Object
- Joint<T>
- - WheelJoint<T>

Type Parameters:

T - the PhysicsBody type

All Implemented Interfaces:

DataContainer, Shiftable, Ownable
```
public class WheelJoint<T extends PhysicsBody>
extends Joint<T>
implements Shiftable, DataContainer
```
Implementation of a wheel joint.
A wheel joint is used to simulate a vehicle's wheel and suspension. The wheel is allowed to rotate freely about the given anchor point. The suspension is allowed to translate freely along the given axis. The whole system can translate and rotate freely.
By default the frequency and damping ratio are set to 8.0 and 0.0 respectively. By definition this joint requires a frequency greater than zero to perform properly. If a wheel without suspension is required, use a RevoluteJoint instead.
This joint also supports a motor. The motor is an angular motor about the anchor point. The motor speed can be positive or negative to indicate a clockwise or counter-clockwise rotation. The maximum motor torque must be greater than zero for the motor to apply any motion.
The joint also supports upper and lower limits. The limits represent the maximum displacement from the anchor point along the given axis.

Since:

3.0.0

Version:

4.0.1

Author:

William Bittle

See Also:

Documentation

Constructor Summary

Constructors
Constructor Description

WheelJoint(T body1, T body2, Vector2 anchor, Vector2 axis)
Minimal constructor.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated 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`	`getAngularSpeed()`	Returns the current angular speed between the two joined bodies.
`double`	`getAngularTranslation()`	Returns the current angular translation between the joined bodies.
`Vector2`	`getAxis()`	Returns the axis in which the joint is allowed move along in world coordinates.
`double`	`getDampingRatio()`	Returns the damping ratio.
`double`	`getFrequency()`	Returns the spring frequency.
`double`	`getJointSpeed()`	Deprecated. Replaced by `getAngularSpeed()` in 3.2.1
`double`	`getJointTranslation()`	Deprecated. Replaced by `getLinearTranslation()` in 3.2.1
`double`	`getLinearSpeed()`	Returns the linear speed along the axis between the two joined bodies
`double`	`getLinearTranslation()`	Returns the current linear translation along the joint axis.
`double`	`getLowerLimit()`	Returns the lower limit in meters.
`double`	`getMaximumMotorTorque()`	Returns the maximum torque the motor can apply to the joint to achieve the target speed.
`double`	`getMotorSpeed()`	Returns the target motor speed in radians / second.
`double`	`getMotorTorque(double invdt)`	Returns the applied motor torque.
`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`	`getUpperLimit()`	Returns the upper limit in meters.
`void`	`initializeConstraints(TimeStep step, Settings settings)`	Performs any initialization of the velocity and position constraints.
`boolean`	`isLimitEnabled()`	Returns true if the limit is enabled.
`boolean`	`isMotorEnabled()`	Returns true if the motor is enabled.
`boolean`	`isSpring()`	Deprecated. Deprecated in 4.0.0.
`boolean`	`isSpringDamper()`	Deprecated. Deprecated in 4.0.0.
`boolean`	`isSpringDamperEnabled()`	Returns true if this distance joint is a spring distance joint with damping.
`boolean`	`isSpringEnabled()`	Returns true if this distance joint is a spring distance joint.
`void`	`setDampingRatio(double dampingRatio)`	Sets the damping ratio.
`void`	`setFrequency(double frequency)`	Sets the spring frequency.
`void`	`setLimitEnabled(boolean flag)`	Enables or disables the limit.
`void`	`setLimits(double lowerLimit, double upperLimit)`	Sets the upper and lower limits.
`void`	`setLowerLimit(double lowerLimit)`	Sets the lower limit.
`void`	`setMaximumMotorTorque(double maximumMotorTorque)`	Sets the maximum torque the motor can apply to the joint to achieve the target speed.
`void`	`setMotorEnabled(boolean motorEnabled)`	Enables or disables the motor.
`void`	`setMotorSpeed(double motorSpeed)`	Sets the target motor speed.
`void`	`setUpperLimit(double upperLimit)`	Sets the upper limit.
`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, getOtherBody, getOwner, getUserData, isActive, isCollisionAllowed, isEnabled, isOnIsland, setCollisionAllowed, setOnIsland, setOwner, setUserData

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

Methods inherited from interface DataContainer
getUserData, setUserData

- Constructor Detail
  - WheelJoint
```
public WheelJoint(T body1,
                  T body2,
                  Vector2 anchor,
                  Vector2 axis)
```
    Minimal constructor.
    
    Parameters:
    
    body1 - the first PhysicsBody
    
    body2 - the second PhysicsBody
    
    anchor - the anchor point in world coordinates
    
    axis - the axis of allowed motion
    
    Throws:
    
    NullPointerException - if body1, body2, anchor, or axis 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()
```
    Description copied from class: Joint
    
    Returns the anchor point on the first PhysicsBody in world coordinates.
    
    Specified by:
    
    getAnchor1 in class Joint<T extends PhysicsBody>
    
    Returns:
    
    Vector2
  - getAnchor2
```
public Vector2 getAnchor2()
```
    Description copied from class: Joint
    
    Returns the anchor point on the second PhysicsBody in world coordinates.
    
    Specified by:
    
    getAnchor2 in class Joint<T extends PhysicsBody>
    
    Returns:
    
    Vector2
  - getReactionForce
```
public Vector2 getReactionForce(double invdt)
```
    Description copied from class: Joint
    
    Returns the force applied to the PhysicsBodys in order to satisfy the constraint in newtons.
    
    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
  - getJointSpeed
```
@Deprecated
public double getJointSpeed()
```
    Deprecated.
    Replaced by getAngularSpeed() in 3.2.1
    
    Returns the current joint speed.
    
    Returns:
    
    double
  - getLinearSpeed
```
public double getLinearSpeed()
```
    Returns the linear speed along the axis between the two joined bodies
    
    Returns:
    
    double
    
    Since:
    
    3.2.1
  - getAngularSpeed
```
public double getAngularSpeed()
```
    Returns the current angular speed between the two joined bodies.
    
    Returns:
    
    double
    
    Since:
    
    3.2.1
  - getJointTranslation
```
@Deprecated
public double getJointTranslation()
```
    Deprecated.
    Replaced by getLinearTranslation() in 3.2.1
    
    Returns the current joint translation.
    
    Returns:
    
    double
  - getLinearTranslation
```
public double getLinearTranslation()
```
    Returns the current linear translation along the joint axis.
    
    Returns:
    
    double
    
    Since:
    
    3.2.1
  - getAngularTranslation
```
public double getAngularTranslation()
```
    Returns the current angular translation between the joined bodies.
    
    Returns:
    
    double
    
    Since:
    
    3.2.1
  - isSpring
```
@Deprecated
public boolean isSpring()
```
    Deprecated.
    Deprecated in 4.0.0. Use the isSpringEnabled() method instead.
    
    Returns true if this wheel joint is a spring wheel joint.
    Since the frequency cannot be less than or equal to zero, this should always returne true.
    
    Returns:
    
    boolean
  - isSpringDamper
```
@Deprecated
public boolean isSpringDamper()
```
    Deprecated.
    Deprecated in 4.0.0. Use the isSpringDamperEnabled() method instead.
    
    Returns true if this wheel joint is a spring wheel joint with damping.
    
    Returns:
    
    boolean
  - isSpringEnabled
```
public boolean isSpringEnabled()
```
    Returns true if this distance joint is a spring distance joint.
    
    Returns:
    
    boolean
    
    Since:
    
    4.0.0
  - isSpringDamperEnabled
```
public boolean isSpringDamperEnabled()
```
    Returns true if this distance joint is a spring distance joint with damping.
    
    Returns:
    
    boolean
    
    Since:
    
    4.0.0
  - getDampingRatio
```
public double getDampingRatio()
```
    Returns the damping ratio.
    
    Returns:
    
    double
  - setDampingRatio
```
public void setDampingRatio(double dampingRatio)
```
    Sets the damping ratio.
    Larger values reduce the oscillation of the spring.
    
    Parameters:
    
    dampingRatio - the damping ratio; in the range [0, 1]
    
    Throws:
    
    IllegalArgumentException - if damping ration is less than zero or greater than 1
  - getFrequency
```
public double getFrequency()
```
    Returns the spring frequency.
    
    Returns:
    
    double
  - setFrequency
```
public void setFrequency(double frequency)
```
    Sets the spring frequency.
    Larger values increase the stiffness of the spring.
    
    Parameters:
    
    frequency - the spring frequency in hz; must be greater than zero
    
    Throws:
    
    IllegalArgumentException - if frequency is less than or equal to zero
  - isMotorEnabled
```
public boolean isMotorEnabled()
```
    Returns true if the motor is enabled.
    
    Returns:
    
    boolean
  - setMotorEnabled
```
public void setMotorEnabled(boolean motorEnabled)
```
    Enables or disables the motor.
    
    Parameters:
    
    motorEnabled - true if the motor should be enabled
  - getMotorSpeed
```
public double getMotorSpeed()
```
    Returns the target motor speed in radians / second.
    
    Returns:
    
    double
  - setMotorSpeed
```
public void setMotorSpeed(double motorSpeed)
```
    Sets the target motor speed.
    
    Parameters:
    
    motorSpeed - the target motor speed in radians / second
    
    See Also:
    
    setMaximumMotorTorque(double)
  - getMaximumMotorTorque
```
public double getMaximumMotorTorque()
```
    Returns the maximum torque the motor can apply to the joint to achieve the target speed.
    
    Returns:
    
    double
  - setMaximumMotorTorque
```
public void setMaximumMotorTorque(double maximumMotorTorque)
```
    Sets the maximum torque the motor can apply to the joint to achieve the target speed.
    
    Parameters:
    
    maximumMotorTorque - the maximum torque in newtons-meters; in the range [0, ∞]
    
    Throws:
    
    IllegalArgumentException - if maxMotorTorque is less than zero
    
    See Also:
    
    setMotorSpeed(double)
  - getMotorTorque
```
public double getMotorTorque(double invdt)
```
    Returns the applied motor torque.
    
    Parameters:
    
    invdt - the inverse delta time from the time step
    
    Returns:
    
    double
  - isLimitEnabled
```
public boolean isLimitEnabled()
```
    Returns true if the limit is enabled.
    
    Returns:
    
    boolean
  - setLimitEnabled
```
public void setLimitEnabled(boolean flag)
```
    Enables or disables the limit.
    
    Parameters:
    
    flag - true if the limit should be enabled
  - getUpperLimit
```
public double getUpperLimit()
```
    Returns the upper limit in meters.
    
    Returns:
    
    double
  - setUpperLimit
```
public void setUpperLimit(double upperLimit)
```
    Sets the upper limit.
    Must be greater than or equal to the current lower limit.
    
    Parameters:
    
    upperLimit - the upper limit in meters
    
    Throws:
    
    IllegalArgumentException - if upperLimit is less than the current lower limit
  - getLowerLimit
```
public double getLowerLimit()
```
    Returns the lower limit in meters.
    
    Returns:
    
    double
  - setLowerLimit
```
public void setLowerLimit(double lowerLimit)
```
    Sets the lower limit.
    Must be less than or equal to the current upper limit.
    
    Parameters:
    
    lowerLimit - the lower limit in meters
    
    Throws:
    
    IllegalArgumentException - if lowerLimit is greater than the current upper limit
  - setLimits
```
public void setLimits(double lowerLimit,
                      double upperLimit)
```
    Sets the upper and lower limits.
    The lower limit must be less than or equal to the upper limit.
    
    Parameters:
    
    lowerLimit - the lower limit in meters
    
    upperLimit - the upper limit in meters
    
    Throws:
    
    IllegalArgumentException - if the lowerLimit is greater than upperLimit
  - getAxis
```
public Vector2 getAxis()
```
    Returns the axis in which the joint is allowed move along in world coordinates.
    
    Returns:
    
    Vector2

Class WheelJoint<T extends PhysicsBody>

Constructor Summary

Method Summary

Methods inherited from class Joint

Methods inherited from class Object

Methods inherited from interface DataContainer

Constructor Detail

WheelJoint

Method Detail

toString

initializeConstraints

solveVelocityConstraints

solvePositionConstraints

getAnchor1

getAnchor2

getReactionForce

getReactionTorque

shift

getJointSpeed

getLinearSpeed

getAngularSpeed

getJointTranslation

getLinearTranslation

getAngularTranslation

isSpring

isSpringDamper

isSpringEnabled

isSpringDamperEnabled

getDampingRatio

setDampingRatio

getFrequency

setFrequency

isMotorEnabled

setMotorEnabled

getMotorSpeed

setMotorSpeed

getMaximumMotorTorque

setMaximumMotorTorque

getMotorTorque

isLimitEnabled

setLimitEnabled

getUpperLimit

setUpperLimit

getLowerLimit

setLowerLimit

setLimits

getAxis