On 11/17/18, Richard Damon <rich...@damon-family.org> wrote: > On 11/17/18 8:37 PM, Graham Hardman wrote: >> >> My question then is, is it really necessary to ensure a counterclockwise >> order when a polygon shape is entered for the first time in the table. >> > My guess would be that SOME operations will need the vertices in the > right order, and others will work regardless of order. >
Yeah. For example, the geopoly_area() routine returns a negative number if the vertexes rotate iCW instead of CCW (which is also a convenient way to figure out of the order is incorrect). I'm not sure what other routines malfunction, but I suspect most of them will. There is a new routine on trunk (and soon to be in 3.26.0) named geopoly_ccw() that puts the vertexes in the correct CCW order if they are not already so. This routine was added because I discovered that many legacy GeoJSON files do not follow the rules and put polygon vertexes in CW order. I suppose it can also be used after geopoly_xform() to make sure that the vertexes are in the correct order there, too. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
