// Parametric Example Code

camera { 
    location <-2.5,2.5,-2.5> 
    look_at  <0,0,0>
    angle    50
}

light_source { <-3, 10, 3> color rgb 1.0 shadowless }
light_source { <0, -10, 0> color rgb 1.0 shadowless }

sky_sphere {
    pigment {
        color <0,0,1>
    }
}    

#declare Fr = function { 0.2 + 0.2*sin(5*pi*v)};
#declare Fx = function { Fr(u,v,0)*cos(u) };
#declare Fy = function { v };
#declare Fz = function { Fr(u,v,0)*sin(u) };

#declare maxG = 2;

#declare startU = 0;
#declare startV = -1;
#declare endU = 2*pi;
#declare endV = 1;

parametric {
    function { Fx(u,v,0) },
    function { Fy(u,v,0) },
    function { Fz(u,v,0) }
    <startU, startV>, <endU, endV>
    contained_by { box {<-1,-1,-1>,<1,1,1>} }
    max_gradient maxG
    pigment { rgb 0.9 }
    finish { phong 0.5 phong_size 10 }
}