Box2D 2.3.0 A 2D Physics Engine for Games

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b2DynamicTree Class Reference

`#include <b2DynamicTree.h>`

## Public Member Functions
| b2DynamicTree ()
| Constructing the tree initializes the node pool.
| ~b2DynamicTree ()
| Destroy the tree, freeing the node pool.
int32 | CreateProxy (const b2AABB &aabb, void *userData)
| Create a proxy. Provide a tight fitting AABB and a userData pointer.
void | DestroyProxy (int32 proxyId)
| Destroy a proxy. This asserts if the id is invalid.
bool | MoveProxy (int32 proxyId, const b2AABB &aabb1, const b2Vec2 &displacement)
void * | GetUserData (int32 proxyId) const
const b2AABB & | GetFatAABB (int32 proxyId) const
| Get the fat AABB for a proxy.
template<typename T >
void | Query (T *callback, const b2AABB &aabb) const
template<typename T >
void | RayCast (T *callback, const b2RayCastInput &input) const
void | Validate () const
| Validate this tree. For testing.
int32 | GetHeight () const
int32 | GetMaxBalance () const
float32 | GetAreaRatio () const
| Get the ratio of the sum of the node areas to the root area.
void | RebuildBottomUp ()
| Build an optimal tree. Very expensive. For testing.
void | ShiftOrigin (const b2Vec2 &newOrigin)

## Detailed Description

A dynamic AABB tree broad-phase, inspired by Nathanael Presson's btDbvt. 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 b2_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.

Nodes are pooled and relocatable, so we use node indices rather than pointers.

## Member Function Documentation

int32 b2DynamicTree::GetHeight | ( |  | ) | const

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

int32 b2DynamicTree::GetMaxBalance | ( |  | ) | const

Get the maximum balance of an node in the tree. The balance is the difference in height of the two children of a node.

void * b2DynamicTree::GetUserData | ( | int32 | proxyId | ) | const
| inline

Get proxy user data.

Returns
  the proxy user data or 0 if the id is invalid.

bool b2DynamicTree::MoveProxy | ( | int32 | proxyId,
|  | const b2AABB & | aabb1,
|  | const b2Vec2 & | 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.

template<typename T >

void b2DynamicTree::Query | ( | T * | callback,
|  | const b2AABB & | aabb
| ) |  | const
| inline

Query an AABB for overlapping proxies. The callback class is called for each proxy that overlaps the supplied AABB.

template<typename T >

void b2DynamicTree::RayCast | ( | T * | callback,
|  | const b2RayCastInput & | input
| ) |  | const
| inline

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.

void b2DynamicTree::ShiftOrigin | ( | const b2Vec2 & | newOrigin | ) |

Shift the world origin. Useful for large worlds. The shift formula is: position -= newOrigin

Parameters

  newOrigin | the new origin with respect to the old origin

The documentation for this class was generated from the following files:

- b2DynamicTree.h
- b2DynamicTree.cpp