Class AklToussaintHeuristic

java.lang.Object
org.apache.commons.math3.geometry.euclidean.twod.hull.AklToussaintHeuristic

public final class AklToussaintHeuristic extends Object
A simple heuristic to improve the performance of convex hull algorithms.

The heuristic is based on the idea of a convex quadrilateral, which is formed by four points with the lowest and highest x / y coordinates. Any point that lies inside this quadrilateral can not be part of the convex hull and can thus be safely discarded before generating the convex hull itself.

The complexity of the operation is O(n), and may greatly improve the time it takes to construct the convex hull afterwards, depending on the point distribution.

Since:
3.3
See Also:
  • Constructor Details

    • AklToussaintHeuristic

      private AklToussaintHeuristic()
      Hide utility constructor.
  • Method Details

    • reducePoints

      public static Collection<Vector2D> reducePoints(Collection<Vector2D> points)
      Returns a point set that is reduced by all points for which it is safe to assume that they are not part of the convex hull.
      Parameters:
      points - the original point set
      Returns:
      a reduced point set, useful as input for convex hull algorithms
    • buildQuadrilateral

      private static List<Vector2D> buildQuadrilateral(Vector2D... points)
      Build the convex quadrilateral with the found corner points (with min/max x/y coordinates).
      Parameters:
      points - the respective points with min/max x/y coordinate
      Returns:
      the quadrilateral
    • insideQuadrilateral

      private static boolean insideQuadrilateral(Vector2D point, List<Vector2D> quadrilateralPoints)
      Checks if the given point is located within the convex quadrilateral.
      Parameters:
      point - the point to check
      quadrilateralPoints - the convex quadrilateral, represented by 4 points
      Returns:
      true if the point is inside the quadrilateral, false otherwise