QuadEdge (Revolution Systems Open Library TRUNK-SNAPSHOT API)

java.lang.Object
- com.revolsys.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 vertice or faces; a vertex is implicitly defined as a ring of edges (created using the next field).

Author:

David Skea, Martin Davis

Method Summary

Methods
Modifier and Type	Method and 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.
`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(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 `LineSegmentDouble` representing the geometry of this edge.
`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
  - 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.
  - 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
  - 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
  - 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.
  - dest
```
public final Vertex dest()
```
    Gets the vertex for the edge's destination
    
    Returns:
    the destination vertex
  - 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.
  - 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
  - getData
```
public Object getData()
```
    Gets the external data value for this edge.
    
    Returns:
    the data object
  - getLength
```
public double getLength()
```
    Gets the length of the geometry of this quadedge.
    
    Returns:
    the length of the quadedge
  - 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 Coordinates ordering
    
    Returns:
    the primary quadedge
  - invRot
```
public final QuadEdge invRot()
```
    Gets the dual of this edge, directed from its left to its right.
    
    Returns:
    the inverse rotated edge.
  - isLive
```
public boolean isLive()
```
    Tests whether this edge has been deleted.
    
    Returns:
    true if this edge has not been deleted.
  - 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.
  - 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.
  - orig
```
public final Vertex orig()
```
    Gets the vertex for the edge's origin
    
    Returns:
    the origin vertex
  - rNext
```
public final QuadEdge rNext()
```
    Gets the edge around the right face ccw following this edge.
    
    Returns:
    the next right face edge.
  - rot
```
public final QuadEdge rot()
```
    Gets the dual of this edge, directed from its right to its left.
    
    Returns:
    the rotated edge
  - rPrev
```
public final QuadEdge rPrev()
```
    Gets the edge around the right face ccw before this edge.
    
    Returns:
    the previous right face edge.
  - setData
```
public void setData(Object data)
```
    Sets the external data value for this edge.
    
    Parameters:
    data - an object containing external data
  - setNext
```
public void setNext(QuadEdge next)
```
    Sets the connected edge
    
    Parameters:
    next - edge
  - sym
```
public final QuadEdge sym()
```
    Gets the edge from the destination to the origin of this edge.
    
    Returns:
    the sym of the edge
  - toLineSegment
```
public LineSegment toLineSegment()
```
    Creates a LineSegmentDouble representing the geometry of this edge.
    
    Returns:
    a LineSegmentDouble
  - 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

Class QuadEdge

Method Summary

Methods inherited from class java.lang.Object

Method Detail

connect

makeEdge

splice

swap

delete

dest

dNext

dPrev

equalsNonOriented

equalsOriented

getData

getLength

getPrimary

invRot

isLive

lNext

lPrev

oNext

oPrev

orig

rNext

rot

rPrev

setData

setNext

sym

toLineSegment

toString