camera{location 1-y} light_source{1-y 1.5 spotlight radius 5point_at 1-y+z} #declare F=function{pigment{agate}} isosurface{function{F(z*4,y*8,x*4).gray-.5} max_gradient 99 pigment{agate scale .01*y} scale 40normal{granite .2scale .0002turbulence 1}}