Package edu.cnu.mdi.geometry

Class Vector

java.lang.Object

edu.cnu.mdi.geometry.Point

edu.cnu.mdi.geometry.Vector

public class Vector
extends Point

A mutable three-dimensional Cartesian vector.

This class extends Point so that existing MDI code can use the same public x, y, and z fields for points and vectors. The distinction is semantic: a Point represents a location, while a Vector represents a displacement or direction.

Author:

heddle

Field Summary

Fields inherited from class edu.cnu.mdi.geometry.Point

x, y, z

Constructor Summary

Constructors

Constructor	Description
Vector()	Creates the zero vector.
Vector(double x, double y, double z)	Creates a vector from its Cartesian components.
Vector(Point p)	Creates a vector from a point-like tuple.

Method Summary

Modifier and Type	Method	Description
static Vector	cross(Vector a, Vector b)	Computes the cross product a x b.
static void	cross(Vector a, Vector b, Vector c)	Computes the cross product a x b and stores it in an existing vector.
double	length()	Computes this vector's Euclidean length.
double	lengthSquared()	Computes the square of this vector's Euclidean length.
Vector	unitVector()	Computes a unit vector in the same direction as this vector.

Methods inherited from class edu.cnu.mdi.geometry.Point

add, difference, difference, distance, distance, distance, dot, dot, scale, set, set, subtract, toString

Methods inherited from class java.lang.Object

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

Constructor Details

Vector

public Vector()

Creates the zero vector.

Vector

public Vector(Point p)

Creates a vector from a point-like tuple.

Parameters:

p - the tuple whose components will be copied

Throws:

NullPointerException - if p is null

Vector

public Vector(double x,
 double y,
 double z)

Creates a vector from its Cartesian components.

Parameters:

x - the x component

y - the y component

z - the z component

Method Details

lengthSquared

public double lengthSquared()

Computes the square of this vector's Euclidean length.

Returns:

x*x + y*y + z*z

length

public double length()

Computes this vector's Euclidean length.

Returns:

the vector length

cross

public static Vector cross(Vector a,
 Vector b)

Computes the cross product a x b.

Parameters:

a - the first vector

b - the second vector

Returns:

a new vector containing a x b

Throws:

NullPointerException - if either argument is null

cross

public static void cross(Vector a,
 Vector b,
 Vector c)

Computes the cross product a x b and stores it in an existing vector.

All three result components are computed into temporaries before any are written, so the output vector may safely be the same object as either input.

Parameters:

a - the first vector

b - the second vector

c - upon return, contains a x b

Throws:

NullPointerException - if any argument is null

unitVector

public Vector unitVector()

Computes a unit vector in the same direction as this vector.

Returns:

a new unit vector, or null if this vector is too close to zero to normalize