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

  function{
   f_rounded_box( x, y, z,
                  0.3, //  radius of curvature
                  1.4,0.9,0.9) // scale<x,y,z>
     -(f_agate(x/2,y/4,z/4)*0.35)
                               
   }

  threshold 0
  contained_by {box {<-2,-1,-1>*1.2,<2,1,1>*1.5}}
  max_gradient 3.2
  accuracy 0.0001

  texture { pigment{ color rgb<1,0.75,0.55>*0.7}
            normal { bumps 0.5 scale 0.05}
            finish { phong 0.3}
	  }
  scale 0.900
  rotate <0,0,0>
  rotate <-20,0,0>  
  translate < 0, 1.3, 0>
} // end of isosurface ------------------------------