java.lang.Object
org.locationtech.jts.triangulate.quadedge.QuadEdge

public class QuadEdge extends Object
A class that represents the edge data structure which implements the quadedge algebra. The quadedge algebra was described in a well-known paper by Guibas and Stolfi, "Primitives for the manipulation of general subdivisions and the computation of Voronoi diagrams", ACM Transactions on Graphics, 4(2), 1985, 75-123.

Each edge object is part of a quartet of 4 edges, linked via their rot references. Any edge in the group may be accessed using a series of rot() operations. Quadedges in a subdivision are linked together via their next references. The linkage between the quadedge quartets determines the topology of the subdivision.

The edge class does not contain separate information for vertices or faces; a vertex is implicitly defined as a ring of edges (created using the next field).

Author:
David Skea, Martin Davis
  • Method Summary

    Modifier and Type
    Method
    Description
    static QuadEdge
    Creates a new QuadEdge connecting the destination of a to the origin of b, in such a way that all three have the same left face after the connection is complete.
    void
    Marks this quadedge as being deleted.
    final Vertex
    Gets the vertex for the edge's destination
    final QuadEdge
    Gets the next CCW edge around (into) the destination of this edge.
    final QuadEdge
    Gets the next CW edge around (into) the destination of this edge.
    boolean
    Tests if this quadedge and another have the same line segment geometry, regardless of orientation.
    boolean
    Tests if this quadedge and another have the same line segment geometry with the same orientation.
    Gets the external data value for this edge.
    double
    Gets the length of the geometry of this quadedge.
    Gets the primary edge of this quadedge and its sym.
    final QuadEdge
    Gets the dual of this edge, directed from its left to its right.
    boolean
    Tests whether this edge has been deleted.
    final QuadEdge
    Gets the CCW edge around the left face following this edge.
    final QuadEdge
    Gets the CCW edge around the left face before this edge.
    static QuadEdge
    Creates a new QuadEdge quartet from Vertex o to Vertex d.
    final QuadEdge
    Gets the next CCW edge around the origin of this edge.
    final QuadEdge
    Gets the next CW edge around (from) the origin of this edge.
    final Vertex
    Gets the vertex for the edge's origin
    final QuadEdge
    Gets the edge around the right face ccw following this edge.
    final QuadEdge
    rot()
    Gets the dual of this edge, directed from its right to its left.
    final QuadEdge
    Gets the edge around the right face ccw before this edge.
    void
    Sets the external data value for this edge.
    void
    Sets the connected edge
    static void
    Splices two edges together or apart.
    static void
    Turns an edge counterclockwise inside its enclosing quadrilateral.
    final QuadEdge
    sym()
    Gets the edge from the destination to the origin of this edge.
    Creates a LineSegment representing the geometry of this edge.
    Converts this edge to a WKT two-point LINESTRING indicating the geometry of this edge.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
  • Method Details

    • makeEdge

      public static QuadEdge makeEdge(Vertex o, Vertex d)
      Creates a new QuadEdge quartet from Vertex o to Vertex d.
      Parameters:
      o - the origin Vertex
      d - the destination Vertex
      Returns:
      the new QuadEdge quartet
    • connect

      public static QuadEdge connect(QuadEdge a, QuadEdge b)
      Creates a new QuadEdge connecting the destination of a to the origin of b, in such a way that all three have the same left face after the connection is complete. Additionally, the data pointers of the new edge are set.
      Returns:
      the connected edge.
    • splice

      public static void splice(QuadEdge a, QuadEdge b)
      Splices two edges together or apart. Splice affects the two edge rings around the origins of a and b, and, independently, the two edge rings around the left faces of a and b. In each case, (i) if the two rings are distinct, Splice will combine them into one, or (ii) if the two are the same ring, Splice will break it into two separate pieces. Thus, Splice can be used both to attach the two edges together, and to break them apart.
      Parameters:
      a - an edge to splice
      b - an edge to splice
    • swap

      public static void swap(QuadEdge e)
      Turns an edge counterclockwise inside its enclosing quadrilateral.
      Parameters:
      e - the quadedge to turn
    • getPrimary

      public QuadEdge getPrimary()
      Gets the primary edge of this quadedge and its sym. The primary edge is the one for which the origin and destination coordinates are ordered according to the standard Coordinate ordering
      Returns:
      the primary quadedge
    • setData

      public void setData(Object data)
      Sets the external data value for this edge.
      Parameters:
      data - an object containing external data
    • getData

      public Object getData()
      Gets the external data value for this edge.
      Returns:
      the data object
    • delete

      public void delete()
      Marks this quadedge as being deleted. This does not free the memory used by this quadedge quartet, but indicates that this edge no longer participates in a subdivision.
    • isLive

      public boolean isLive()
      Tests whether this edge has been deleted.
      Returns:
      true if this edge has not been deleted.
    • setNext

      public void setNext(QuadEdge next)
      Sets the connected edge
      Parameters:
      next - edge
    • rot

      public final QuadEdge rot()
      Gets the dual of this edge, directed from its right to its left.
      Returns:
      the rotated edge
    • invRot

      public final QuadEdge invRot()
      Gets the dual of this edge, directed from its left to its right.
      Returns:
      the inverse rotated edge.
    • sym

      public final QuadEdge sym()
      Gets the edge from the destination to the origin of this edge.
      Returns:
      the sym of the edge
    • oNext

      public final QuadEdge oNext()
      Gets the next CCW edge around the origin of this edge.
      Returns:
      the next linked edge.
    • oPrev

      public final QuadEdge oPrev()
      Gets the next CW edge around (from) the origin of this edge.
      Returns:
      the previous edge.
    • dNext

      public final QuadEdge dNext()
      Gets the next CCW edge around (into) the destination of this edge.
      Returns:
      the next destination edge.
    • dPrev

      public final QuadEdge dPrev()
      Gets the next CW edge around (into) the destination of this edge.
      Returns:
      the previous destination edge.
    • lNext

      public final QuadEdge lNext()
      Gets the CCW edge around the left face following this edge.
      Returns:
      the next left face edge.
    • lPrev

      public final QuadEdge lPrev()
      Gets the CCW edge around the left face before this edge.
      Returns:
      the previous left face edge.
    • rNext

      public final QuadEdge rNext()
      Gets the edge around the right face ccw following this edge.
      Returns:
      the next right face edge.
    • rPrev

      public final QuadEdge rPrev()
      Gets the edge around the right face ccw before this edge.
      Returns:
      the previous right face edge.
    • orig

      public final Vertex orig()
      Gets the vertex for the edge's origin
      Returns:
      the origin vertex
    • dest

      public final Vertex dest()
      Gets the vertex for the edge's destination
      Returns:
      the destination vertex
    • getLength

      public double getLength()
      Gets the length of the geometry of this quadedge.
      Returns:
      the length of the quadedge
    • equalsNonOriented

      public boolean equalsNonOriented(QuadEdge qe)
      Tests if this quadedge and another have the same line segment geometry, regardless of orientation.
      Parameters:
      qe - a quadedge
      Returns:
      true if the quadedges are based on the same line segment regardless of orientation
    • equalsOriented

      public boolean equalsOriented(QuadEdge qe)
      Tests if this quadedge and another have the same line segment geometry with the same orientation.
      Parameters:
      qe - a quadedge
      Returns:
      true if the quadedges are based on the same line segment
    • toLineSegment

      public LineSegment toLineSegment()
      Creates a LineSegment representing the geometry of this edge.
      Returns:
      a LineSegment
    • toString

      public String toString()
      Converts this edge to a WKT two-point LINESTRING indicating the geometry of this edge.
      Overrides:
      toString in class Object
      Returns:
      a String representing this edge's geometry