isosurface { //-------------------------------------------------------------

  function {  sqrt(x*x + z*z) - 0.65 }
  
  threshold 0
  contained_by {box {<-1,-1,-1>, < 1, 1, 1>}}
  //open
  texture {
            pigment{ color rgb<0.3,0.7,0.9>}
            finish { specular 0.3 phong 1}
	  }
  scale 1
  rotate <0, 0, 0>
  translate <-0, 1.1, 0>
} // end of isosurface -----------------------------------------------------