I am using the polar form of the ellipse given at: http://en.wikipedia.org/wiki/Ellipse#Polar_form_relative_to_center
with theta the angle of the point we are checking. (Those cos and sin calculations are easy, just delta-x/len and delta-y/len.) With that I can calculate the distance from the point to an ellipse. Restricting this to an ellipse /segment/ is tricky, since as DJ pointed out, these are not "real" elliptical arcs, but stretched arcs, so the limiting angles do not correspond directly to actual angles. Adding explicit checks for distance from endpoints would give us an almost-correct solution. There are still pathologies I can think of with arcs whose thickness (or thickness + search radius) is greater than the minor axis, though.. -- Andrew Poelstra Email: asp11 at sfu.ca OR apoelstra at wpsoftware.net Web: http://www.wpsoftware.net/andrew/ _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user