5>;
background { Grey50 * 0.1 }
#declare Camera00 = camera {
    perspective
    location <3,3,-3.001>*0.75
    sky y
    angle 35
    right x*(image_width/image_height)
    look_at <0,0,0>
}
#declare White = srgb <1,1,1>;
#declare Light00 = light_source { <50,150,-250>, White }
#declare Red = srgb <1,0,0>;
#declare CylinderX = cylinder { -1*x, 1*x, 0.01 pigment { Red } }
#declare Green = srgb <0,1,0>;
#declare CylinderY = cylinder { -1*y, 1*y, 0.01 pigment { Green } }
#declare Blue = srgb <0,0,1>;
#declare CylinderZ = cylinder { -1*z, 1*z, 0.01 pigment { Blue } }

#declare Sphere00 = sphere { 0, 1 }
#declare Disc00   = disc {
    0, y, 0.15, 0.05
    texture          { pigment { Red } }
    interior_texture { pigment { Blue } }
}
#declare Polygon00 = polygon {
    10,
    <-0.15, -0.15>, <-0.15, +0.15>, <+0.15, +0.15>,
    <+0.15, -0.15>, <-0.15, -0.15>
    <-0.05, -0.05>, <-0.05, +0.05>, <+0.05, +0.05>,
    <+0.05, -0.05>, <-0.05, -0.05>
    texture          { pigment { Red } }
    interior_texture { pigment { Blue } }
    rotate x*+90
}
#declare IntrDisc00  = intersection {
    object {Disc00         translate y*0.5}
    object {Sphere00}
}
#declare IntrDisc01  = intersection {
    object {Disc00 inverse translate y*0.5}
    object {Sphere00}
}
#declare IntrDisc01a = intersection {
    object {Disc00         translate y*0.99}
    object {Sphere00}
}
#declare IntrDisc02  = intersection {
    object {Disc00         translate y*1.00}
    object {Sphere00}
}
#declare IntrDisc03  = intersection {
    object {Disc00         translate y*1.1}
    object {Sphere00}
}
#declare IntrPgon00  = intersection {
    object {Polygon00      translate y*0.5}
    object {Sphere00}
}
#declare IntrPgon01  = intersection {
    object {Polygon00 inverse translate y*0.5}
    object {Sphere00}
}
#declare IntrPgon01a  = intersection {
    object {Polygon00         translate y*0.99}
    object {Sphere00}
}
#declare IntrPgon02  = intersection {
    object {Polygon00         translate y*1.00}
    object {Sphere00}
}
#declare IntrPgon03  = intersection {
    object {Polygon00         translate y*1.1}
    object {Sphere00}
}

//--- scene ---
    camera { Camera00 }
    light_source { Light00 }
    object { CylinderX }
    object { CylinderY }
    object { CylinderZ }
  //object { Sphere00 }    // Reference
  //object { Disc00 }      // Reference
  //object { Polygon00 }   // Reference
    #if (frame_number =  1) object { IntrDisc00 } #end  // Fails
    #if (frame_number =  2) object { IntrDisc01 } #end  // Works
    #if (frame_number =  3) object { IntrDisc01a} #end  // Fails
    #if (frame_number =  4) object { IntrDisc02 } #end  // Fails
    #if (frame_number =  5) object { IntrDisc03 } #end  // Works
    #if (frame_number =  6) object { IntrPgon00 } #end  // Works
    #if (frame_number =  7) object { IntrPgon01 } #end  // Works
    #if (frame_number =  8) object { IntrPgon01a} #end  // Works
    #if (frame_number =  9) object { IntrPgon02 } #end  // Works
    #if (frame_number = 10) object { IntrPgon03 } #end  // Works