com.vividsolutions.jts.algorithm
Class VectorMath

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

public class VectorMath
extends java.lang.Object

Functions for performing mathematics on vectors in the 2D plane. Vectors are represented as single Coordinates; the implied vector is assumed to start at the origin.

Vector arithmetic is useful in computing various geometric constructions.

Version:

1.0

Author:

Martin Davis

Constructor Summary

VectorMath()

Method Summary

static Coordinate	average(Coordinate v0, Coordinate v1) Computes the average of two vectors.
static Coordinate	difference(Coordinate v0, Coordinate v1) Computes the difference of two vectors [v0 - v1].
static double	dotProduct(Coordinate v1, Coordinate v2) Computes the dot-product of two vectors
static Coordinate	multiply(double s, Coordinate v) Computes the product of a scalar and a vector.
static Coordinate	normalize(Coordinate v) Normalizes a vector to have magnitude 1
static void	normalizeSelf(Coordinate v) Normalizes a vector to have magnitude 1 in-place
static Coordinate	pointAlong(Coordinate v0, Coordinate v1, double lengthFraction) Computes a point a given fraction of length along the line joining the endpoints of two vectors.
static Coordinate	rotateByQuarterCircle(Coordinate v, int numQuarters) Rotates a vector by a given number of quarter-circles (i.e.
static Coordinate	sum(Coordinate v0, Coordinate v1) Computes the sum of two vectors.

Methods inherited from class java.lang.Object

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

Constructor Detail

VectorMath

public VectorMath()

Method Detail

normalize

public static Coordinate normalize(Coordinate v)

Normalizes a vector to have magnitude 1

Parameters:

v - the vector to normalize

Returns:

the normalized vector

normalizeSelf

public static void normalizeSelf(Coordinate v)

Normalizes a vector to have magnitude 1 in-place

Parameters:

v - the vector to normalize

dotProduct

public static double dotProduct(Coordinate v1,
                                Coordinate v2)

Computes the dot-product of two vectors

Parameters:

v1 - a vector

v2 - a vector

Returns:

the dot product of the vectors

average

public static Coordinate average(Coordinate v0,
                                 Coordinate v1)

Computes the average of two vectors. This is equivalent to computing the midpoint of the line segment joining the vector endpoints.

Parameters:

v0 - a vector

v1 - a vector

Returns:

the average of the vectors

multiply

public static Coordinate multiply(double s,
                                  Coordinate v)

Computes the product of a scalar and a vector.

Parameters:

s - a scalar value

v - a vector

Returns:

the product of the scalar and the vector

pointAlong

public static Coordinate pointAlong(Coordinate v0,
                                    Coordinate v1,
                                    double lengthFraction)

Computes a point a given fraction of length along the line joining the endpoints of two vectors.

This is equivalent to computing the weighted sum of the two vectors:

   ws = frac * v0 + (1 - frac) * v1
 

Parameters:

v0 - a vector

v1 - a vector

lengthFraction - the fraction of the length

Returns:

the vector to the computed point

sum

public static Coordinate sum(Coordinate v0,
                             Coordinate v1)

Computes the sum of two vectors.

Parameters:

v0 - a vector

v1 - a vector

Returns:

the sum of the vectors

difference

public static Coordinate difference(Coordinate v0,
                                    Coordinate v1)

Computes the difference of two vectors [v0 - v1].

Parameters:

v0 - a vector

v1 - a vector

Returns:

the sum of the vectors

rotateByQuarterCircle

public static Coordinate rotateByQuarterCircle(Coordinate v,
                                               int numQuarters)

Rotates a vector by a given number of quarter-circles (i.e. multiples of 90 degrees or Pi/2 radians). A positive number rotates counter-clockwise, a negative number rotates clockwise. Under this operation the magnitude of the vector and the absolute values of the ordinates do not change, only their sign and ordinate index.

Parameters:

v - the vector to rotate.

numQuarters - the number of quarter-circles to rotate by

Returns:

the rotated vector.