{
	Calculate coordinates for a 180 degree fisheye lens.
	Assume view direction is (0,1,0), view up (0,0,1), (1,0,0) right.

	4/30/90
}

fish_u = .5 + Dx/fish_Rxz * fish_Ry;
fish_v = .5 + Dz/fish_Rxz * fish_Ry;

fish_Rxz = sqrt(Dx*Dx + Dz*Dz);
fish_Ry = acos(Dy) / PI;