Chapter 8. SFCGAL Functions Reference
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Chapter 8. SFCGAL Functions Reference

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SFCGAL is a C++ wrapper library around CGAL that provides advanced 2D and 3D spatial functions. For robustness, geometry coordinates have an exact rational number representation.

Installation instructions for the library can be found on the SFCGAL home page (http://www.sfcgal.org). To enable the functions use create extension postgis_sfcgal.

8.1. SFCGAL Management Functions

Abstract

This section lists functions for determining version of SFCGAL and library dependencies you are running.

postgis_sfcgal_version — Returns the version of SFCGAL in use
postgis_sfcgal_full_version — Returns the full version of SFCGAL in use including CGAL and Boost versions

8.2. SFCGAL Accessors and Setters

Abstract

These functions access or set properties of geometries. Geometries primarily supported by these functions are TINS and Polyhedral Surfaces.

CG_ForceLHR — Force LHR orientation
CG_IsPlanar — Check if a surface is or not planar
CG_IsSolid — Test if the geometry is a solid. No validity check is performed.
CG_MakeSolid — Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
CG_Orientation — Determine surface orientation
CG_Area — Calculates the area of a geometry
CG_3DArea — Computes area of 3D surface geometries. Will return 0 for solids.
CG_Volume — Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
ST_ForceLHR — Force LHR orientation
ST_IsPlanar — Check if a surface is or not planar
ST_IsSolid — Test if the geometry is a solid. No validity check is performed.
ST_MakeSolid — Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
ST_Orientation — Determine surface orientation
ST_3DArea — Computes area of 3D surface geometries. Will return 0 for solids.
ST_Volume — Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.

8.3. SFCGAL Processing and Relationship Functions

CG_Intersection — Computes the intersection of two geometries
CG_Intersects — Tests if two geometries intersect (they have at least one point in common)
CG_3DIntersects — Tests if two 3D geometries intersect
CG_Difference — Computes the geometric difference between two geometries
ST_3DDifference — Perform 3D difference
CG_3DDifference — Perform 3D difference
CG_Distance — Computes the minimum distance between two geometries
CG_3DDistance — Computes the minimum 3D distance between two geometries
ST_3DConvexHull — Computes the 3D convex hull of a geometry.
CG_3DConvexHull — Computes the 3D convex hull of a geometry.
ST_3DIntersection — Perform 3D intersection
CG_3DIntersection — Perform 3D intersection
CG_Union — Computes the union of two geometries
ST_3DUnion — Perform 3D union.
CG_3DUnion — Perform 3D union using postgis_sfcgal.
ST_AlphaShape — Computes an Alpha-shape enclosing a geometry
CG_AlphaShape — Computes an Alpha-shape enclosing a geometry
CG_ApproxConvexPartition — Computes approximal convex partition of the polygon geometry
ST_ApproximateMedialAxis — Compute the approximate medial axis of an areal geometry.
CG_ApproximateMedialAxis — Compute the approximate medial axis of an areal geometry.
ST_ConstrainedDelaunayTriangles — Return a constrained Delaunay triangulation around the given input geometry.
CG_ConstrainedDelaunayTriangles — Return a constrained Delaunay triangulation around the given input geometry.
ST_Extrude — Extrude a surface to a related volume
CG_Extrude — Extrude a surface to a related volume
CG_ExtrudeStraightSkeleton — Straight Skeleton Extrusion
CG_GreeneApproxConvexPartition — Computes approximal convex partition of the polygon geometry
ST_MinkowskiSum — Performs Minkowski sum
CG_MinkowskiSum — Performs Minkowski sum
ST_OptimalAlphaShape — Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.
CG_OptimalAlphaShape — Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.
CG_OptimalConvexPartition — Computes an optimal convex partition of the polygon geometry
CG_StraightSkeleton — Compute a straight skeleton from a geometry
ST_StraightSkeleton — Compute a straight skeleton from a geometry
ST_Tesselate — Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
CG_Tesselate — Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
CG_Triangulate — Triangulates a polygonal geometry
CG_Visibility — Compute a visibility polygon from a point or a segment in a polygon geometry
CG_YMonotonePartition — Computes y-monotone partition of the polygon geometry

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