Capítulo 8. SFCGAL Functions Reference
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Capítulo 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.

Las instrucciones de instalación de la biblioteca se pueden encontrar en la página principal de SFCGAL http://www.sfcgal.org. Para cargar las funciones crear la extensión postgis_sfcgal.

8.1. SFCGAL Management Functions

Resumen

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

Resumen

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 geometry. Closed surfaces can have non-zero volume.

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
CG_3DDifference — Perform 3D difference
CG_Distance — Computes the minimum distance between two geometries
CG_3DDistance — Computes the minimum 3D distance between two geometries
CG_3DConvexHull — Computes the 3D convex hull of a geometry.
CG_3DIntersection — Perform 3D intersection
CG_Union — Computes the union of two geometries
CG_3DUnion — Perform 3D union using postgis_sfcgal.
CG_AlphaShape — Computes an Alpha-shape enclosing a geometry
CG_ApproxConvexPartition — Computes approximal convex partition of the polygon geometry
CG_ApproximateMedialAxis — Compute the approximate medial axis of an areal geometry.
CG_GenerateFlatRoof — Generate a flat (box) roof from a footprint polygon.
CG_GenerateHippedRoof — Generate a hipped roof from a footprint polygon.
CG_GenerateGableRoof — Generate a gable roof from a footprint polygon.
CG_GenerateSkillionRoof — Generate a skillion (single-slope) roof from a footprint polygon.
CG_GenerateRoof — Generate a roof of the requested type from a footprint polygon.
CG_PolygonRepair — Repair an invalid polygon or multipolygon.
CG_ConstrainedDelaunayTriangles — Return a constrained Delaunay triangulation around the given input geometry.
CG_Extrude — Extrude a surface to a related volume
CG_ExtrudeStraightSkeleton — Straight Skeleton Extrusion
CG_GreeneApproxConvexPartition — Computes approximal convex partition of the polygon geometry
CG_MinkowskiSum — Performs Minkowski sum
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
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
CG_StraightSkeletonPartition — Computes the straight skeleton partition of a polygon.
CG_3DBuffer — Computes a 3D buffer around a geometry.
CG_Rotate — Rotates a geometry by a given angle around the origin (0,0).
CG_2DRotate — Rotates a geometry by a given angle around a specified point in 2D.
CG_3DRotate — Rotates a geometry in 3D space around an axis vector.
CG_RotateX — Rotates a geometry around the X-axis by a given angle.
CG_RotateY — Rotates a geometry around the Y-axis by a given angle.
CG_RotateZ — Rotates a geometry around the Z-axis by a given angle.
CG_Scale — Scales a geometry uniformly in all dimensions by a given factor.
CG_3DScale — Scales a geometry by separate factors along X, Y, and Z axes.
CG_3DScaleAroundCenter — Scales a geometry in 3D space around a specified center point.
CG_Translate — Translates (moves) a geometry by given offsets in 2D space.
CG_3DTranslate — Translates (moves) a geometry by given offsets in 3D space.
CG_Simplify — Reduces the complexity of a geometry while preserving essential features and Z/M values.
CG_3DAlphaWrapping — Computes a 3D Alpha-wrapping strictly enclosing a geometry.
CG_NurbsCurveInterpolate — Creates an interpolating NURBS curve passing through all given data points
CG_NurbsCurveApproximate — Creates an approximating NURBS curve fitting data points within a tolerance
CG_NurbsCurveDerivative — Computes the derivative (tangent, curvature) of a NURBS curve at a given parameter

8.4. Deprecated SFCGAL Function Aliases

ST_3DIntersection — Deprecated alias for CG_3DIntersection.
ST_3DDifference — Deprecated alias for CG_3DDifference.
ST_3DUnion — Deprecated alias for CG_3DUnion.
ST_Tesselate — Deprecated alias for CG_Tesselate.
ST_3DArea — Deprecated alias for CG_3DArea.
ST_Extrude — Deprecated alias for CG_Extrude.
ST_ForceLHR — Deprecated alias for CG_ForceLHR.
ST_Orientation — Deprecated alias for CG_Orientation.
ST_MinkowskiSum — Deprecated alias for CG_MinkowskiSum.
ST_StraightSkeleton — Deprecated alias for CG_StraightSkeleton.
ST_ApproximateMedialAxis — Deprecated alias for CG_ApproximateMedialAxis.
ST_IsPlanar — Deprecated alias for CG_IsPlanar.
ST_Volume — Deprecated alias for CG_Volume.
ST_MakeSolid — Deprecated alias for CG_MakeSolid.
ST_IsSolid — Deprecated alias for CG_IsSolid.
ST_ConstrainedDelaunayTriangles — Deprecated alias for CG_ConstrainedDelaunayTriangles.
ST_3DConvexHull — Deprecated alias for CG_3DConvexHull.
ST_AlphaShape — Deprecated alias for CG_AlphaShape.
ST_OptimalAlphaShape — Deprecated alias for CG_OptimalAlphaShape.

These ST_ names remain available for compatibility and emit deprecation notices. Their entries contain only the legacy signature and migration link. Use the corresponding CG_ pages for behavior, examples, and geometry support details.

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