org.jbox2d.collision.broadphase
Class DynamicTree

java.lang.Object
  extended by org.jbox2d.collision.broadphase.DynamicTree

public class DynamicTree
extends java.lang.Object

A dynamic tree arranges data in a binary tree to accelerate queries such as volume queries and ray casts. Leafs are proxies with an AABB. In the tree we expand the proxy AABB by _fatAABBFactor so that the proxy AABB is bigger than the client object. This allows the client object to move by small amounts without triggering a tree update.

Author:
daniel

Field Summary
static int MAX_STACK_SIZE
           
 
Constructor Summary
DynamicTree()
           
 
Method Summary
 int computeHeight()
          Compute the height of the tree.
 int createProxy(AABB aabb, java.lang.Object userData)
          Create a proxy.
 void destroyProxy(int proxyId)
          Destroy a proxy
 void drawTree(DebugDraw argDraw)
           
 void drawTree(DebugDraw argDraw, int nodeId, int spot, int height)
           
 float getAreaRatio()
          Get the ratio of the sum of the node areas to the root area.
 AABB getFatAABB(int proxyId)
           
 int getHeight()
          Compute the height of the binary tree in O(N) time.
 int getInsertionCount()
           
 int getMaxBalance()
          Get the maximum balance of an node in the tree.
 java.lang.Object getUserData(int proxyId)
           
 boolean moveProxy(int proxyId, AABB aabb, Vec2 displacement)
          Move a proxy with a swepted AABB.
 void query(TreeCallback callback, AABB aabb)
          Query an AABB for overlapping proxies.
 void raycast(TreeRayCastCallback callback, RayCastInput input)
          Ray-cast against the proxies in the tree.
 void rebuildBottomUp()
          Build an optimal tree.
 void validate()
          Validate this tree.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

MAX_STACK_SIZE

public static final int MAX_STACK_SIZE
See Also:
Constant Field Values
Constructor Detail

DynamicTree

public DynamicTree()
Method Detail

createProxy

public final int createProxy(AABB aabb,
                             java.lang.Object userData)
Create a proxy. Provide a tight fitting AABB and a userData pointer.

Parameters:
aabb -
userData -
Returns:

destroyProxy

public final void destroyProxy(int proxyId)
Destroy a proxy

Parameters:
proxyId -

moveProxy

public final boolean moveProxy(int proxyId,
                               AABB aabb,
                               Vec2 displacement)
Move a proxy with a swepted AABB. If the proxy has moved outside of its fattened AABB, then the proxy is removed from the tree and re-inserted. Otherwise the function returns immediately.

Returns:
true if the proxy was re-inserted.

getUserData

public final java.lang.Object getUserData(int proxyId)

getFatAABB

public final AABB getFatAABB(int proxyId)

query

public final void query(TreeCallback callback,
                        AABB aabb)
Query an AABB for overlapping proxies. The callback class is called for each proxy that overlaps the supplied AABB.

Parameters:
callback -
araabbgAABB -

raycast

public void raycast(TreeRayCastCallback callback,
                    RayCastInput input)
Ray-cast against the proxies in the tree. This relies on the callback to perform a exact ray-cast in the case were the proxy contains a shape. The callback also performs the any collision filtering. This has performance roughly equal to k * log(n), where k is the number of collisions and n is the number of proxies in the tree.

Parameters:
input - the ray-cast input data. The ray extends from p1 to p1 + maxFraction * (p2 - p1).
callback - a callback class that is called for each proxy that is hit by the ray.

computeHeight

public final int computeHeight()
Compute the height of the tree.


validate

public void validate()
Validate this tree. For testing.


getHeight

public int getHeight()
Compute the height of the binary tree in O(N) time. Should not be called often.

Returns:

getMaxBalance

public int getMaxBalance()
Get the maximum balance of an node in the tree. The balance is the difference in height of the two children of a node.

Returns:

getAreaRatio

public float getAreaRatio()
Get the ratio of the sum of the node areas to the root area.

Returns:

rebuildBottomUp

public void rebuildBottomUp()
Build an optimal tree. Very expensive. For testing.


getInsertionCount

public int getInsertionCount()

drawTree

public void drawTree(DebugDraw argDraw)

drawTree

public void drawTree(DebugDraw argDraw,
                     int nodeId,
                     int spot,
                     int height)


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