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

  function{ f_torus( x,y,z, 0.75, 0.25)  // major radius, minor radius
          }          

  contained_by {box {<-1,-1,-1>*1,<1,1,1>*1}}
  threshold 0.00 
  max_gradient 5
 
  texture{ 
           pigment{ color rgb <0.2,0.45,1.00>} 
           // normal { bumps 0.15 scale 0.015}
           finish { specular 0.2 phong 0.7 reflection 0.1}
         }
  rotate<-40,20,0>
  scale 1.5
  translate< 0,1.1,0>
} // end of isosurface -------------------------------------------------------