Object
- Joint<T>
- - AngleJoint<T>

Type Parameters:

T - the PhysicsBody type

All Implemented Interfaces:

DataContainer, Shiftable, Ownable
```
public class AngleJoint<T extends PhysicsBody>
extends Joint<T>
implements Shiftable, DataContainer
```
Implementation of an angle joint.
A angle joint constrains the relative rotation of two bodies. The bodies will continue to translate freely.
By default the lower and upper limit angles are set to the current angle between the bodies. When the lower and upper limits are equal, the bodies rotate together and are not allowed rotate relative to one another. By default the limits are disabled.
If the lower and upper limits are set explicitly, the values must follow these restrictions:
- lower limit ≤ upper limit
- lower limit > -180
- upper limit < 180
To create a joint with limits outside of this range use the setReferenceAngle(double) method. This method sets the baseline angle for the joint, which represents 0 radians in the context of the limits. For example:
```
 // we would like the joint limits to be [30, 260]
 // this is the same as the limits [-60, 170] if the reference angle is 90
 joint.setLimits(Math.toRadians(-60), Math.toRadians(170));
 joint.setReferenceAngle(Math.toRadians(90));
 
```
The angle joint also allows a ratio value that allow the bodies to rotate at a specified value relative to the other. This can be used to simulate gears.
Since the AngleJoint class defaults the upper and lower limits to the same value and by default the limits are enabled, you will need to modify the limits, or disable the limit to see the effect of the ratio.
When the angle between the bodies reaches a limit, and limits are enabled, the ratio will be turned off.
NOTE: The getAnchor1() and getAnchor2() methods return the world space center points for the joined bodies. This constraint doesn't need anchor points.
Since:

2.2.2

Version:

4.2.0

Author:

William Bittle

See Also:

Documentation, Angle Constraint

Field Summary

Fields
Modifier and Type	Field	Description
`protected boolean`	`limitEnabled`	Whether the limits are enabled
`protected double`	`lowerLimit`	The lower limit
`protected double`	`ratio`	The angular velocity ratio
`protected double`	`referenceAngle`	The initial angle between the two bodies
`protected double`	`upperLimit`	The upper limit

Fields inherited from class Joint
body1, body2, collisionAllowed, owner, userData

Constructor Summary

Constructors
Constructor Description

AngleJoint(T body1, T body2)
Minimal constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Vector2`	`getAnchor1()`	Returns the anchor point on the first `PhysicsBody` in world coordinates.
`Vector2`	`getAnchor2()`	Returns the anchor point on the second `PhysicsBody` in world coordinates.
`double`	`getJointAngle()`	Returns the relative angle between the two `PhysicsBody`s in radians in the range [-π, π].
`double`	`getLowerLimit()`	Returns the lower limit in radians.
`double`	`getRatio()`	Returns the angular velocity ratio between the two bodies.
`Vector2`	`getReactionForce(double invdt)`	Returns the force applied to the `PhysicsBody`s in order to satisfy the constraint in newtons.
`double`	`getReactionTorque(double invdt)`	Returns the torque applied to the `PhysicsBody`s in order to satisfy the constraint in newton-meters.
`double`	`getReferenceAngle()`	Returns the reference angle.
`double`	`getUpperLimit()`	Returns the upper limit in radians.
`void`	`initializeConstraints(TimeStep step, Settings settings)`	Performs any initialization of the velocity and position constraints.
`boolean`	`isLimitEnabled()`	Returns true if the limit is enabled.
`void`	`setLimitEnabled(boolean flag)`	Sets whether the angle limits are enabled.
`void`	`setLimits(double limit)`	Sets both the lower and upper limits to the given limit.
`void`	`setLimits(double lowerLimit, double upperLimit)`	Sets both the lower and upper limits.
`void`	`setLimitsEnabled(double limit)`	Sets both the lower and upper limits to the given limit and enables them.
`void`	`setLimitsEnabled(double lowerLimit, double upperLimit)`	Sets both the lower and upper limits and enables them.
`void`	`setLowerLimit(double lowerLimit)`	Sets the lower limit in radians.
`void`	`setRatio(double ratio)`	Sets the angular velocity ratio between the two bodies.
`void`	`setReferenceAngle(double angle)`	Sets the reference angle.
`void`	`setUpperLimit(double upperLimit)`	Sets the upper limit in radians.
`void`	`shift(Vector2 shift)`	Translates the object to match the given coordinate shift.
`boolean`	`solvePositionConstraints(TimeStep step, Settings settings)`	Solves the position constraints.
`void`	`solveVelocityConstraints(TimeStep step, Settings settings)`	Solves the velocity constraints.
`String`	`toString()`

Methods inherited from class Joint
getBody1, getBody2, getConstraintImpulseMixing, getErrorReductionParameter, getNaturalFrequency, getOtherBody, getOwner, getReducedInertia, getReducedMass, getSpringDampingCoefficient, getSpringStiffness, getUserData, isCollisionAllowed, isEnabled, setCollisionAllowed, setOwner, setUserData

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface DataContainer
getUserData, setUserData

- Field Detail
  - ratio
```
protected double ratio
```
    The angular velocity ratio
  - lowerLimit
```
protected double lowerLimit
```
    The lower limit
  - upperLimit
```
protected double upperLimit
```
    The upper limit
  - limitEnabled
```
protected boolean limitEnabled
```
    Whether the limits are enabled
  - referenceAngle
```
protected double referenceAngle
```
    The initial angle between the two bodies
- Constructor Detail
  - AngleJoint
```
public AngleJoint(T body1,
                  T body2)
```
    Minimal constructor.
    
    Parameters:
    
    body1 - the first PhysicsBody
    
    body2 - the second PhysicsBody
    
    Throws:
    
    NullPointerException - if body1 or body2 is null
    
    IllegalArgumentException - if body1 == body2
- Method Detail
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Joint<T extends PhysicsBody>
  - initializeConstraints
```
public void initializeConstraints(TimeStep step,
                                  Settings settings)
```
    Description copied from class: Joint
    
    Performs any initialization of the velocity and position constraints.
    
    Specified by:
    
    initializeConstraints in class Joint<T extends PhysicsBody>
    
    Parameters:
    
    step - the time step information
    
    settings - the current world settings
  - solveVelocityConstraints
```
public void solveVelocityConstraints(TimeStep step,
                                     Settings settings)
```
    Description copied from class: Joint
    
    Solves the velocity constraints.
    
    Specified by:
    
    solveVelocityConstraints in class Joint<T extends PhysicsBody>
    
    Parameters:
    
    step - the time step information
    
    settings - the current world settings
  - solvePositionConstraints
```
public boolean solvePositionConstraints(TimeStep step,
                                        Settings settings)
```
    Description copied from class: Joint
    
    Solves the position constraints.
    
    Specified by:
    
    solvePositionConstraints in class Joint<T extends PhysicsBody>
    
    Parameters:
    
    step - the time step information
    
    settings - the current world settings
    
    Returns:
    
    boolean true if the position constraints were solved
  - getAnchor1
```
public Vector2 getAnchor1()
```
    Returns the anchor point on the first PhysicsBody in world coordinates.
    Not applicable to this joint. This method returns the first body's world center.
    
    Specified by:
    
    getAnchor1 in class Joint<T extends PhysicsBody>
    
    Returns:
    
    Vector2
  - getAnchor2
```
public Vector2 getAnchor2()
```
    Returns the anchor point on the second PhysicsBody in world coordinates.
    Not applicable to this joint. This method returns the second body's world center.
    
    Specified by:
    
    getAnchor2 in class Joint<T extends PhysicsBody>
    
    Returns:
    
    Vector2
  - getReactionForce
```
public Vector2 getReactionForce(double invdt)
```
    Returns the force applied to the PhysicsBodys in order to satisfy the constraint in newtons.
    Not applicable to this joint. Returns a new zero Vector2.
    
    Specified by:
    
    getReactionForce in class Joint<T extends PhysicsBody>
    
    Parameters:
    
    invdt - the inverse delta time
    
    Returns:
    
    Vector2
  - getReactionTorque
```
public double getReactionTorque(double invdt)
```
    Description copied from class: Joint
    
    Returns the torque applied to the PhysicsBodys in order to satisfy the constraint in newton-meters.
    
    Specified by:
    
    getReactionTorque in class Joint<T extends PhysicsBody>
    
    Parameters:
    
    invdt - the inverse delta time
    
    Returns:
    
    double
  - shift
```
public void shift(Vector2 shift)
```
    Description copied from interface: Shiftable
    
    Translates the object to match the given coordinate shift.
    
    Specified by:
    
    shift in interface Shiftable
    
    Parameters:
    
    shift - the amount to shift along the x and y axes
  - getJointAngle
```
public double getJointAngle()
```
    Returns the relative angle between the two PhysicsBodys in radians in the range [-π, π].
    
    Returns:
    
    double
    
    Since:
    
    3.1.0
  - getRatio
```
public double getRatio()
```
    Returns the angular velocity ratio between the two bodies.
    
    Returns:
    
    double
    
    Since:
    
    3.1.0
  - setRatio
```
public void setRatio(double ratio)
```
    Sets the angular velocity ratio between the two bodies.
    A value of 0.5 means that body1 will rotate 2 times while body2 rotates once. A value of 2 means that body2 will rotate 2 times while body1 rotates once.
    A value of 1.0 means that the body rotate at the same rate.
    A negative ratio indicates that the anglular velocities of the joined bodies should be in opposite directions.
    A ratio of zero is not supported.
    
    Parameters:
    
    ratio - the ratio; anything, just not zero
    
    Throws:
    
    IllegalArgumentException - if ratio is equal to zero
    
    Since:
    
    3.1.0
  - setLimitEnabled
```
public void setLimitEnabled(boolean flag)
```
    Sets whether the angle limits are enabled.
    
    Parameters:
    
    flag - true if the angle limits should be enforced
  - isLimitEnabled
```
public boolean isLimitEnabled()
```
    Returns true if the limit is enabled.
    
    Returns:
    
    boolean true if the limit is enabled
    
    Since:
    
    3.0.1
  - getUpperLimit
```
public double getUpperLimit()
```
    Returns the upper limit in radians.
    
    Returns:
    
    double
  - setUpperLimit
```
public void setUpperLimit(double upperLimit)
```
    Sets the upper limit in radians.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    upperLimit - the upper limit in radians
    
    Throws:
    
    IllegalArgumentException - if upperLimit is less than the current lower limit
  - getLowerLimit
```
public double getLowerLimit()
```
    Returns the lower limit in radians.
    
    Returns:
    
    double
  - setLowerLimit
```
public void setLowerLimit(double lowerLimit)
```
    Sets the lower limit in radians.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    lowerLimit - the lower limit in radians
    
    Throws:
    
    IllegalArgumentException - if lowerLimit is greater than the current upper limit
  - setLimits
```
public void setLimits(double lowerLimit,
                      double upperLimit)
```
    Sets both the lower and upper limits.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    lowerLimit - the lower limit in radians
    
    upperLimit - the upper limit in radians
    
    Throws:
    
    IllegalArgumentException - if lowerLimit is greater than upperLimit
  - setLimitsEnabled
```
public void setLimitsEnabled(double lowerLimit,
                             double upperLimit)
```
    Sets both the lower and upper limits and enables them.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    lowerLimit - the lower limit in radians
    
    upperLimit - the upper limit in radians
    
    Throws:
    
    IllegalArgumentException - if lowerLimit is greater than upperLimit
  - setLimits
```
public void setLimits(double limit)
```
    Sets both the lower and upper limits to the given limit.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    limit - the desired limit
  - setLimitsEnabled
```
public void setLimitsEnabled(double limit)
```
    Sets both the lower and upper limits to the given limit and enables them.
    See the class documentation for more details on the limit ranges.
    
    Parameters:
    
    limit - the desired limit
  - getReferenceAngle
```
public double getReferenceAngle()
```
    Returns the reference angle.
    The reference angle is the angle calculated when the joint was created from the two joined bodies. The reference angle is the angular difference between the bodies.
    
    Returns:
    
    double
    
    Since:
    
    3.0.1
  - setReferenceAngle
```
public void setReferenceAngle(double angle)
```
    Sets the reference angle.
    This method can be used to set the reference angle to override the computed reference angle from the constructor. This is useful in recreating the joint from a current state.
    See the class documentation for more details.
    
    Parameters:
    
    angle - the reference angle in radians
    
    Since:
    
    3.0.1
    
    See Also:
    
    getReferenceAngle()

Class AngleJoint<T extends PhysicsBody>

Field Summary

Fields inherited from class Joint

Constructor Summary

Method Summary

Methods inherited from class Joint

Methods inherited from class Object

Methods inherited from interface DataContainer

Field Detail

ratio

lowerLimit

upperLimit

limitEnabled

referenceAngle

Constructor Detail

AngleJoint

Method Detail

toString

initializeConstraints

solveVelocityConstraints

solvePositionConstraints

getAnchor1

getAnchor2

getReactionForce

getReactionTorque

shift

getJointAngle

getRatio

setRatio

setLimitEnabled

isLimitEnabled

getUpperLimit

setUpperLimit

getLowerLimit

setLowerLimit

setLimits

setLimitsEnabled

setLimits

setLimitsEnabled

getReferenceAngle

setReferenceAngle