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LineIntersector()
computeEdgeDistance(Coordinate, Coordinate, Coordinate): double
nonRobustComputeEdgeDistance(Coordinate, Coordinate, Coordinate): double
setMakePrecise(PrecisionModel): void
setPrecisionModel(PrecisionModel): void
getEndpoint(int, int): Coordinate
computeIntersection(Coordinate, Coordinate, Coordinate): void
isCollinear(): boolean
computeIntersection(Coordinate, Coordinate, Coordinate, Coordinate): void
computeIntersect(Coordinate, Coordinate, Coordinate, Coordinate): int
toString(): String
isEndPoint(): boolean
hasIntersection(): boolean
getIntersectionNum(): int
getIntersection(int): Coordinate
computeIntLineIndex(): void
isIntersection(Coordinate): boolean
isInteriorIntersection(): boolean
isInteriorIntersection(int): boolean
isProper(): boolean
getIntersectionAlongSegment(int, int): Coordinate
getIndexAlongSegment(int, int): int
computeIntLineIndex(int): void
getEdgeDistance(int, int): double
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Class LineIntersector

Hierarchy: Object , LineIntersector
Direct Known Subclasses: RobustLineIntersector
public abstract class LineIntersector
A LineIntersector is an algorithm that can both test whether two line segments intersect and compute the intersection point(s) if they do.

There are three possible outcomes when determining whether two line segments intersect:

For segments which intersect in a single point, the point may be either an endpoint or in the interior of each segment. If the point lies in the interior of both segments, this is termed a proper intersection. The method isProper() test for this situation.

The intersection point(s) may be computed in a precise or non-precise manner. Computing an intersection point precisely involves rounding it via a supplied PrecisionModel.

LineIntersectors do not perform an initial envelope intersection test to determine if the segments are disjoint. This is because this class is likely to be used in a context where envelope overlap is already known to occur (or be likely).

Other

  • version: 1.7
public LineIntersector()
public static double computeEdgeDistance(Coordinate p, Coordinate p0, Coordinate p1)
Computes the "edge distance" of an intersection point p along a segment. The edge distance is a metric of the point along the edge. The metric used is a robust and easy to compute metric function. It is not equivalent to the usual Euclidean metric. It relies on the fact that either the x or the y ordinates of the points in the edge are unique, depending on whether the edge is longer in the horizontal or vertical direction.

NOTE: This function may produce incorrect distances for inputs where p is not precisely on p1-p2 (E.g. p = (139,9) p1 = (139,10), p2 = (280,1) produces distance 0.0, which is incorrect.

My hypothesis is that the function is safe to use for points which are the result of rounding points which lie on the line, but not safe to use for truncated points.

public static double nonRobustComputeEdgeDistance(Coordinate p, Coordinate p1, Coordinate p2)
This function is non-robust, since it may compute the square of large numbers. Currently not sure how to improve this.
public void setMakePrecise(PrecisionModel precisionModel)
Force computed intersection to be rounded to a given precision model
Parameters:
precisionModel - precisionModel
Deprecation:
use setPrecisionModel instead
public void setPrecisionModel(PrecisionModel precisionModel)
Force computed intersection to be rounded to a given precision model. No getter is provided, because the precision model is not required to be specified.
Parameters:
precisionModel - precisionModel
public Coordinate getEndpoint(int segmentIndex, int ptIndex)
Gets an endpoint of an input segment.
Parameters:
segmentIndex - segmentIndex the index of the input segment (0 or 1)
ptIndex - ptIndex the index of the endpoint (0 or 1)
Returns:
the specified endpoint
public abstract abstract void computeIntersection(Coordinate p, Coordinate p1, Coordinate p2)
Compute the intersection of a point p and the line p1-p2. This function computes the boolean value of the hasIntersection test. The actual value of the intersection (if there is one) is equal to the value of p.
protected boolean isCollinear()
public void computeIntersection(Coordinate p1, Coordinate p2, Coordinate p3, Coordinate p4)
Computes the intersection of the lines p1-p2 and p3-p4. This function computes both the boolean value of the hasIntersection test and the (approximate) value of the intersection point itself (if there is one).
protected abstract abstract int computeIntersect(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)
public String toString()
protected boolean isEndPoint()
public boolean hasIntersection()
Tests whether the input geometries intersect.
Returns:
true if the input geometries intersect
public int getIntersectionNum()
Returns the number of intersection points found. This will be either 0, 1 or 2.
Returns:
the number of intersection points found (0, 1, or 2)
public Coordinate getIntersection(int intIndex)
Returns the intIndex'th intersection point
Parameters:
intIndex - intIndex is 0 or 1
Returns:
the intIndex'th intersection point
protected void computeIntLineIndex()
public boolean isIntersection(Coordinate pt)
Test whether a point is a intersection point of two line segments. Note that if the intersection is a line segment, this method only tests for equality with the endpoints of the intersection segment. It does not return true if the input point is internal to the intersection segment.
Returns:
true if the input point is one of the intersection points.
public boolean isInteriorIntersection()
Tests whether either intersection point is an interior point of one of the input segments.
Returns:
true if either intersection point is in the interior of one of the input segments
public boolean isInteriorIntersection(int inputLineIndex)
Tests whether either intersection point is an interior point of the specified input segment.
Returns:
true if either intersection point is in the interior of the input segment
public boolean isProper()
Tests whether an intersection is proper.
The intersection between two line segments is considered proper if they intersect in a single point in the interior of both segments (e.g. the intersection is a single point and is not equal to any of the endpoints).

The intersection between a point and a line segment is considered proper if the point lies in the interior of the segment (e.g. is not equal to either of the endpoints).

Returns:
true if the intersection is proper
public Coordinate getIntersectionAlongSegment(int segmentIndex, int intIndex)
Computes the intIndex'th intersection point in the direction of a specified input line segment
Parameters:
segmentIndex - segmentIndex is 0 or 1
intIndex - intIndex is 0 or 1
Returns:
the intIndex'th intersection point in the direction of the specified input line segment
public int getIndexAlongSegment(int segmentIndex, int intIndex)
Computes the index (order) of the intIndex'th intersection point in the direction of a specified input line segment
Parameters:
segmentIndex - segmentIndex is 0 or 1
intIndex - intIndex is 0 or 1
Returns:
the index of the intersection point along the input segment (0 or 1)
protected void computeIntLineIndex(int segmentIndex)
public double getEdgeDistance(int segmentIndex, int intIndex)
Computes the "edge distance" of an intersection point along the specified input line segment.
Parameters:
segmentIndex - segmentIndex is 0 or 1
intIndex - intIndex is 0 or 1
Returns:
the edge distance of the intersection point