Name
CG_PolygonRepair — Repair an invalid polygon or multipolygon.
Synopsis
geometry CG_PolygonRepair(geometry geom, text rule);
Description
Repair an invalid polygon or multipolygon using CGAL's 2D Polygon
Repair algorithm. Returns a MultiPolygon.
The rule parameter controls the repair strategy:
-
EVEN_ODD(default) — areas covered an odd number of times are kept. Available with CGAL 6.0+. -
NON_ZERO— areas with non-zero winding number are kept. Requires CGAL 6.1+. -
UNION— union of all input polygons. Requires CGAL 6.1+. -
INTERSECTION— intersection of all input polygons. Requires CGAL 6.1+.
Availability: 3.7.0 - requires SFCGAL >= 2.3.0 and CGAL >= 6.0.
This method needs SFCGAL backend.
This function supports Polyhedral surfaces.
Examples
Repair a self-intersecting bowtie polygon with the default EVEN_ODD rule.
WITH data AS (
SELECT 'POLYGON((0 0,2 2,2 0,0 2,0 0))'::geometry AS input_polygon
)
SELECT input_polygon AS input_polygon,
CG_PolygonRepair(input_polygon) AS repaired_polygon
FROM data;
POLYGON((0 0,2 2,2 0,0 2,0 0)) | MULTIPOLYGON(((0 0,1 1,0 2,0 0)),((1 1,2 0,2 2,1 1)))
With the UNION rule, all winding area is kept. This rule requires CGAL 6.1 or later.
WITH data AS (
SELECT 'POLYGON((0 0,2 2,2 0,0 2,0 0))'::geometry AS input_polygon
)
SELECT input_polygon AS input_polygon,
CG_PolygonRepair(input_polygon, 'UNION') AS repaired_polygon
FROM data;
POLYGON((0 0,2 2,2 0,0 2,0 0)) | MULTIPOLYGON(((0 0,1 1,0 2,0 0)))