// parametric object
// not yet worked out
parametric {
  function { u*v*sin (15*v) },            // x-axis
  function { v },                         // y-axis
  function { u*v*cos (15*v) }             // z-axis
  <0,0>, <1,1>
  //contained_by { sphere { 0,1 } } // texturing problem, use box instead to see!
  contained_by { box { <-1,-1,-1>, <1,1,1> } }
  // max_gradient 2
  accuracy 0.005        // 0.001 default, lower slower but better
  precompute 15 x,y,z   // precompute [x,y,z] normally gives faster rendering (<=20)

  rotate 180*x
  scale 1
  texture{ pigment{ color rgb<1,1,1> } 
            
         } 
  translate<0,1,0>
}