Module org.dyn4j

Package org.dyn4j.world

Class ConstraintGraph<T extends PhysicsBody>

Object

ConstraintGraph<T>

Type Parameters:

T - the PhysicsBody type

public final class ConstraintGraph<T extends PhysicsBody>
extends Object

Represents an undirected graph of constraints involving PhysicsBodys with the desire to split the simulation into smaller, solvable chunks.

The graph is maintained by using the various add/remove methods. The PhysicsWorld is a consumer of this object, adding nodes and edges when bodies/joints are added. During the collision detection process, contact edges are cleared and recreated.

Solving of the graph happens internally by performing depth-first traversal and the building of Islands separated by static PhysicsBodys.

Since:

4.0.0

Version:

4.0.0

Author:

William Bittle

Constructor Summary

Constructors

Constructor	Description
ConstraintGraph()	Minimal constructor.
ConstraintGraph(int initialBodyCount, int initialJointCount)	Full constructor.

Method Summary

Modifier and Type	Method	Description
void	addBody(T body)	Adds an interaction graph node for the given body.
void	addContactConstraint(ContactConstraint<T> contactConstraint)	Adds an interaction graph edge for the given ContactConstraint.
void	addJoint(Joint<T> joint)	Adds an interaction graph edge for the given Joint.
void	clear()	Clears the graph of all nodes and edges.
boolean	containsBody(T body)	Returns true if the given body is part of the interaction graph.
boolean	containsContactConstraint(ContactConstraint<T> contactConstraint)	Returns true if the given contact constraint exists in this interaction graph.
boolean	containsJoint(Joint<T> joint)	Returns true if the given joint exists in this interaction graph.
List<ContactConstraint<T>>	getContacts(T body)	Returns the ContactConstraints for the given PhysicsBody.
List<T>	getInContactBodies(T body, boolean includeSensedContact)	Returns a list of all PhysicsBodys that are in contact with the given PhysicsBody.
List<T>	getJoinedBodies(T body)	Returns the PhysicsBodys joined to the given PhysicsBody via Joints.
List<Joint<T>>	getJoints(T body)	Returns the Joints the given PhysicsBody is a member of.
ConstraintGraphNode<T>	getNode(T body)	Returns the node for the given body on the graph.
boolean	isInContact(T body1, T body2)	Returns true if the given PhysicsBodys are currently in collision.
boolean	isJoined(T body1, T body2)	Returns true if the two PhysicsBodys are joined via a Joint.
boolean	isJointCollisionAllowed(T body1, T body2)	Returns true if the two PhysicsBodys are joined by at least one Joint where the collision allowed property is true.
void	removeAllContactConstraints()	Removes all edges in the graph related to contact constraints.
void	removeAllJoints()	Removes all edges in the graph related to joints.
ConstraintGraphNode<T>	removeBody(T body)	Removes the given body from the graph.
void	removeContactConstraint(ContactConstraint<T> contactConstraint)	Removes the given contact constraint from the graph.
void	removeJoint(Joint<T> joint)	Removes the given joint from the graph.
int	size()	Returns the number of nodes in the graph.
void	solve(ContactConstraintSolver<T> solver, Vector2 gravity, TimeStep step, Settings settings)	Solves the interation graph constraints (Joints/Contacts) by splitting the graph into Islands.

Methods inherited from class Object

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

Constructor Detail

ConstraintGraph

public ConstraintGraph()

Minimal constructor.

ConstraintGraph

public ConstraintGraph(int initialBodyCount,
                       int initialJointCount)

Full constructor.

Parameters:

initialBodyCount - the initial body count

initialJointCount - the initial joint count

Method Detail

addBody

public void addBody(T body)

Adds an interaction graph node for the given body.

Parameters:

body - the body

addContactConstraint

public void addContactConstraint(ContactConstraint<T> contactConstraint)

Adds an interaction graph edge for the given ContactConstraint.

Parameters:

contactConstraint - the contact constraint

addJoint

public void addJoint(Joint<T> joint)

Adds an interaction graph edge for the given Joint.

Parameters:

joint - the joint

containsBody

public boolean containsBody(T body)

Returns true if the given body is part of the interaction graph.

Parameters:

body - the body

Returns:

boolean

removeBody

public ConstraintGraphNode<T> removeBody(T body)

Removes the given body from the graph.

A body represents a node in the graph, therefore removing the node will remove the edges between the given node and other nodes as well.

Parameters:

body - the body to remove

Returns:

ConstraintGraphNode<T>

containsJoint

public boolean containsJoint(Joint<T> joint)

Returns true if the given joint exists in this interaction graph.

Parameters:

joint - the joint

Returns:

boolean

containsContactConstraint

public boolean containsContactConstraint(ContactConstraint<T> contactConstraint)

Returns true if the given contact constraint exists in this interaction graph.

Parameters:

contactConstraint - the contact constraint

Returns:

boolean

removeJoint

public void removeJoint(Joint<T> joint)

Removes the given joint from the graph.

A joint is an edge connecting body nodes. This method removes the edges related to the given joint.

Parameters:

joint - the joint to remove

removeContactConstraint

public void removeContactConstraint(ContactConstraint<T> contactConstraint)

Removes the given contact constraint from the graph.

A contact constraint is an edge connecting body nodes. This method removes the edges related to the given contact constraint.

Parameters:

contactConstraint - the contact constraint to remove

getNode

public ConstraintGraphNode<T> getNode(T body)

Returns the node for the given body on the graph.

Returns null if the body is not on the graph.

Parameters:

body - the body to remove

Returns:

ConstraintGraphNode<T>

removeAllContactConstraints

public void removeAllContactConstraints()

Removes all edges in the graph related to contact constraints.

removeAllJoints

public void removeAllJoints()

Removes all edges in the graph related to joints.

clear

public void clear()

Clears the graph of all nodes and edges.

size

public int size()

Returns the number of nodes in the graph.

Returns:

int

isInContact

public boolean isInContact(T body1,
                           T body2)

Returns true if the given PhysicsBodys are currently in collision.

Collision is defined as the two bodies interacting to the level of ContactConstraint generation and solving.

Parameters:

body1 - the first body

body2 - the second body

Returns:

boolean

getContacts

public List<ContactConstraint<T>> getContacts(T body)

Returns the ContactConstraints for the given PhysicsBody.

These represent the contact pairs between the given body and the others it's colliding with. Each ContactConstraint could have 1 or 2 contacts associated with it.

Parameters:

body - the body

Returns:

List<ContactConstraint>

getInContactBodies

public List<T> getInContactBodies(T body,
                                  boolean includeSensedContact)

Returns a list of all PhysicsBodys that are in contact with the given PhysicsBody.

Parameters:

body - the body

includeSensedContact - true if sensed contacts should be included in the results

Returns:

List<PhysicsBody>

isJointCollisionAllowed

public boolean isJointCollisionAllowed(T body1,
                                       T body2)

Returns true if the two PhysicsBodys are joined by at least one Joint where the collision allowed property is true.

Parameters:

body1 - the first body

body2 - the second body

Returns:

boolean

isJoined

public boolean isJoined(T body1,
                        T body2)

Returns true if the two PhysicsBodys are joined via a Joint.

Parameters:

body1 - the first body

body2 - the second body

Returns:

boolean

getJoints

public List<Joint<T>> getJoints(T body)

Returns the Joints the given PhysicsBody is a member of.

Parameters:

body - the body

Returns:

List<Joint>

getJoinedBodies

public List<T> getJoinedBodies(T body)

Returns the PhysicsBodys joined to the given PhysicsBody via Joints.

Parameters:

body - the body

Returns:

List<PhysicsBody>

solve

public void solve(ContactConstraintSolver<T> solver,
                  Vector2 gravity,
                  TimeStep step,
                  Settings settings)

Solves the interation graph constraints (Joints/Contacts) by splitting the graph into Islands. Each Island represents a segment of the constraint graph that can be solved in isolation.

Parameters:

solver - the contact constraint solver

gravity - the world gravity

step - the time step information

settings - the settings