Is the following correct? For a given value y, you want two formulae: x = Fx(y) and z = Fz(y) <http://forum.openscad.org/file/t3184/Maths-1.jpg> And it's important that your cone is orientated exactly as you have specified, rather than in some other position that might make the calculations easier? If Yes to both then I expect other functions in BOSL2 could deliver that, in the hands of somone like Adrian. But it should also be possible from first principles and grunt work. -- Sent from: http://forum.openscad.org/