781 lines
		
	
	
		
			16 KiB
		
	
	
	
		
			C++
		
	
	
	
			
		
		
	
	
			781 lines
		
	
	
		
			16 KiB
		
	
	
	
		
			C++
		
	
	
	
| /*
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| * Copyright (c) 2009 Erin Catto http://www.box2d.org
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| *
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| * This software is provided 'as-is', without any express or implied
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| * warranty.  In no event will the authors be held liable for any damages
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| * arising from the use of this software.
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| * Permission is granted to anyone to use this software for any purpose,
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| * including commercial applications, and to alter it and redistribute it
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| * freely, subject to the following restrictions:
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| * 1. The origin of this software must not be misrepresented; you must not
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| * claim that you wrote the original software. If you use this software
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| * in a product, an acknowledgment in the product documentation would be
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| * appreciated but is not required.
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| * 2. Altered source versions must be plainly marked as such, and must not be
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| * misrepresented as being the original software.
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| * 3. This notice may not be removed or altered from any source distribution.
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| */
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| 
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| #include "Box2D/Collision/b2DynamicTree.h"
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| #include <string.h>
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| 
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| b2DynamicTree::b2DynamicTree()
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| {
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| 	m_root = b2_nullNode;
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| 
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| 	m_nodeCapacity = 16;
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| 	m_nodeCount = 0;
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| 	m_nodes = (b2TreeNode*)b2Alloc(m_nodeCapacity * sizeof(b2TreeNode));
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| 	memset(m_nodes, 0, m_nodeCapacity * sizeof(b2TreeNode));
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| 
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| 	// Build a linked list for the free list.
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| 	for (int32 i = 0; i < m_nodeCapacity - 1; ++i)
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| 	{
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| 		m_nodes[i].next = i + 1;
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| 		m_nodes[i].height = -1;
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| 	}
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| 	m_nodes[m_nodeCapacity-1].next = b2_nullNode;
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| 	m_nodes[m_nodeCapacity-1].height = -1;
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| 	m_freeList = 0;
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| 
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| 	m_path = 0;
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| 
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| 	m_insertionCount = 0;
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| }
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| 
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| b2DynamicTree::~b2DynamicTree()
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| {
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| 	// This frees the entire tree in one shot.
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| 	b2Free(m_nodes);
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| }
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| 
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| // Allocate a node from the pool. Grow the pool if necessary.
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| int32 b2DynamicTree::AllocateNode()
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| {
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| 	// Expand the node pool as needed.
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| 	if (m_freeList == b2_nullNode)
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| 	{
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| 		b2Assert(m_nodeCount == m_nodeCapacity);
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| 
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| 		// The free list is empty. Rebuild a bigger pool.
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| 		b2TreeNode* oldNodes = m_nodes;
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| 		m_nodeCapacity *= 2;
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| 		m_nodes = (b2TreeNode*)b2Alloc(m_nodeCapacity * sizeof(b2TreeNode));
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| 		memcpy(m_nodes, oldNodes, m_nodeCount * sizeof(b2TreeNode));
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| 		b2Free(oldNodes);
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| 
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| 		// Build a linked list for the free list. The parent
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| 		// pointer becomes the "next" pointer.
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| 		for (int32 i = m_nodeCount; i < m_nodeCapacity - 1; ++i)
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| 		{
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| 			m_nodes[i].next = i + 1;
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| 			m_nodes[i].height = -1;
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| 		}
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| 		m_nodes[m_nodeCapacity-1].next = b2_nullNode;
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| 		m_nodes[m_nodeCapacity-1].height = -1;
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| 		m_freeList = m_nodeCount;
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| 	}
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| 
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| 	// Peel a node off the free list.
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| 	int32 nodeId = m_freeList;
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| 	m_freeList = m_nodes[nodeId].next;
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| 	m_nodes[nodeId].parent = b2_nullNode;
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| 	m_nodes[nodeId].child1 = b2_nullNode;
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| 	m_nodes[nodeId].child2 = b2_nullNode;
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| 	m_nodes[nodeId].height = 0;
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| 	m_nodes[nodeId].userData = nullptr;
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| 	++m_nodeCount;
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| 	return nodeId;
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| }
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| 
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| // Return a node to the pool.
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| void b2DynamicTree::FreeNode(int32 nodeId)
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| {
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| 	b2Assert(0 <= nodeId && nodeId < m_nodeCapacity);
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| 	b2Assert(0 < m_nodeCount);
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| 	m_nodes[nodeId].next = m_freeList;
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| 	m_nodes[nodeId].height = -1;
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| 	m_freeList = nodeId;
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| 	--m_nodeCount;
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| }
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| 
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| // Create a proxy in the tree as a leaf node. We return the index
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| // of the node instead of a pointer so that we can grow
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| // the node pool.
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| int32 b2DynamicTree::CreateProxy(const b2AABB& aabb, void* userData)
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| {
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| 	int32 proxyId = AllocateNode();
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| 
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| 	// Fatten the aabb.
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| 	b2Vec2 r(b2_aabbExtension, b2_aabbExtension);
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| 	m_nodes[proxyId].aabb.lowerBound = aabb.lowerBound - r;
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| 	m_nodes[proxyId].aabb.upperBound = aabb.upperBound + r;
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| 	m_nodes[proxyId].userData = userData;
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| 	m_nodes[proxyId].height = 0;
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| 
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| 	InsertLeaf(proxyId);
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| 
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| 	return proxyId;
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| }
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| 
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| void b2DynamicTree::DestroyProxy(int32 proxyId)
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| {
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| 	b2Assert(0 <= proxyId && proxyId < m_nodeCapacity);
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| 	b2Assert(m_nodes[proxyId].IsLeaf());
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| 
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| 	RemoveLeaf(proxyId);
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| 	FreeNode(proxyId);
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| }
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| 
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| bool b2DynamicTree::MoveProxy(int32 proxyId, const b2AABB& aabb, const b2Vec2& displacement)
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| {
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| 	b2Assert(0 <= proxyId && proxyId < m_nodeCapacity);
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| 
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| 	b2Assert(m_nodes[proxyId].IsLeaf());
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| 
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| 	if (m_nodes[proxyId].aabb.Contains(aabb))
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| 	{
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| 		return false;
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| 	}
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| 
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| 	RemoveLeaf(proxyId);
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| 
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| 	// Extend AABB.
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| 	b2AABB b = aabb;
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| 	b2Vec2 r(b2_aabbExtension, b2_aabbExtension);
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| 	b.lowerBound = b.lowerBound - r;
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| 	b.upperBound = b.upperBound + r;
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| 
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| 	// Predict AABB displacement.
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| 	b2Vec2 d = b2_aabbMultiplier * displacement;
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| 
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| 	if (d.x < 0.0f)
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| 	{
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| 		b.lowerBound.x += d.x;
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| 	}
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| 	else
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| 	{
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| 		b.upperBound.x += d.x;
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| 	}
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| 
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| 	if (d.y < 0.0f)
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| 	{
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| 		b.lowerBound.y += d.y;
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| 	}
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| 	else
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| 	{
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| 		b.upperBound.y += d.y;
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| 	}
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| 
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| 	m_nodes[proxyId].aabb = b;
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| 
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| 	InsertLeaf(proxyId);
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| 	return true;
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| }
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| 
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| void b2DynamicTree::InsertLeaf(int32 leaf)
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| {
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| 	++m_insertionCount;
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| 
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| 	if (m_root == b2_nullNode)
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| 	{
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| 		m_root = leaf;
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| 		m_nodes[m_root].parent = b2_nullNode;
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| 		return;
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| 	}
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| 
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| 	// Find the best sibling for this node
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| 	b2AABB leafAABB = m_nodes[leaf].aabb;
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| 	int32 index = m_root;
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| 	while (m_nodes[index].IsLeaf() == false)
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| 	{
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| 		int32 child1 = m_nodes[index].child1;
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| 		int32 child2 = m_nodes[index].child2;
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| 
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| 		float32 area = m_nodes[index].aabb.GetPerimeter();
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| 
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| 		b2AABB combinedAABB;
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| 		combinedAABB.Combine(m_nodes[index].aabb, leafAABB);
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| 		float32 combinedArea = combinedAABB.GetPerimeter();
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| 
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| 		// Cost of creating a new parent for this node and the new leaf
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| 		float32 cost = 2.0f * combinedArea;
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| 
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| 		// Minimum cost of pushing the leaf further down the tree
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| 		float32 inheritanceCost = 2.0f * (combinedArea - area);
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| 
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| 		// Cost of descending into child1
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| 		float32 cost1;
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| 		if (m_nodes[child1].IsLeaf())
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| 		{
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| 			b2AABB aabb;
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| 			aabb.Combine(leafAABB, m_nodes[child1].aabb);
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| 			cost1 = aabb.GetPerimeter() + inheritanceCost;
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| 		}
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| 		else
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| 		{
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| 			b2AABB aabb;
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| 			aabb.Combine(leafAABB, m_nodes[child1].aabb);
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| 			float32 oldArea = m_nodes[child1].aabb.GetPerimeter();
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| 			float32 newArea = aabb.GetPerimeter();
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| 			cost1 = (newArea - oldArea) + inheritanceCost;
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| 		}
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| 
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| 		// Cost of descending into child2
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| 		float32 cost2;
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| 		if (m_nodes[child2].IsLeaf())
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| 		{
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| 			b2AABB aabb;
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| 			aabb.Combine(leafAABB, m_nodes[child2].aabb);
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| 			cost2 = aabb.GetPerimeter() + inheritanceCost;
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| 		}
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| 		else
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| 		{
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| 			b2AABB aabb;
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| 			aabb.Combine(leafAABB, m_nodes[child2].aabb);
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| 			float32 oldArea = m_nodes[child2].aabb.GetPerimeter();
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| 			float32 newArea = aabb.GetPerimeter();
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| 			cost2 = newArea - oldArea + inheritanceCost;
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| 		}
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| 
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| 		// Descend according to the minimum cost.
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| 		if (cost < cost1 && cost < cost2)
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| 		{
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| 			break;
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| 		}
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| 
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| 		// Descend
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| 		if (cost1 < cost2)
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| 		{
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| 			index = child1;
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| 		}
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| 		else
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| 		{
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| 			index = child2;
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| 		}
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| 	}
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| 
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| 	int32 sibling = index;
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| 
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| 	// Create a new parent.
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| 	int32 oldParent = m_nodes[sibling].parent;
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| 	int32 newParent = AllocateNode();
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| 	m_nodes[newParent].parent = oldParent;
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| 	m_nodes[newParent].userData = nullptr;
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| 	m_nodes[newParent].aabb.Combine(leafAABB, m_nodes[sibling].aabb);
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| 	m_nodes[newParent].height = m_nodes[sibling].height + 1;
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| 
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| 	if (oldParent != b2_nullNode)
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| 	{
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| 		// The sibling was not the root.
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| 		if (m_nodes[oldParent].child1 == sibling)
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| 		{
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| 			m_nodes[oldParent].child1 = newParent;
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| 		}
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| 		else
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| 		{
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| 			m_nodes[oldParent].child2 = newParent;
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| 		}
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| 
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| 		m_nodes[newParent].child1 = sibling;
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| 		m_nodes[newParent].child2 = leaf;
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| 		m_nodes[sibling].parent = newParent;
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| 		m_nodes[leaf].parent = newParent;
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| 	}
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| 	else
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| 	{
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| 		// The sibling was the root.
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| 		m_nodes[newParent].child1 = sibling;
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| 		m_nodes[newParent].child2 = leaf;
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| 		m_nodes[sibling].parent = newParent;
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| 		m_nodes[leaf].parent = newParent;
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| 		m_root = newParent;
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| 	}
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| 
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| 	// Walk back up the tree fixing heights and AABBs
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| 	index = m_nodes[leaf].parent;
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| 	while (index != b2_nullNode)
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| 	{
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| 		index = Balance(index);
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| 
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| 		int32 child1 = m_nodes[index].child1;
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| 		int32 child2 = m_nodes[index].child2;
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| 
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| 		b2Assert(child1 != b2_nullNode);
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| 		b2Assert(child2 != b2_nullNode);
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| 
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| 		m_nodes[index].height = 1 + b2Max(m_nodes[child1].height, m_nodes[child2].height);
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| 		m_nodes[index].aabb.Combine(m_nodes[child1].aabb, m_nodes[child2].aabb);
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| 
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| 		index = m_nodes[index].parent;
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| 	}
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| 
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| 	//Validate();
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| }
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| 
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| void b2DynamicTree::RemoveLeaf(int32 leaf)
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| {
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| 	if (leaf == m_root)
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| 	{
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| 		m_root = b2_nullNode;
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| 		return;
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| 	}
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| 
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| 	int32 parent = m_nodes[leaf].parent;
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| 	int32 grandParent = m_nodes[parent].parent;
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| 	int32 sibling;
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| 	if (m_nodes[parent].child1 == leaf)
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| 	{
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| 		sibling = m_nodes[parent].child2;
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| 	}
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| 	else
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| 	{
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| 		sibling = m_nodes[parent].child1;
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| 	}
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| 
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| 	if (grandParent != b2_nullNode)
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| 	{
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| 		// Destroy parent and connect sibling to grandParent.
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| 		if (m_nodes[grandParent].child1 == parent)
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| 		{
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| 			m_nodes[grandParent].child1 = sibling;
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| 		}
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| 		else
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| 		{
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| 			m_nodes[grandParent].child2 = sibling;
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| 		}
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| 		m_nodes[sibling].parent = grandParent;
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| 		FreeNode(parent);
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| 
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| 		// Adjust ancestor bounds.
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| 		int32 index = grandParent;
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| 		while (index != b2_nullNode)
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| 		{
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| 			index = Balance(index);
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| 
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| 			int32 child1 = m_nodes[index].child1;
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| 			int32 child2 = m_nodes[index].child2;
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| 
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| 			m_nodes[index].aabb.Combine(m_nodes[child1].aabb, m_nodes[child2].aabb);
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| 			m_nodes[index].height = 1 + b2Max(m_nodes[child1].height, m_nodes[child2].height);
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| 
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| 			index = m_nodes[index].parent;
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| 		}
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| 	}
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| 	else
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| 	{
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| 		m_root = sibling;
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| 		m_nodes[sibling].parent = b2_nullNode;
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| 		FreeNode(parent);
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| 	}
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| 
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| 	//Validate();
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| }
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| 
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| // Perform a left or right rotation if node A is imbalanced.
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| // Returns the new root index.
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| int32 b2DynamicTree::Balance(int32 iA)
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| {
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| 	b2Assert(iA != b2_nullNode);
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| 
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| 	b2TreeNode* A = m_nodes + iA;
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| 	if (A->IsLeaf() || A->height < 2)
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| 	{
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| 		return iA;
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| 	}
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| 
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| 	int32 iB = A->child1;
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| 	int32 iC = A->child2;
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| 	b2Assert(0 <= iB && iB < m_nodeCapacity);
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| 	b2Assert(0 <= iC && iC < m_nodeCapacity);
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| 
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| 	b2TreeNode* B = m_nodes + iB;
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| 	b2TreeNode* C = m_nodes + iC;
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| 
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| 	int32 balance = C->height - B->height;
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| 
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| 	// Rotate C up
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| 	if (balance > 1)
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| 	{
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| 		int32 iF = C->child1;
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| 		int32 iG = C->child2;
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| 		b2TreeNode* F = m_nodes + iF;
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| 		b2TreeNode* G = m_nodes + iG;
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| 		b2Assert(0 <= iF && iF < m_nodeCapacity);
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| 		b2Assert(0 <= iG && iG < m_nodeCapacity);
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| 
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| 		// Swap A and C
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| 		C->child1 = iA;
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| 		C->parent = A->parent;
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| 		A->parent = iC;
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| 
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| 		// A's old parent should point to C
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| 		if (C->parent != b2_nullNode)
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| 		{
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| 			if (m_nodes[C->parent].child1 == iA)
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| 			{
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| 				m_nodes[C->parent].child1 = iC;
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| 			}
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| 			else
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| 			{
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| 				b2Assert(m_nodes[C->parent].child2 == iA);
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| 				m_nodes[C->parent].child2 = iC;
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| 			}
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| 		}
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| 		else
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| 		{
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| 			m_root = iC;
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| 		}
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| 
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| 		// Rotate
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| 		if (F->height > G->height)
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| 		{
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| 			C->child2 = iF;
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| 			A->child2 = iG;
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| 			G->parent = iA;
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| 			A->aabb.Combine(B->aabb, G->aabb);
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| 			C->aabb.Combine(A->aabb, F->aabb);
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| 
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| 			A->height = 1 + b2Max(B->height, G->height);
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| 			C->height = 1 + b2Max(A->height, F->height);
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| 		}
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| 		else
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| 		{
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| 			C->child2 = iG;
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| 			A->child2 = iF;
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| 			F->parent = iA;
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| 			A->aabb.Combine(B->aabb, F->aabb);
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| 			C->aabb.Combine(A->aabb, G->aabb);
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| 
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| 			A->height = 1 + b2Max(B->height, F->height);
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| 			C->height = 1 + b2Max(A->height, G->height);
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| 		}
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| 
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| 		return iC;
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| 	}
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| 	
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| 	// Rotate B up
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| 	if (balance < -1)
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| 	{
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| 		int32 iD = B->child1;
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| 		int32 iE = B->child2;
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| 		b2TreeNode* D = m_nodes + iD;
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| 		b2TreeNode* E = m_nodes + iE;
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| 		b2Assert(0 <= iD && iD < m_nodeCapacity);
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| 		b2Assert(0 <= iE && iE < m_nodeCapacity);
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| 
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| 		// Swap A and B
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| 		B->child1 = iA;
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| 		B->parent = A->parent;
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| 		A->parent = iB;
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| 
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| 		// A's old parent should point to B
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| 		if (B->parent != b2_nullNode)
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| 		{
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| 			if (m_nodes[B->parent].child1 == iA)
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| 			{
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| 				m_nodes[B->parent].child1 = iB;
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| 			}
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| 			else
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| 			{
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| 				b2Assert(m_nodes[B->parent].child2 == iA);
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| 				m_nodes[B->parent].child2 = iB;
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| 			}
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| 		}
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| 		else
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| 		{
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| 			m_root = iB;
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| 		}
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| 
 | |
| 		// Rotate
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| 		if (D->height > E->height)
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| 		{
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| 			B->child2 = iD;
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| 			A->child1 = iE;
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| 			E->parent = iA;
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| 			A->aabb.Combine(C->aabb, E->aabb);
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| 			B->aabb.Combine(A->aabb, D->aabb);
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| 
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| 			A->height = 1 + b2Max(C->height, E->height);
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| 			B->height = 1 + b2Max(A->height, D->height);
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| 		}
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| 		else
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| 		{
 | |
| 			B->child2 = iE;
 | |
| 			A->child1 = iD;
 | |
| 			D->parent = iA;
 | |
| 			A->aabb.Combine(C->aabb, D->aabb);
 | |
| 			B->aabb.Combine(A->aabb, E->aabb);
 | |
| 
 | |
| 			A->height = 1 + b2Max(C->height, D->height);
 | |
| 			B->height = 1 + b2Max(A->height, E->height);
 | |
| 		}
 | |
| 
 | |
| 		return iB;
 | |
| 	}
 | |
| 
 | |
| 	return iA;
 | |
| }
 | |
| 
 | |
| int32 b2DynamicTree::GetHeight() const
 | |
| {
 | |
| 	if (m_root == b2_nullNode)
 | |
| 	{
 | |
| 		return 0;
 | |
| 	}
 | |
| 
 | |
| 	return m_nodes[m_root].height;
 | |
| }
 | |
| 
 | |
| //
 | |
| float32 b2DynamicTree::GetAreaRatio() const
 | |
| {
 | |
| 	if (m_root == b2_nullNode)
 | |
| 	{
 | |
| 		return 0.0f;
 | |
| 	}
 | |
| 
 | |
| 	const b2TreeNode* root = m_nodes + m_root;
 | |
| 	float32 rootArea = root->aabb.GetPerimeter();
 | |
| 
 | |
| 	float32 totalArea = 0.0f;
 | |
| 	for (int32 i = 0; i < m_nodeCapacity; ++i)
 | |
| 	{
 | |
| 		const b2TreeNode* node = m_nodes + i;
 | |
| 		if (node->height < 0)
 | |
| 		{
 | |
| 			// Free node in pool
 | |
| 			continue;
 | |
| 		}
 | |
| 
 | |
| 		totalArea += node->aabb.GetPerimeter();
 | |
| 	}
 | |
| 
 | |
| 	return totalArea / rootArea;
 | |
| }
 | |
| 
 | |
| // Compute the height of a sub-tree.
 | |
| int32 b2DynamicTree::ComputeHeight(int32 nodeId) const
 | |
| {
 | |
| 	b2Assert(0 <= nodeId && nodeId < m_nodeCapacity);
 | |
| 	b2TreeNode* node = m_nodes + nodeId;
 | |
| 
 | |
| 	if (node->IsLeaf())
 | |
| 	{
 | |
| 		return 0;
 | |
| 	}
 | |
| 
 | |
| 	int32 height1 = ComputeHeight(node->child1);
 | |
| 	int32 height2 = ComputeHeight(node->child2);
 | |
| 	return 1 + b2Max(height1, height2);
 | |
| }
 | |
| 
 | |
| int32 b2DynamicTree::ComputeHeight() const
 | |
| {
 | |
| 	int32 height = ComputeHeight(m_root);
 | |
| 	return height;
 | |
| }
 | |
| 
 | |
| void b2DynamicTree::ValidateStructure(int32 index) const
 | |
| {
 | |
| 	if (index == b2_nullNode)
 | |
| 	{
 | |
| 		return;
 | |
| 	}
 | |
| 
 | |
| 	if (index == m_root)
 | |
| 	{
 | |
| 		b2Assert(m_nodes[index].parent == b2_nullNode);
 | |
| 	}
 | |
| 
 | |
| 	const b2TreeNode* node = m_nodes + index;
 | |
| 
 | |
| 	int32 child1 = node->child1;
 | |
| 	int32 child2 = node->child2;
 | |
| 
 | |
| 	if (node->IsLeaf())
 | |
| 	{
 | |
| 		b2Assert(child1 == b2_nullNode);
 | |
| 		b2Assert(child2 == b2_nullNode);
 | |
| 		b2Assert(node->height == 0);
 | |
| 		return;
 | |
| 	}
 | |
| 
 | |
| 	b2Assert(0 <= child1 && child1 < m_nodeCapacity);
 | |
| 	b2Assert(0 <= child2 && child2 < m_nodeCapacity);
 | |
| 
 | |
| 	b2Assert(m_nodes[child1].parent == index);
 | |
| 	b2Assert(m_nodes[child2].parent == index);
 | |
| 
 | |
| 	ValidateStructure(child1);
 | |
| 	ValidateStructure(child2);
 | |
| }
 | |
| 
 | |
| void b2DynamicTree::ValidateMetrics(int32 index) const
 | |
| {
 | |
| 	if (index == b2_nullNode)
 | |
| 	{
 | |
| 		return;
 | |
| 	}
 | |
| 
 | |
| 	const b2TreeNode* node = m_nodes + index;
 | |
| 
 | |
| 	int32 child1 = node->child1;
 | |
| 	int32 child2 = node->child2;
 | |
| 
 | |
| 	if (node->IsLeaf())
 | |
| 	{
 | |
| 		b2Assert(child1 == b2_nullNode);
 | |
| 		b2Assert(child2 == b2_nullNode);
 | |
| 		b2Assert(node->height == 0);
 | |
| 		return;
 | |
| 	}
 | |
| 
 | |
| 	b2Assert(0 <= child1 && child1 < m_nodeCapacity);
 | |
| 	b2Assert(0 <= child2 && child2 < m_nodeCapacity);
 | |
| 
 | |
| 	int32 height1 = m_nodes[child1].height;
 | |
| 	int32 height2 = m_nodes[child2].height;
 | |
| 	int32 height;
 | |
| 	height = 1 + b2Max(height1, height2);
 | |
| 	b2Assert(node->height == height);
 | |
| 
 | |
| 	b2AABB aabb;
 | |
| 	aabb.Combine(m_nodes[child1].aabb, m_nodes[child2].aabb);
 | |
| 
 | |
| 	b2Assert(aabb.lowerBound == node->aabb.lowerBound);
 | |
| 	b2Assert(aabb.upperBound == node->aabb.upperBound);
 | |
| 
 | |
| 	ValidateMetrics(child1);
 | |
| 	ValidateMetrics(child2);
 | |
| }
 | |
| 
 | |
| void b2DynamicTree::Validate() const
 | |
| {
 | |
| #if defined(b2DEBUG)
 | |
| 	ValidateStructure(m_root);
 | |
| 	ValidateMetrics(m_root);
 | |
| 
 | |
| 	int32 freeCount = 0;
 | |
| 	int32 freeIndex = m_freeList;
 | |
| 	while (freeIndex != b2_nullNode)
 | |
| 	{
 | |
| 		b2Assert(0 <= freeIndex && freeIndex < m_nodeCapacity);
 | |
| 		freeIndex = m_nodes[freeIndex].next;
 | |
| 		++freeCount;
 | |
| 	}
 | |
| 
 | |
| 	b2Assert(GetHeight() == ComputeHeight());
 | |
| 
 | |
| 	b2Assert(m_nodeCount + freeCount == m_nodeCapacity);
 | |
| #endif
 | |
| }
 | |
| 
 | |
| int32 b2DynamicTree::GetMaxBalance() const
 | |
| {
 | |
| 	int32 maxBalance = 0;
 | |
| 	for (int32 i = 0; i < m_nodeCapacity; ++i)
 | |
| 	{
 | |
| 		const b2TreeNode* node = m_nodes + i;
 | |
| 		if (node->height <= 1)
 | |
| 		{
 | |
| 			continue;
 | |
| 		}
 | |
| 
 | |
| 		b2Assert(node->IsLeaf() == false);
 | |
| 
 | |
| 		int32 child1 = node->child1;
 | |
| 		int32 child2 = node->child2;
 | |
| 		int32 balance = b2Abs(m_nodes[child2].height - m_nodes[child1].height);
 | |
| 		maxBalance = b2Max(maxBalance, balance);
 | |
| 	}
 | |
| 
 | |
| 	return maxBalance;
 | |
| }
 | |
| 
 | |
| void b2DynamicTree::RebuildBottomUp()
 | |
| {
 | |
| 	int32* nodes = (int32*)b2Alloc(m_nodeCount * sizeof(int32));
 | |
| 	int32 count = 0;
 | |
| 
 | |
| 	// Build array of leaves. Free the rest.
 | |
| 	for (int32 i = 0; i < m_nodeCapacity; ++i)
 | |
| 	{
 | |
| 		if (m_nodes[i].height < 0)
 | |
| 		{
 | |
| 			// free node in pool
 | |
| 			continue;
 | |
| 		}
 | |
| 
 | |
| 		if (m_nodes[i].IsLeaf())
 | |
| 		{
 | |
| 			m_nodes[i].parent = b2_nullNode;
 | |
| 			nodes[count] = i;
 | |
| 			++count;
 | |
| 		}
 | |
| 		else
 | |
| 		{
 | |
| 			FreeNode(i);
 | |
| 		}
 | |
| 	}
 | |
| 
 | |
| 	while (count > 1)
 | |
| 	{
 | |
| 		float32 minCost = b2_maxFloat;
 | |
| 		int32 iMin = -1, jMin = -1;
 | |
| 		for (int32 i = 0; i < count; ++i)
 | |
| 		{
 | |
| 			b2AABB aabbi = m_nodes[nodes[i]].aabb;
 | |
| 
 | |
| 			for (int32 j = i + 1; j < count; ++j)
 | |
| 			{
 | |
| 				b2AABB aabbj = m_nodes[nodes[j]].aabb;
 | |
| 				b2AABB b;
 | |
| 				b.Combine(aabbi, aabbj);
 | |
| 				float32 cost = b.GetPerimeter();
 | |
| 				if (cost < minCost)
 | |
| 				{
 | |
| 					iMin = i;
 | |
| 					jMin = j;
 | |
| 					minCost = cost;
 | |
| 				}
 | |
| 			}
 | |
| 		}
 | |
| 
 | |
| 		int32 index1 = nodes[iMin];
 | |
| 		int32 index2 = nodes[jMin];
 | |
| 		b2TreeNode* child1 = m_nodes + index1;
 | |
| 		b2TreeNode* child2 = m_nodes + index2;
 | |
| 
 | |
| 		int32 parentIndex = AllocateNode();
 | |
| 		b2TreeNode* parent = m_nodes + parentIndex;
 | |
| 		parent->child1 = index1;
 | |
| 		parent->child2 = index2;
 | |
| 		parent->height = 1 + b2Max(child1->height, child2->height);
 | |
| 		parent->aabb.Combine(child1->aabb, child2->aabb);
 | |
| 		parent->parent = b2_nullNode;
 | |
| 
 | |
| 		child1->parent = parentIndex;
 | |
| 		child2->parent = parentIndex;
 | |
| 
 | |
| 		nodes[jMin] = nodes[count-1];
 | |
| 		nodes[iMin] = parentIndex;
 | |
| 		--count;
 | |
| 	}
 | |
| 
 | |
| 	m_root = nodes[0];
 | |
| 	b2Free(nodes);
 | |
| 
 | |
| 	Validate();
 | |
| }
 | |
| 
 | |
| void b2DynamicTree::ShiftOrigin(const b2Vec2& newOrigin)
 | |
| {
 | |
| 	// Build array of leaves. Free the rest.
 | |
| 	for (int32 i = 0; i < m_nodeCapacity; ++i)
 | |
| 	{
 | |
| 		m_nodes[i].aabb.lowerBound -= newOrigin;
 | |
| 		m_nodes[i].aabb.upperBound -= newOrigin;
 | |
| 	}
 | |
| }
 |