//Surfaces with critical points
//by Adam Coffman                
//June 2006

camera {
    location  <-0.6,0.7,1.35>
    look_at   <0,0, 0>
      }

 #include "colors.inc"
 background{White}
  
  poly { 4 <
    -2,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-1,2,0,0,0,0>
    sturm 
 pigment {
   brick   rgb <0,0,0,0,0>  rgb <0,0,1,0,.6>
   brick_size <50,0.03,50> mortar 0.005     
   translate <2,0.001125,2> 
 }
    bounded_by { cylinder{<0,3,0> <0,-3,0> 0.55 }  }
    clipped_by { bounded_by }
                  
   }
  
  light_source{<0.5,20,0> White} 
 light_source{<-40,0,0.5> White shadowless}
  light_source{<40,0,0.5> White shadowless}
  light_source{<0,0.5,40> White shadowless}