Package org.apache.commons.geometry.euclidean.twod.rotation

Class Rotation2D

java.lang.Object

org.apache.commons.geometry.euclidean.twod.rotation.Rotation2D

All Implemented Interfaces:

java.util.function.Function<Vector2D,Vector2D>, java.util.function.UnaryOperator<Vector2D>, Transform<Vector2D>, EuclideanTransform<Vector2D>

public final class Rotation2D
extends java.lang.Object
implements EuclideanTransform<Vector2D>

Class representing a rotation in 2 dimensional Euclidean space. Positive rotations are in a counter-clockwise direction.

Field Summary

Fields

Modifier and Type	Field	Description
private double	angle	The angle of the rotation in radians.
private double	cosAngle	The cosine of the angle of rotation, cached to avoid repeated computation.
private static Rotation2D	IDENTITY	Instance representing a rotation of zero radians.
private double	sinAngle	The sine of the angle of rotation, cached to avoid repeated computation.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	Rotation2D(double angle)	Create a new instance representing the given angle.

Method Summary

Modifier and Type	Method	Description
Vector2D	apply(Vector2D pt)
Vector2D	applyVector(Vector2D vec)	Apply this transform to the given vector, ignoring translations.
static Rotation2D	createVectorRotation(Vector2D u, Vector2D v)	Create a rotation instance that rotates the vector u to point in the direction of vector v.
boolean	equals(java.lang.Object obj)
double	getAngle()	Get the angle of rotation in radians.
int	hashCode()
static Rotation2D	identity()	Return an instance representing the identity rotation, ie a rotation of zero radians.
Rotation2D	inverse()	Get an instance representing the inverse transform.
static Rotation2D	of(double angle)	Create a new instance with the given angle of rotation.
boolean	preservesOrientation()	Return true if the transform preserves the orientation of the space.
AffineTransformMatrix2D	toMatrix()	Return an AffineTransformMatrix2D representing the same rotation as this instance.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.function.Function

andThen, compose

Field Detail

IDENTITY

private static final Rotation2D IDENTITY

Instance representing a rotation of zero radians.

angle

private final double angle

The angle of the rotation in radians.

cosAngle

private final double cosAngle

The cosine of the angle of rotation, cached to avoid repeated computation.

sinAngle

private final double sinAngle

The sine of the angle of rotation, cached to avoid repeated computation.

Constructor Detail

Rotation2D

private Rotation2D(double angle)

Create a new instance representing the given angle.

Parameters:

angle - the angle of rotation, in radians

Method Detail

getAngle

public double getAngle()

Get the angle of rotation in radians.

Returns:

the angle of rotation in radians

inverse

public Rotation2D inverse()

Get an instance representing the inverse transform.

Specified by:

inverse in interface Transform<Vector2D>

Returns:

an instance representing the inverse transform

preservesOrientation

public boolean preservesOrientation()

Return true if the transform preserves the orientation of the space. For example, in Euclidean 2D space, this will be true for translations, rotations, and scalings but will be false for reflections.

This method simply returns true since rotations always preserve the orientation of the space.

Specified by:

preservesOrientation in interface Transform<Vector2D>

Returns:

true if the transform preserves the orientation of the space

See Also:

Orientation

apply

public Vector2D apply(Vector2D pt)

Specified by:

apply in interface java.util.function.Function<Vector2D,Vector2D>

applyVector

public Vector2D applyVector(Vector2D vec)

Apply this transform to the given vector, ignoring translations.

This method can be used to transform vector instances representing displacements between points. For example, if v represents the difference between points p1 and p2, then transform.applyVector(v) will represent the difference between p1 and p2 after transform is applied.

This method simply calls apply(vec) since rotations treat points and vectors similarly.

Specified by:

applyVector in interface EuclideanTransform<Vector2D>

Parameters:

vec - the vector to transform

Returns:

the new, transformed vector

toMatrix

public AffineTransformMatrix2D toMatrix()

Return an AffineTransformMatrix2D representing the same rotation as this instance.

Returns:

a transform matrix representing the same rotation

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

of

public static Rotation2D of(double angle)

Create a new instance with the given angle of rotation.

Parameters:

angle - the angle of rotation in radians

Returns:

a new instance with the given angle of rotation

identity

public static Rotation2D identity()

Return an instance representing the identity rotation, ie a rotation of zero radians.

Returns:

an instance representing a rotation of zero radians

createVectorRotation

public static Rotation2D createVectorRotation(Vector2D u,
                                              Vector2D v)

Create a rotation instance that rotates the vector u to point in the direction of vector v.

Parameters:

u - input vector

v - target vector

Returns:

a rotation instance that rotates u to point in the direction of v

Throws:

java.lang.IllegalArgumentException - if either vector cannot be normalized