org.locationtech.jts.algorithm

Class PolygonNodeTopology

java.lang.Object

org.locationtech.jts.algorithm.PolygonNodeTopology

public class PolygonNodeTopology
extends Object

Functions to compute topological information about nodes (ring intersections) in polygonal geometry.

Author:

mdavis

Constructor Summary

Constructors

Constructor and Description
PolygonNodeTopology()

Method Summary

Modifier and Type	Method and Description
static int	compareAngle(Coordinate origin, Coordinate p, Coordinate q) Compares the angles of two vectors relative to the positive X-axis at their origin.
static boolean	isCrossing(Coordinate nodePt, Coordinate a0, Coordinate a1, Coordinate b0, Coordinate b1) Check if four segments at a node cross.
static boolean	isInteriorSegment(Coordinate nodePt, Coordinate a0, Coordinate a1, Coordinate b) Tests whether an segment node-b lies in the interior or exterior of a corner of a ring formed by the two segments a0-node-a1.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PolygonNodeTopology

public PolygonNodeTopology()

Method Detail

isCrossing

public static boolean isCrossing(Coordinate nodePt,
                                 Coordinate a0,
                                 Coordinate a1,
                                 Coordinate b0,
                                 Coordinate b1)

Check if four segments at a node cross. Typically the segments lie in two different rings, or different sections of one ring. The node is topologically valid if the rings do not cross. If any segments are collinear, the test returns false.

Parameters:

nodePt - the node location

a0 - the previous segment endpoint in a ring

a1 - the next segment endpoint in a ring

b0 - the previous segment endpoint in the other ring

b1 - the next segment endpoint in the other ring

Returns:

true if the rings cross at the node

isInteriorSegment

public static boolean isInteriorSegment(Coordinate nodePt,
                                        Coordinate a0,
                                        Coordinate a1,
                                        Coordinate b)

Tests whether an segment node-b lies in the interior or exterior of a corner of a ring formed by the two segments a0-node-a1. The ring interior is assumed to be on the right of the corner (i.e. a CW shell or CCW hole). The test segment must not be collinear with the corner segments.

Parameters:

nodePt - the node location

a0 - the first vertex of the corner

a1 - the second vertex of the corner

b - the other vertex of the test segment

Returns:

true if the segment is interior to the ring corner

compareAngle

public static int compareAngle(Coordinate origin,
                               Coordinate p,
                               Coordinate q)

Compares the angles of two vectors relative to the positive X-axis at their origin. Angles increase CCW from the X-axis.

Parameters:

origin - the origin of the vectors

p - the endpoint of the vector P

q - the endpoint of the vector Q

Returns:

a negative integer, zero, or a positive integer as this vector P has angle less than, equal to, or greater than vector Q