Re: Re: button-hole problem

> The way I do perspective projection implies that the plane of
> projection is always perpendicular to the line from
> `Focus::position' to `Focus::direction', which are both `Points'.

Ah, so if I understand well, you are using parallel projection?
This is indeed a special case of projective projection, where the
"eye" point is far away (strictly speaking: at infinity).



--	Peter.