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

Class MonotoneChain

  • All Implemented Interfaces:
    ConvexHullGenerator2D, ConvexHullGenerator<Euclidean2D,​Vector2D,​Line,​SubLine>
    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:
    Andrew's monotone chain algorithm (Wikibooks)

    • Constructor Detail

      • 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 Detail

      • 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.