## com.vividsolutions.jts.algorithm
Class RayCrossingCounter

    java.lang.Object
      com.vividsolutions.jts.algorithm.RayCrossingCounter

public class RayCrossingCounter
extends java.lang.Object

Counts the number of segments crossed by a horizontal ray extending to the right from a given point, in an incremental fashion. This can be used to determine whether a point lies in a `Polygonal` geometry. The class determines the situation where the point lies exactly on a segment. When being used for Point-In-Polygon determination, this case allows short-circuiting the evaluation.

This class handles polygonal geometries with any number of shells and holes. The orientation of the shell and hole rings is unimportant. In order to compute a correct location for a given polygonal geometry, it is essential that all segments are counted which

- touch the ray
- lie in in any ring which may contain the point

The only exception is when the point-on-segment situation is detected, in which case no further processing is required. The implication of the above rule is that segments which can be a priori determined to not touch the ray (i.e. by a test of their bounding box or Y-extent) do not need to be counted. This allows for optimization by indexing.

Author:
  Martin Davis

Constructor Summary
`RayCrossingCounter(Coordinate p)`

Method Summary
`void` `countSegment(Coordinate p1, Coordinate p2)` Counts a segment
`int` `getLocation()` Gets the `Location` of the point relative to the ring, polygon or multipolygon from which the processed segments were provided.
`boolean` `isOnSegment()` Reports whether the point lies exactly on one of the supplied segments.
`boolean` `isPointInPolygon()` Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided.
`static int` `locatePointInRing(Coordinate p, Coordinate[] ring)` Determines the `Location` of a point in a ring.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### RayCrossingCounter

    public RayCrossingCounter(Coordinate p)

Method Detail

### locatePointInRing

    public static int locatePointInRing(Coordinate p,
                                        Coordinate[] ring)

  Determines the `Location` of a point in a ring. This method is an exemplar of how to use this class.

  Parameters:
    `p` - the point to test
    `ring` - an array of Coordinates forming a ring
  Returns:
    the location of the point in the ring

### countSegment

    public void countSegment(Coordinate p1,
                             Coordinate p2)

  Counts a segment

  Parameters:
    `p1` - an endpoint of the segment
    `p2` - another endpoint of the segment

### isOnSegment

    public boolean isOnSegment()

  Reports whether the point lies exactly on one of the supplied segments. This method may be called at any time as segments are processed. If the result of this method is `true`, no further segments need be supplied, since the result will never change again.

  Returns:
    true if the point lies exactly on a segment

### getLocation

    public int getLocation()

  Gets the `Location` of the point relative to the ring, polygon or multipolygon from which the processed segments were provided.

  This method only determines the correct location if all relevant segments must have been processed.

  Returns:
    the Location of the point

### isPointInPolygon

    public boolean isPointInPolygon()

  Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided.

  This method only determines the correct location if all relevant segments must have been processed.

  Returns:
    true if the point lies in or on the supplied polygon