#default{pigment{rgb 1}}
camera{location 5*<0,1,-1> look_at 0 angle 30}
light_source{ 5*<1,1,-1> rgb 1}
prism {
linear_spline -0.5 0.5 4
<-1,-1><1,0><-1,1><-1,-1>
//sturm
}
I rendered it with an i-Mac and a Power G3 and the results were the same.
It seems to me that there is a problem with the normals.