Package org.jbox2d.dynamics.contacts

Class Contact

java.lang.Object

org.jbox2d.dynamics.contacts.Contact

Direct Known Subclasses:

ChainAndCircleContact, ChainAndPolygonContact, CircleContact, EdgeAndCircleContact, EdgeAndPolygonContact, PolygonAndCircleContact, PolygonContact

public abstract class Contact
extends Object

The class manages contact between two shapes. A contact exists for each overlapping AABB in the broad-phase (except if filtered). Therefore, a contact object may exist that has no contact points.

Author:

Daniel Murphy

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 85 - 384

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BULLET_HIT_FLAG	This bullet contact had a TOI event
static final int	ENABLED_FLAG	This contact can be disabled (by user)
static final int	FILTER_FLAG	This contact needs filtering because a fixture filter was changed.
Fixture	fixtureA
Fixture	fixtureB
int	flags
float	friction
int	indexA
int	indexB
static final int	ISLAND_FLAG	Flags stored in flags Used when crawling contact graph when forming islands.
final Manifold	manifold
Contact	next
ContactEdge	nodeA	Nodes for connecting bodies.
ContactEdge	nodeB
protected final WorldPool	pool
Contact	prev	World pool and list pointers.
float	restitution
float	tangentSpeed
float	toi
static final int	TOI_FLAG
float	toiCount
static final int	TOUCHING_FLAG	Set when the shapes are touching.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Contact(WorldPool argPool)

Method Summary

Modifier and Type	Method	Description
abstract void	evaluate(Manifold manifold, Transform xfA, Transform xfB)	Evaluate this contact with your own manifold and transforms.
void	flagForFiltering()	Flag this contact for filtering.
int	getChildIndexA()	Get the child primitive index for fixture A.
int	getChildIndexB()	Get the child primitive index for fixture B.
Fixture	getFixtureA()	Get fixture A in this contact.
Fixture	getFixtureB()	Get fixture B in this contact.
float	getFriction()	Get the friction.
Manifold	getManifold()	Get the contact manifold.
Contact	getNext()	Get the next contact in the world’s contact list.
float	getRestitution()	Get the restitution.
float	getTangentSpeed()	Get the desired tangent speed.
void	getWorldManifold(WorldManifold worldManifold)	Get the world manifold.
void	init(Fixture fA, int indexA, Fixture fB, int indexB)	initialization for pooling
boolean	isEnabled()	Has this contact been disabled?
boolean	isTouching()	Is this contact touching?
static float	mixFriction(float friction1, float friction2)	Friction mixing law.
static float	mixRestitution(float restitution1, float restitution2)	Restitution mixing law.
void	resetFriction()	Reset the friction mixture to the default value.
void	resetRestitution()	Reset the restitution to the default value.
void	setEnabled(boolean flag)	Enable/disable this contact.
void	setFriction(float friction)	Override the default friction mixture.
void	setRestitution(float restitution)	Override the default restitution mixture.
void	setTangentSpeed(float speed)	Set the desired tangent speed for a conveyor belt behavior.
void	update(ContactListener listener)

Methods inherited from class java.lang.Object

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

Field Details

ISLAND_FLAG

public static final int ISLAND_FLAG

Flags stored in flags Used when crawling contact graph when forming islands.

See Also:

• Constant Field Values

TOUCHING_FLAG

public static final int TOUCHING_FLAG

Set when the shapes are touching.

See Also:

• Constant Field Values

ENABLED_FLAG

public static final int ENABLED_FLAG

This contact can be disabled (by user)

See Also:

• Constant Field Values

FILTER_FLAG

public static final int FILTER_FLAG

This contact needs filtering because a fixture filter was changed.

See Also:

• Constant Field Values

BULLET_HIT_FLAG

public static final int BULLET_HIT_FLAG

This bullet contact had a TOI event

See Also:

• Constant Field Values

TOI_FLAG

public static final int TOI_FLAG

See Also:

• Constant Field Values

flags

public int flags

prev

public Contact prev

World pool and list pointers.

next

public Contact next

nodeA

public ContactEdge nodeA

Nodes for connecting bodies.

nodeB

public ContactEdge nodeB

fixtureA

public Fixture fixtureA

fixtureB

public Fixture fixtureB

indexA

public int indexA

indexB

public int indexB

manifold

public final Manifold manifold

toiCount

public float toiCount

toi

public float toi

friction

public float friction

restitution

public float restitution

tangentSpeed

public float tangentSpeed

pool

protected final WorldPool pool

Constructor Details

Contact

protected Contact(WorldPool argPool)

Method Details

init

public void init(Fixture fA,
 int indexA,
 Fixture fB,
 int indexB)

initialization for pooling

getManifold

public Manifold getManifold()

Get the contact manifold. Do not modify the manifold unless you understand the internals of JBox2D.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 92 - 95

getWorldManifold

public void getWorldManifold(WorldManifold worldManifold)

Get the world manifold.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 97 - 98

isTouching

public boolean isTouching()

Is this contact touching?

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 100 - 101

setEnabled

public void setEnabled(boolean flag)

Enable/disable this contact.

This can be used inside the pre-solve contact listener. The contact is only disabled for the current time step (or sub-step in continuous collisions).

Parameters:

flag - true if the contact should be enable else false.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 103 - 106

isEnabled

public boolean isEnabled()

Has this contact been disabled?

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 108 - 109

getNext

public Contact getNext()

Get the next contact in the world’s contact list.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 111 - 113

getFixtureA

public Fixture getFixtureA()

Get fixture A in this contact.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 115 - 117

getChildIndexA

public int getChildIndexA()

Get the child primitive index for fixture A.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 119 - 120

getFixtureB

public Fixture getFixtureB()

Get fixture B in this contact.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 122 - 124

getChildIndexB

public int getChildIndexB()

Get the child primitive index for fixture B.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 126 - 127

setFriction

public void setFriction(float friction)

Override the default friction mixture. You can call this in ContactListener.preSolve(Contact, Manifold). This value persists until set or reset.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 129 - 131

getFriction

public float getFriction()

Get the friction.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 133 - 134

resetFriction

public void resetFriction()

Reset the friction mixture to the default value.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 136 - 137

setRestitution

public void setRestitution(float restitution)

Override the default restitution mixture. You can call this in ContactListener.preSolve(Contact, Manifold). The value persists until you set or reset.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 139 - 141

getRestitution

public float getRestitution()

Get the restitution.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 143 - 144

resetRestitution

public void resetRestitution()

Reset the restitution to the default value.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 146 - 147

setTangentSpeed

public void setTangentSpeed(float speed)

Set the desired tangent speed for a conveyor belt behavior. In meters per second.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 159 - 160

getTangentSpeed

public float getTangentSpeed()

Get the desired tangent speed. In meters per second.

Returns:

the desired tangent speed. In meters per second.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 162 - 163

evaluate

public abstract void evaluate(Manifold manifold,
 Transform xfA,
 Transform xfB)

Evaluate this contact with your own manifold and transforms.

Repolink:

Github: erincatto/box2d include/box2d/b2_contact.h Lines 165 - 166

flagForFiltering

public void flagForFiltering()

Flag this contact for filtering. Filtering will occur the next time step.

update

public void update(ContactListener listener)

mixFriction

public static float mixFriction(float friction1,
 float friction2)

Friction mixing law. The idea is to allow either fixture to drive the restitution to zero. For example, anything slides on ice.

mixRestitution

public static float mixRestitution(float restitution1,
 float restitution2)

Restitution mixing law. The idea is allowed for anything to bounce off an inelastic surface. For example, a superball bounces on anything.