Object
- Joint<T>
- - DistanceJoint<T>

Type Parameters:

T - the PhysicsBody type

All Implemented Interfaces:

DataContainer, Shiftable, Ownable
```
public class DistanceJoint<T extends PhysicsBody>
extends Joint<T>
implements Shiftable, DataContainer
```
Implementation of a fixed length distance joint.
Given the two world space anchor points a distance is computed and used to constrain the attached PhysicsBodys at that distance. The bodies can rotate freely about the anchor points and the whole system can move and rotate freely, but the distance between the two anchor points is fixed.
This joint doubles as a spring/damper distance joint where the length can change but is constantly approaching the target distance. Enable the spring/damper by setting the frequency and damping ratio to values greater than zero. A good starting point is a frequency of 8.0 and damping ratio of 0.3 then adjust as necessary.

Since:

1.0.0

Version:

4.0.0

Author:

William Bittle

See Also:

Documentation, Distance Constraint

Constructor Summary

Constructors
Constructor Description

DistanceJoint(T body1, T body2, Vector2 anchor1, Vector2 anchor2)
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`	`getDampingRatio()`	Returns the damping ratio.
`double`	`getDistance()`	Returns the rest distance between the two constrained `PhysicsBody`s in meters.
`double`	`getFrequency()`	Returns the spring frequency.
`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.
`void`	`initializeConstraints(TimeStep step, Settings settings)`	Performs any initialization of the velocity and position constraints.
`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`	`setDistance(double distance)`	Sets the rest distance between the two constrained `PhysicsBody`s in meters.
`void`	`setFrequency(double frequency)`	Sets the spring frequency.
`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
  - DistanceJoint
```
public DistanceJoint(T body1,
                     T body2,
                     Vector2 anchor1,
                     Vector2 anchor2)
```
    Minimal constructor.
    Creates a fixed distance Joint where the joined PhysicsBodys do not participate in collision detection and resolution.
    
    Parameters:
    
    body1 - the first PhysicsBody
    
    body2 - the second PhysicsBody
    
    anchor1 - in world coordinates
    
    anchor2 - in world coordinates
    
    Throws:
    
    NullPointerException - if body1, body2, anchor1, or anchor2 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)
```
    Returns the torque applied to the PhysicsBodys in order to satisfy the constraint in newton-meters.
    Not applicable to this joint. Always returns zero.
    
    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
  - isSpring
```
@Deprecated
public boolean isSpring()
```
    Deprecated.
    Deprecated in 4.0.0. Use the isSpringEnabled() method instead.
    
    Returns true if this distance joint is a spring distance joint.
    
    Returns:
    
    boolean
  - isSpringDamper
```
@Deprecated
public boolean isSpringDamper()
```
    Deprecated.
    Deprecated in 4.0.0. Use the isSpringDamperEnabled() method instead.
    
    Returns true if this distance joint is a spring distance 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
  - getDistance
```
public double getDistance()
```
    Returns the rest distance between the two constrained PhysicsBodys in meters.
    
    Returns:
    
    double
  - setDistance
```
public void setDistance(double distance)
```
    Sets the rest distance between the two constrained PhysicsBodys in meters.
    
    Parameters:
    
    distance - the distance in meters
    
    Throws:
    
    IllegalArgumentException - if distance is less than zero
  - 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 or equal to zero
    
    Throws:
    
    IllegalArgumentException - if frequency is less than zero

Class DistanceJoint<T extends PhysicsBody>

Constructor Summary

Method Summary

Methods inherited from class Joint

Methods inherited from class Object

Methods inherited from interface DataContainer

Constructor Detail

DistanceJoint

Method Detail

toString

initializeConstraints

solveVelocityConstraints

solvePositionConstraints

getAnchor1

getAnchor2

getReactionForce

getReactionTorque

shift

isSpring

isSpringDamper

isSpringEnabled

isSpringDamperEnabled

getDistance

setDistance

getDampingRatio

setDampingRatio

getFrequency

setFrequency