isosurface { //-------------------------------------------------------------
  function { (1+0.002)
              - pow( 0.002, ( sqrt(x*x+y*y)-0.5 ) )
              - pow( 0.008, ( abs(x)+abs(z)-0.5 ) )
              - pow( 0.002,( sqrt( y*y+z*z )-0.5 ) )
         //  - f_noise3d( x*3, y*3, z*3 ) 
  }
  contained_by { box { -1.5, 1.5 } }
  accuracy 0.003
  max_gradient 5

  texture{ pigment{ color rgb<1,0.7,0>}
           finish { phong 1}}
  rotate<-30,20,0>
  translate <-0.25, 1.4, 0.5>
} // end of isosurface -----------------------------------------------------