Package org.locationtech.jts.algorithm

Class CGAlgorithmsDD

java.lang.Object

org.locationtech.jts.algorithm.CGAlgorithmsDD

public class CGAlgorithmsDD
extends java.lang.Object

Implements basic computational geometry algorithms using DD arithmetic.

Field Summary

Fields

Modifier and Type	Field	Description
private static double	DP_SAFE_EPSILON	A value which is safely greater than the relative round-off error in double-precision numbers

Constructor Summary

Constructors

Modifier	Constructor	Description
private	CGAlgorithmsDD()

Method Summary

Modifier and Type	Method	Description
static Coordinate	intersection(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)	Computes an intersection point between two lines using DD arithmetic.
static int	orientationIndex(Coordinate p1, Coordinate p2, Coordinate q)	Returns the index of the direction of the point q relative to a vector specified by p1-p2.
private static int	orientationIndexFilter(Coordinate pa, Coordinate pb, Coordinate pc)	A filter for computing the orientation index of three coordinates.
static int	signOfDet2x2(double dx1, double dy1, double dx2, double dy2)	Computes the sign of the determinant of the 2x2 matrix with the given entries.
static int	signOfDet2x2(DD x1, DD y1, DD x2, DD y2)	Computes the sign of the determinant of the 2x2 matrix with the given entries.
private static int	signum(double x)

Methods inherited from class java.lang.Object

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

Field Detail

DP_SAFE_EPSILON

private static final double DP_SAFE_EPSILON

A value which is safely greater than the relative round-off error in double-precision numbers

See Also:

Constant Field Values

Constructor Detail

CGAlgorithmsDD

private CGAlgorithmsDD()

Method Detail

orientationIndex

public static int orientationIndex(Coordinate p1,
                                   Coordinate p2,
                                   Coordinate q)

Returns the index of the direction of the point q relative to a vector specified by p1-p2.

Parameters:

p1 - the origin point of the vector

p2 - the final point of the vector

q - the point to compute the direction to

Returns:

1 if q is counter-clockwise (left) from p1-p2

signOfDet2x2

public static int signOfDet2x2(DD x1,
                               DD y1,
                               DD x2,
                               DD y2)

Computes the sign of the determinant of the 2x2 matrix with the given entries.

Returns:

-1 if the determinant is negative,

signOfDet2x2

public static int signOfDet2x2(double dx1,
                               double dy1,
                               double dx2,
                               double dy2)

Computes the sign of the determinant of the 2x2 matrix with the given entries.

Returns:

-1 if the determinant is negative,

orientationIndexFilter

private static int orientationIndexFilter(Coordinate pa,
                                          Coordinate pb,
                                          Coordinate pc)

A filter for computing the orientation index of three coordinates.

If the orientation can be computed safely using standard DP arithmetic, this routine returns the orientation index. Otherwise, a value i > 1 is returned. In this case the orientation index must be computed using some other more robust method. The filter is fast to compute, so can be used to avoid the use of slower robust methods except when they are really needed, thus providing better average performance.

Uses an approach due to Jonathan Shewchuk, which is in the public domain.

Parameters:

pa - a coordinate

pb - a coordinate

pc - a coordinate

Returns:

the orientation index if it can be computed safely

signum

private static int signum(double x)

intersection

public static Coordinate intersection(Coordinate p1,
                                      Coordinate p2,
                                      Coordinate q1,
                                      Coordinate q2)

Computes an intersection point between two lines using DD arithmetic. Currently does not handle case of parallel lines.

Parameters:

p1 -

p2 -

q1 -

q2 -

Returns: