00849nas a2200145   4500000000100000008004100001260004300042100002100085700001700106700001500123700001500138700001700153245007400170520045900244       2007                            d  cXbSpringer VerlagaHeidelber, Germany1 aLeszek Luchowski1 aM. Kurzynski1 aM. Wozniak1 aE. Puchala1 aA. Zolnierek00aStability of feature points defined by approximating quadric surfaces3 aThe analysis of freeform surfaces requires them to be reduced to more regular geometric structures. One approach is to approximate fragments of the given surface by quadrics, then use the points, lines, and planes defined by the quadric as bases for measurements. The present work describes a series of experiments designed to assess the stability of points defined in this way on human facial features. Both positive and negative findings are discussed.