// create a isosurface object - the equipotential surface
// of a 3D math function f(x, y, z)
#declare fn_X = function(x,y,z) { x*x + y*y - 1 }  // function cylinder around z axis
isosurface {
  function { x*x + y*y - 1 }          // function (can also contain declared functions
  //function { fn_X(x, y, z) }        // alternative declared function
  contained_by { box { -1.2, 1.2 } }  // container shape
  //threshold 0.0                     // optional threshold value for isosurface [0.0]
  accuracy 0.001                      // accuracy of calculation [0.001]
  max_gradient 4                      // maximum gradient the function can have [1.1]
  //evaluate 5, 1.2, 0.95             // evaluate the maximum gradient
  //max_trace 1                       // maybe increase for use in CSG [1]
  //all_intersections                 // alternative to 'max_trace'
  //open                              // remove visible container surface

  
  texture {
            pigment{ color rgb<1,1.0,0.95>*1.1}
            finish { phong 1}
	  } // end texture

  scale 0.5
  rotate<0,45,0>
  translate <0,0.5,0>  
} // end isosurface