El Martes, 6 de Mayo de 2008, Frederik Ramm escribió: > That's a problem with renderers and not a problem with the model. > Whether an area is drawn clockwise or counterclockwise *should* not > make a difference. It is true that you might achive better results *at > the moment* by drawing your areas in a certain direction but it is > certainly not necessary from a data model perspective.
OGC actually takes clockwiseness* into account: "The exterior boundary LinearRing defines the “top” of the surface which is the side of the surface from which the exterior boundary appears to traverse the boundary in a counter clockwise direction. The interior LinearRings will have the opposite orientation, and appear as clockwise when viewed from the “top”, [...] " (See Simple Features Specification, the bit about polygons) A mathematician/topologist would also agree with the fact that a polygon must be counter-clockwise to refer to the "inside" isntead of the "outside". * If "clockwiseness" wasn't a word, I guess that, by now, it is one. > (Unless you want to start discussing that a way loop drawn around a > forest does not exactly specify whether the little bit inside is the > forest or the whole rest of the sphere of the Earth is the forest. > That, indeed, is left open by our way of dealing with things.) It's not left open: it's *defined* by the clockwiseness :-) That old joke about a topologist building a spherical cage and getting "inside" in order to catch a lion comes into my mind... Cheers, -- ---------------------------------- Iván Sánchez Ortega <[EMAIL PROTECTED]> MSN:[EMAIL PROTECTED] Jabber:[EMAIL PROTECTED] ; [EMAIL PROTECTED]
signature.asc
Description: This is a digitally signed message part.
_______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
