lwgeom_delaunay_triangulation()

LWGEOM* lwgeom_delaunay_triangulation	(	const LWGEOM *	geom,
		double	tolerance,
		int	edgeOnly
	)

Take vertices of a geometry and build a delaunay triangulation on them.

Parameters

geom	the input geometry
tolerance	an optional snapping tolerance for improved robustness
edgeOnly	if non-zero the result will be a MULTILINESTRING, otherwise it'll be a COLLECTION of polygons.

Definition at line 2004 of file liblwgeom/lwgeom_geos.c.

References GEOS2LWGEOM(), lwerror(), LWGEOM2GEOS(), lwgeom_geos_errmsg, lwgeom_geos_error(), lwgeom_get_srid(), lwgeom_has_z(), lwnotice(), and lwtin_from_geos().

Referenced by ST_DelaunayTriangles(), and test_lwgeom_delaunay_triangulation().

                                                                                             {
#if POSTGIS_GEOS_VERSION < 34
        lwerror("lwgeom_delaunay_triangulation: GEOS 3.4 or higher required");
        return NULL;
#else
        GEOSGeometry *g1, *g3;
        LWGEOM *lwgeom_result;

        if (output < 0 || output > 2) {
                lwerror("lwgeom_delaunay_triangulation: invalid output type specified %d", output);
                return NULL;
        }

        initGEOS(lwnotice, lwgeom_geos_error);

        g1 = (GEOSGeometry *)LWGEOM2GEOS(lwgeom_in, 0);
        if ( ! g1 )
        {
                lwerror("lwgeom_delaunay_triangulation: Geometry could not be converted to GEOS: %s", lwgeom_geos_errmsg);
                return NULL;
        }

        /* if output != 1 we want polys */
        g3 = GEOSDelaunayTriangulation(g1, tolerance, output == 1);

        /* Don't need input geometry anymore */
        GEOSGeom_destroy(g1);

        if (g3 == NULL)
        {
                lwerror("GEOSDelaunayTriangulation: %s", lwgeom_geos_errmsg);
                return NULL;
        }

        /* LWDEBUGF(3, "result: %s", GEOSGeomToWKT(g3)); */

        GEOSSetSRID(g3, lwgeom_get_srid(lwgeom_in));

        if (output == 2) {
                lwgeom_result = (LWGEOM *)lwtin_from_geos(g3, lwgeom_has_z(lwgeom_in));
        } else {
                lwgeom_result = GEOS2LWGEOM(g3, lwgeom_has_z(lwgeom_in));
        }

        GEOSGeom_destroy(g3);

        if (lwgeom_result == NULL) {
                if (output != 2) {
                        lwerror("lwgeom_delaunay_triangulation: GEOS2LWGEOM returned null");
                } else {
                        lwerror("lwgeom_delaunay_triangulation: lwtin_from_geos returned null");
                }
                return NULL;
        }

        return lwgeom_result;

#endif /* POSTGIS_GEOS_VERSION < 34 */
}

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