RayCrossingCounter class

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 {@link 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.

This implementation uses the extended-precision orientation test, to provide maximum robustness and consistency within other algorithms.

@author Martin Davis

Constructors

RayCrossingCounter(Coordinate p)

Properties

crossingCount ↔ int

getter/setter pair

hashCode → int

The hash code for this object.

no setter, inherited

isPointOnSegment ↔ bool

getter/setter pair

p ↔ Coordinate

getter/setter pair

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

countSegment(Coordinate p1, Coordinate p2) → void

Counts a segment

getLocation() → int

Gets the {@link Location} of the point relative to the ring, polygon or multipolygon from which the processed segments were provided.

isOnSegment() → bool

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.

isPointInPolygon() → bool

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

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Methods

locatePointInRing(Coordinate p, CoordinateSequence ring) → int

Determines the {@link Location} of a point in a ring.

locatePointInRingList(Coordinate p, List<Coordinate> ring) → int

Determines the {@link Location} of a point in a ring. This method is an exemplar of how to use this class.