Package org.hipparchus.geometry.euclidean.twod.hull

Class MonotoneChain

java.lang.Object
org.hipparchus.geometry.euclidean.twod.hull.MonotoneChain
All Implemented Interfaces:
ConvexHullGenerator2D, ConvexHullGenerator<Euclidean2D,Vector2D>
public class MonotoneChain extends Object
Implements Andrew's monotone chain method to generate the convex hull of a finite set of points in the two-dimensional euclidean space.

The runtime complexity is O(n log n), with n being the number of input points. If the point set is already sorted (by x-coordinate), the runtime complexity is O(n).

The implementation is not sensitive to collinear points on the hull. The parameter includeCollinearPoints allows to control the behavior with regard to collinear points. If true, all points on the boundary of the hull will be added to the hull vertices, otherwise only the extreme points will be present. By default, collinear points are not added as hull vertices.

The tolerance parameter (default: 1e-10) is used as epsilon criteria to determine identical and collinear points.

See Also:

  • Constructor Details

    • MonotoneChain

      public MonotoneChain()
      Create a new MonotoneChain instance.

    • MonotoneChain

      public MonotoneChain(boolean includeCollinearPoints)
      Create a new MonotoneChain instance.
      Parameters:
      includeCollinearPoints - whether collinear points shall be added as hull vertices

    • MonotoneChain

      public MonotoneChain(boolean includeCollinearPoints, double tolerance)
      Create a new MonotoneChain instance.
      Parameters:
      includeCollinearPoints - whether collinear points shall be added as hull vertices
      tolerance - tolerance below which points are considered identical

  • Method Details

    • findHullVertices

      public Collection<Vector2D> findHullVertices(Collection<Vector2D> points)
      Find the convex hull vertices from the set of input points.
      Parameters:
      points - the set of input points
      Returns:
      the convex hull vertices in CCW winding

    • getTolerance

      public double getTolerance()
      Get the tolerance below which points are considered identical.
      Returns:
      the tolerance below which points are considered identical

    • isIncludeCollinearPoints

      public boolean isIncludeCollinearPoints()
      Returns if collinear points on the hull will be added as hull vertices.
      Returns:
      true if collinear points are added as hull vertices, or false if only extreme points are present.

    • generate

      public ConvexHull2D generate(Collection<Vector2D> points) throws MathIllegalStateException
      Builds the convex hull from the set of input points.
      Specified by:
      generate in interface ConvexHullGenerator<Euclidean2D,Vector2D>
      Specified by:
      generate in interface ConvexHullGenerator2D
      Parameters:
      points - the set of input points
      Returns:
      the convex hull
      Throws:
      MathIllegalStateException - if generator fails to generate a convex hull for the given set of input points