Package org.meteoinfo.jts.triangulate.quadedge

Class QuadEdge


  • public class QuadEdge
extends java.lang.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 vertice or faces; a vertex is implicitly defined as a ring of edges (created using the next field).

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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.
      void delete​()
      Marks this quadedge as being deleted.
      Vertex dest​()
      Gets the vertex for the edge's destination
      QuadEdge dNext​()
      Gets the next CCW edge around (into) the destination of this edge.
      QuadEdge dPrev​()
      Gets the next CW edge around (into) the destination of this edge.
      boolean equalsNonOriented​(QuadEdge qe)
      Tests if this quadedge and another have the same line segment geometry, regardless of orientation.
      boolean equalsOriented​(QuadEdge qe)
      Tests if this quadedge and another have the same line segment geometry with the same orientation.
      java.lang.Object getData​()
      Gets the external data value for this edge.
      double getLength​()
      Gets the length of the geometry of this quadedge.
      QuadEdge getPrimary​()
      Gets the primary edge of this quadedge and its sym.
      QuadEdge invRot​()
      Gets the dual of this edge, directed from its left to its right.
      boolean isLive​()
      Tests whether this edge has been deleted.
      QuadEdge lNext​()
      Gets the CCW edge around the left face following this edge.
      QuadEdge lPrev​()
      Gets the CCW edge around the left face before this edge.
      static QuadEdge makeEdge​(Vertex o, Vertex d)
      Creates a new QuadEdge quartet from Vertex o to Vertex d.
      QuadEdge oNext​()
      Gets the next CCW edge around the origin of this edge.
      QuadEdge oPrev​()
      Gets the next CW edge around (from) the origin of this edge.
      Vertex orig​()
      Gets the vertex for the edge's origin
      QuadEdge rNext​()
      Gets the edge around the right face ccw following this edge.
      QuadEdge rot​()
      Gets the dual of this edge, directed from its right to its left.
      QuadEdge rPrev​()
      Gets the edge around the right face ccw before this edge.
      void setData​(java.lang.Object data)
      Sets the external data value for this edge.
      void setNext​(QuadEdge next)
      Sets the connected edge
      static void splice​(QuadEdge a, QuadEdge b)
      Splices two edges together or apart.
      static void swap​(QuadEdge e)
      Turns an edge counterclockwise inside its enclosing quadrilateral.
      QuadEdge sym​()
      Gets the edge from the destination to the origin of this edge.
      LineSegment toLineSegment​()
      Creates a LineSegment representing the geometry of this edge.
      java.lang.String toString​()
      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 Detail

      • 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​(java.lang.Object data)
        Sets the external data value for this edge.
        Parameters:
        data - an object containing external data

      • getData

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