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

  function{ 
    y 
    + f_spikes_2d(
      x,y,z,
      2,   // height of central spike,
      12,  // frequency of spikes in the x direction,
      12,  // frequency of spikes in the z direction,
      0.75 // rate at which the spikes reduce as you move away from the center
    )
  }          
  contained_by {box {<-1,0,-1>*2,<1,2,1>*2}}
  threshold 1.55//1.25
  max_gradient 8
 
  texture{ pigment{ color rgb <1,0.15,0.30>} 
           // normal { bumps 0.15 scale 0.015}
           finish { specular 0.2 phong 0.7 reflection 0.2}
         }
  rotate<-40,10,0>
  scale 0.65
  translate< 0,1.1,0>
} // end of isosurface -------------------------------------------------------