//Steiner's Cross-Cap surface
//by Adam Coffman

camera {
    location  <-2.5, 1.5, 1.65>
    look_at   <0, 0, 0>
      }
#include "colors.inc"
  plane { y, 21 pigment{White}}
  box { <4,-3,-1.65> <-6,1.5,-6> pigment{White}}
  plane { y, -1.25
    texture {
      pigment{hexagon}
    }
  }           
  poly { 4 <
  4, 0, 0, 0, 4, 0, 0, 4, 4, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 1, 0, 0, 1, 0, -1, 0, 0, 0, 0, 
  0, 0, 0, 0, 0>sturm pigment{Yellow}    
  bounded_by { box { <-1,-2,-1>, <1,2,1> } }
    clipped_by { bounded_by }           
    }
  poly { 4 <
  4, 0, 0, 0, 4, 0, 0, 4, 4, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 1, 0, 0, 1, 0, -1, 0, 0, 0, 0, 
  0, 0, 0, 0, 0>sturm pigment{SkyBlue}    
  bounded_by { sphere{<0,0,0> 0.2} }
    clipped_by { bounded_by }   
    translate<-0.9,0.55,0.26>     
  }
poly { 4 <
  4, 0, 0, 0, 4, 0, 0, 4, 4, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 1, 0, 0, 1, 0, -1, 0, 0, 0, 0, 
  0, 0, 0, 0, 0>sturm pigment{White}    
  bounded_by { box { <-1,-2,-1>, <1,2,1> } }
  bounded_by { sphere{<0,0,0.9> 0.25} }
    clipped_by { bounded_by }   
             translate<0.07,0,.65> 
    finish {
        ambient .2
        diffuse .6
        specular .75
        reflection .45
     }
  }               
  light_source{<0,20,0> White} 
  light_source{<-40,0,0> White}
  light_source{<0,0,40> White}