From: Peter Vanroose <peter_vanroose@ya...>  20051012 15:58:22

> vgl has an elegant alogithm that computes the point on the conic > closest to a given point. > Anyone knows of a reference to that (paper/book)? As the insource documentation states, this is standard plane projective geometry: "The nearest point must have a polar line which is orthogonal to its connection line with the given point; all points with this property form a conic." You can find theory and applications of polar points and lines in any text book on projective geometry. The actual implementation in vgl was not borrowed from any such text book: I just implemented it based on the ideas of polar line/point, and using the algorithm to intersect two conics. (By the way, that intersection algorithm is also a straightforward consequence of standard projective geometry, viz. bundles of conics.)  Peter. 