1034 lines
34 KiB
C#
1034 lines
34 KiB
C#
/*
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* Farseer Physics Engine:
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* Copyright (c) 2012 Ian Qvist
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*
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* Original source Box2D:
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* Copyright (c) 2006-2011 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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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using FarseerPhysics.Common;
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using Microsoft.Xna.Framework;
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namespace FarseerPhysics.Collision
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{
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/// <summary>
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/// A node in the dynamic tree. The client does not interact with this directly.
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/// </summary>
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internal class TreeNode<T>
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{
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/// <summary>
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/// Enlarged AABB
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/// </summary>
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internal AABB AABB;
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internal int Child1;
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internal int Child2;
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internal int Height;
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internal int ParentOrNext;
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internal T UserData;
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internal bool IsLeaf()
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{
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return Child1 == DynamicTree<T>.NullNode;
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}
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}
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/// <summary>
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/// A dynamic tree arranges data in a binary tree to accelerate
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/// queries such as volume queries and ray casts. Leafs are proxies
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/// with an AABB. In the tree we expand the proxy AABB by Settings.b2_fatAABBFactor
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/// so that the proxy AABB is bigger than the client object. This allows the client
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/// object to move by small amounts without triggering a tree update.
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///
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/// Nodes are pooled and relocatable, so we use node indices rather than pointers.
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/// </summary>
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public class DynamicTree<T>
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{
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private Stack<int> _raycastStack = new Stack<int>(256);
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private Stack<int> _queryStack = new Stack<int>(256);
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private int _freeList;
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private int _nodeCapacity;
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private int _nodeCount;
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private TreeNode<T>[] _nodes;
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private int _root;
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internal const int NullNode = -1;
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/// <summary>
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/// Constructing the tree initializes the node pool.
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/// </summary>
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public DynamicTree()
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{
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_root = NullNode;
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_nodeCapacity = 16;
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_nodeCount = 0;
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_nodes = new TreeNode<T>[_nodeCapacity];
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// Build a linked list for the free list.
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for (int i = 0; i < _nodeCapacity - 1; ++i)
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{
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_nodes[i] = new TreeNode<T>();
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_nodes[i].ParentOrNext = i + 1;
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_nodes[i].Height = 1;
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}
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_nodes[_nodeCapacity - 1] = new TreeNode<T>();
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_nodes[_nodeCapacity - 1].ParentOrNext = NullNode;
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_nodes[_nodeCapacity - 1].Height = 1;
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_freeList = 0;
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}
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/// <summary>
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/// Compute the height of the binary tree in O(N) time. Should not be called often.
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/// </summary>
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public int Height
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{
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get
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{
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if (_root == NullNode)
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{
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return 0;
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}
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return _nodes[_root].Height;
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}
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}
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/// <summary>
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/// Get the ratio of the sum of the node areas to the root area.
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/// </summary>
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public float AreaRatio
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{
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get
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{
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if (_root == NullNode)
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{
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return 0.0f;
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}
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TreeNode<T> root = _nodes[_root];
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float rootArea = root.AABB.Perimeter;
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float totalArea = 0.0f;
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for (int i = 0; i < _nodeCapacity; ++i)
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{
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TreeNode<T> node = _nodes[i];
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if (node.Height < 0)
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{
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// Free node in pool
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continue;
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}
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totalArea += node.AABB.Perimeter;
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}
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return totalArea / rootArea;
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}
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}
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/// <summary>
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/// Get the maximum balance of an node in the tree. The balance is the difference
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/// in height of the two children of a node.
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/// </summary>
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public int MaxBalance
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{
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get
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{
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int maxBalance = 0;
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for (int i = 0; i < _nodeCapacity; ++i)
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{
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TreeNode<T> node = _nodes[i];
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if (node.Height <= 1)
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{
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continue;
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}
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Debug.Assert(node.IsLeaf() == false);
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int child1 = node.Child1;
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int child2 = node.Child2;
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int balance = Math.Abs(_nodes[child2].Height - _nodes[child1].Height);
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maxBalance = Math.Max(maxBalance, balance);
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}
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return maxBalance;
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}
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}
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/// <summary>
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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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/// /// </summary>
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/// <param name="aabb">The aabb.</param>
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/// <param name="userData">The user data.</param>
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/// <returns>Index of the created proxy</returns>
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public int AddProxy(ref AABB aabb, T userData)
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{
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int proxyId = AllocateNode();
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// Fatten the aabb.
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Vector2 r = new Vector2(Settings.AABBExtension, Settings.AABBExtension);
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_nodes[proxyId].AABB.LowerBound = aabb.LowerBound - r;
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_nodes[proxyId].AABB.UpperBound = aabb.UpperBound + r;
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_nodes[proxyId].UserData = userData;
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_nodes[proxyId].Height = 0;
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InsertLeaf(proxyId);
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return proxyId;
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}
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/// <summary>
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/// Destroy a proxy. This asserts if the id is invalid.
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/// </summary>
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/// <param name="proxyId">The proxy id.</param>
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public void RemoveProxy(int proxyId)
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{
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Debug.Assert(0 <= proxyId && proxyId < _nodeCapacity);
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Debug.Assert(_nodes[proxyId].IsLeaf());
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RemoveLeaf(proxyId);
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FreeNode(proxyId);
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}
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/// <summary>
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/// Move a proxy with a swepted AABB. If the proxy has moved outside of its fattened AABB,
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/// then the proxy is removed from the tree and re-inserted. Otherwise
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/// the function returns immediately.
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/// </summary>
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/// <param name="proxyId">The proxy id.</param>
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/// <param name="aabb">The aabb.</param>
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/// <param name="displacement">The displacement.</param>
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/// <returns>true if the proxy was re-inserted.</returns>
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public bool MoveProxy(int proxyId, ref AABB aabb, Vector2 displacement)
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{
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Debug.Assert(0 <= proxyId && proxyId < _nodeCapacity);
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Debug.Assert(_nodes[proxyId].IsLeaf());
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if (_nodes[proxyId].AABB.Contains(ref aabb))
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{
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return false;
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}
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RemoveLeaf(proxyId);
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// Extend AABB.
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AABB b = aabb;
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Vector2 r = new Vector2(Settings.AABBExtension, Settings.AABBExtension);
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b.LowerBound = b.LowerBound - r;
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b.UpperBound = b.UpperBound + r;
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// Predict AABB displacement.
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Vector2 d = Settings.AABBMultiplier * displacement;
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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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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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_nodes[proxyId].AABB = b;
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InsertLeaf(proxyId);
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return true;
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}
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/// <summary>
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/// Get proxy user data.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="proxyId">The proxy id.</param>
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/// <returns>the proxy user data or 0 if the id is invalid.</returns>
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public T GetUserData(int proxyId)
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{
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Debug.Assert(0 <= proxyId && proxyId < _nodeCapacity);
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return _nodes[proxyId].UserData;
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}
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/// <summary>
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/// Get the fat AABB for a proxy.
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/// </summary>
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/// <param name="proxyId">The proxy id.</param>
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/// <param name="fatAABB">The fat AABB.</param>
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public void GetFatAABB(int proxyId, out AABB fatAABB)
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{
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Debug.Assert(0 <= proxyId && proxyId < _nodeCapacity);
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fatAABB = _nodes[proxyId].AABB;
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}
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/// <summary>
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/// Query an AABB for overlapping proxies. The callback class
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/// is called for each proxy that overlaps the supplied AABB.
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/// </summary>
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/// <param name="callback">The callback.</param>
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/// <param name="aabb">The aabb.</param>
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public void Query(Func<int, bool> callback, ref AABB aabb)
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{
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_queryStack.Clear();
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_queryStack.Push(_root);
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while (_queryStack.Count > 0)
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{
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int nodeId = _queryStack.Pop();
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if (nodeId == NullNode)
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{
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continue;
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}
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TreeNode<T> node = _nodes[nodeId];
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if (AABB.TestOverlap(ref node.AABB, ref aabb))
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{
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if (node.IsLeaf())
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{
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bool proceed = callback(nodeId);
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if (proceed == false)
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{
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return;
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}
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}
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else
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{
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_queryStack.Push(node.Child1);
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_queryStack.Push(node.Child2);
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}
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}
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}
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}
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/// <summary>
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/// Ray-cast against the proxies in the tree. This relies on the callback
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/// to perform a exact ray-cast in the case were the proxy contains a Shape.
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/// The callback also performs the any collision filtering. This has performance
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/// roughly equal to k * log(n), where k is the number of collisions and n is the
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/// number of proxies in the tree.
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/// </summary>
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/// <param name="callback">A callback class that is called for each proxy that is hit by the ray.</param>
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/// <param name="input">The ray-cast input data. The ray extends from p1 to p1 + maxFraction * (p2 - p1).</param>
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public void RayCast(Func<RayCastInput, int, float> callback, ref RayCastInput input)
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{
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Vector2 p1 = input.Point1;
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Vector2 p2 = input.Point2;
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Vector2 r = p2 - p1;
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Debug.Assert(r.LengthSquared() > 0.0f);
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r.Normalize();
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// v is perpendicular to the segment.
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Vector2 absV = MathUtils.Abs(new Vector2(-r.Y, r.X)); //FPE: Inlined the 'v' variable
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// Separating axis for segment (Gino, p80).
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// |dot(v, p1 - c)| > dot(|v|, h)
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float maxFraction = input.MaxFraction;
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// Build a bounding box for the segment.
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AABB segmentAABB = new AABB();
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{
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Vector2 t = p1 + maxFraction * (p2 - p1);
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Vector2.Min(ref p1, ref t, out segmentAABB.LowerBound);
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Vector2.Max(ref p1, ref t, out segmentAABB.UpperBound);
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}
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_raycastStack.Clear();
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_raycastStack.Push(_root);
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while (_raycastStack.Count > 0)
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{
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int nodeId = _raycastStack.Pop();
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if (nodeId == NullNode)
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{
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continue;
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}
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TreeNode<T> node = _nodes[nodeId];
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if (AABB.TestOverlap(ref node.AABB, ref segmentAABB) == false)
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{
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continue;
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}
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// Separating axis for segment (Gino, p80).
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// |dot(v, p1 - c)| > dot(|v|, h)
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Vector2 c = node.AABB.Center;
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Vector2 h = node.AABB.Extents;
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float separation = Math.Abs(Vector2.Dot(new Vector2(-r.Y, r.X), p1 - c)) - Vector2.Dot(absV, h);
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if (separation > 0.0f)
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{
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continue;
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}
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if (node.IsLeaf())
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{
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RayCastInput subInput;
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subInput.Point1 = input.Point1;
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subInput.Point2 = input.Point2;
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subInput.MaxFraction = maxFraction;
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float value = callback(subInput, nodeId);
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if (value == 0.0f)
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{
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// the client has terminated the raycast.
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return;
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}
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if (value > 0.0f)
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{
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// Update segment bounding box.
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maxFraction = value;
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Vector2 t = p1 + maxFraction * (p2 - p1);
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segmentAABB.LowerBound = Vector2.Min(p1, t);
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segmentAABB.UpperBound = Vector2.Max(p1, t);
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}
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}
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else
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{
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_raycastStack.Push(node.Child1);
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_raycastStack.Push(node.Child2);
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}
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}
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}
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private int AllocateNode()
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{
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// Expand the node pool as needed.
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if (_freeList == NullNode)
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{
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Debug.Assert(_nodeCount == _nodeCapacity);
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// The free list is empty. Rebuild a bigger pool.
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TreeNode<T>[] oldNodes = _nodes;
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_nodeCapacity *= 2;
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_nodes = new TreeNode<T>[_nodeCapacity];
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Array.Copy(oldNodes, _nodes, _nodeCount);
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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 (int i = _nodeCount; i < _nodeCapacity - 1; ++i)
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{
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_nodes[i] = new TreeNode<T>();
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_nodes[i].ParentOrNext = i + 1;
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_nodes[i].Height = -1;
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}
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_nodes[_nodeCapacity - 1] = new TreeNode<T>();
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_nodes[_nodeCapacity - 1].ParentOrNext = NullNode;
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_nodes[_nodeCapacity - 1].Height = -1;
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_freeList = _nodeCount;
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}
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// Peel a node off the free list.
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int nodeId = _freeList;
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_freeList = _nodes[nodeId].ParentOrNext;
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_nodes[nodeId].ParentOrNext = NullNode;
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_nodes[nodeId].Child1 = NullNode;
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_nodes[nodeId].Child2 = NullNode;
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_nodes[nodeId].Height = 0;
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_nodes[nodeId].UserData = default(T);
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++_nodeCount;
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return nodeId;
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}
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private void FreeNode(int nodeId)
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{
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Debug.Assert(0 <= nodeId && nodeId < _nodeCapacity);
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Debug.Assert(0 < _nodeCount);
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_nodes[nodeId].ParentOrNext = _freeList;
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_nodes[nodeId].Height = -1;
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_freeList = nodeId;
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--_nodeCount;
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}
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private void InsertLeaf(int leaf)
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{
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if (_root == NullNode)
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{
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_root = leaf;
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_nodes[_root].ParentOrNext = NullNode;
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return;
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}
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// Find the best sibling for this node
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AABB leafAABB = _nodes[leaf].AABB;
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int index = _root;
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while (_nodes[index].IsLeaf() == false)
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{
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int child1 = _nodes[index].Child1;
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int child2 = _nodes[index].Child2;
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float area = _nodes[index].AABB.Perimeter;
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AABB combinedAABB = new AABB();
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combinedAABB.Combine(ref _nodes[index].AABB, ref leafAABB);
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float combinedArea = combinedAABB.Perimeter;
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// Cost of creating a new parent for this node and the new leaf
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float cost = 2.0f * combinedArea;
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// Minimum cost of pushing the leaf further down the tree
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float inheritanceCost = 2.0f * (combinedArea - area);
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// Cost of descending into child1
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float cost1;
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if (_nodes[child1].IsLeaf())
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{
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AABB aabb = new AABB();
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aabb.Combine(ref leafAABB, ref _nodes[child1].AABB);
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cost1 = aabb.Perimeter + inheritanceCost;
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}
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else
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{
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AABB aabb = new AABB();
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aabb.Combine(ref leafAABB, ref _nodes[child1].AABB);
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float oldArea = _nodes[child1].AABB.Perimeter;
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float newArea = aabb.Perimeter;
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cost1 = (newArea - oldArea) + inheritanceCost;
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}
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// Cost of descending into child2
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float cost2;
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if (_nodes[child2].IsLeaf())
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{
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AABB aabb = new AABB();
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aabb.Combine(ref leafAABB, ref _nodes[child2].AABB);
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cost2 = aabb.Perimeter + inheritanceCost;
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}
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else
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{
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AABB aabb = new AABB();
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aabb.Combine(ref leafAABB, ref _nodes[child2].AABB);
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float oldArea = _nodes[child2].AABB.Perimeter;
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float newArea = aabb.Perimeter;
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cost2 = newArea - oldArea + inheritanceCost;
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}
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// Descend according to the minimum cost.
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if (cost < cost1 && cost1 < cost2)
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{
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break;
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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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|
|
|
int sibling = index;
|
|
|
|
// Create a new parent.
|
|
int oldParent = _nodes[sibling].ParentOrNext;
|
|
int newParent = AllocateNode();
|
|
_nodes[newParent].ParentOrNext = oldParent;
|
|
_nodes[newParent].UserData = default(T);
|
|
_nodes[newParent].AABB.Combine(ref leafAABB, ref _nodes[sibling].AABB);
|
|
_nodes[newParent].Height = _nodes[sibling].Height + 1;
|
|
|
|
if (oldParent != NullNode)
|
|
{
|
|
// The sibling was not the root.
|
|
if (_nodes[oldParent].Child1 == sibling)
|
|
{
|
|
_nodes[oldParent].Child1 = newParent;
|
|
}
|
|
else
|
|
{
|
|
_nodes[oldParent].Child2 = newParent;
|
|
}
|
|
|
|
_nodes[newParent].Child1 = sibling;
|
|
_nodes[newParent].Child2 = leaf;
|
|
_nodes[sibling].ParentOrNext = newParent;
|
|
_nodes[leaf].ParentOrNext = newParent;
|
|
}
|
|
else
|
|
{
|
|
// The sibling was the root.
|
|
_nodes[newParent].Child1 = sibling;
|
|
_nodes[newParent].Child2 = leaf;
|
|
_nodes[sibling].ParentOrNext = newParent;
|
|
_nodes[leaf].ParentOrNext = newParent;
|
|
_root = newParent;
|
|
}
|
|
|
|
// Walk back up the tree fixing heights and AABBs
|
|
index = _nodes[leaf].ParentOrNext;
|
|
while (index != NullNode)
|
|
{
|
|
index = Balance(index);
|
|
|
|
int child1 = _nodes[index].Child1;
|
|
int child2 = _nodes[index].Child2;
|
|
|
|
Debug.Assert(child1 != NullNode);
|
|
Debug.Assert(child2 != NullNode);
|
|
|
|
_nodes[index].Height = 1 + Math.Max(_nodes[child1].Height, _nodes[child2].Height);
|
|
_nodes[index].AABB.Combine(ref _nodes[child1].AABB, ref _nodes[child2].AABB);
|
|
|
|
index = _nodes[index].ParentOrNext;
|
|
}
|
|
|
|
//Validate();
|
|
}
|
|
|
|
private void RemoveLeaf(int leaf)
|
|
{
|
|
if (leaf == _root)
|
|
{
|
|
_root = NullNode;
|
|
return;
|
|
}
|
|
|
|
int parent = _nodes[leaf].ParentOrNext;
|
|
int grandParent = _nodes[parent].ParentOrNext;
|
|
int sibling;
|
|
if (_nodes[parent].Child1 == leaf)
|
|
{
|
|
sibling = _nodes[parent].Child2;
|
|
}
|
|
else
|
|
{
|
|
sibling = _nodes[parent].Child1;
|
|
}
|
|
|
|
if (grandParent != NullNode)
|
|
{
|
|
// Destroy parent and connect sibling to grandParent.
|
|
if (_nodes[grandParent].Child1 == parent)
|
|
{
|
|
_nodes[grandParent].Child1 = sibling;
|
|
}
|
|
else
|
|
{
|
|
_nodes[grandParent].Child2 = sibling;
|
|
}
|
|
_nodes[sibling].ParentOrNext = grandParent;
|
|
FreeNode(parent);
|
|
|
|
// Adjust ancestor bounds.
|
|
int index = grandParent;
|
|
while (index != NullNode)
|
|
{
|
|
index = Balance(index);
|
|
|
|
int child1 = _nodes[index].Child1;
|
|
int child2 = _nodes[index].Child2;
|
|
|
|
_nodes[index].AABB.Combine(ref _nodes[child1].AABB, ref _nodes[child2].AABB);
|
|
_nodes[index].Height = 1 + Math.Max(_nodes[child1].Height, _nodes[child2].Height);
|
|
|
|
index = _nodes[index].ParentOrNext;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
_root = sibling;
|
|
_nodes[sibling].ParentOrNext = NullNode;
|
|
FreeNode(parent);
|
|
}
|
|
|
|
//Validate();
|
|
}
|
|
|
|
/// <summary>
|
|
/// Perform a left or right rotation if node A is imbalanced.
|
|
/// </summary>
|
|
/// <param name="iA"></param>
|
|
/// <returns>the new root index.</returns>
|
|
private int Balance(int iA)
|
|
{
|
|
Debug.Assert(iA != NullNode);
|
|
|
|
TreeNode<T> A = _nodes[iA];
|
|
if (A.IsLeaf() || A.Height < 2)
|
|
{
|
|
return iA;
|
|
}
|
|
|
|
int iB = A.Child1;
|
|
int iC = A.Child2;
|
|
Debug.Assert(0 <= iB && iB < _nodeCapacity);
|
|
Debug.Assert(0 <= iC && iC < _nodeCapacity);
|
|
|
|
TreeNode<T> B = _nodes[iB];
|
|
TreeNode<T> C = _nodes[iC];
|
|
|
|
int balance = C.Height - B.Height;
|
|
|
|
// Rotate C up
|
|
if (balance > 1)
|
|
{
|
|
int iF = C.Child1;
|
|
int iG = C.Child2;
|
|
TreeNode<T> F = _nodes[iF];
|
|
TreeNode<T> G = _nodes[iG];
|
|
Debug.Assert(0 <= iF && iF < _nodeCapacity);
|
|
Debug.Assert(0 <= iG && iG < _nodeCapacity);
|
|
|
|
// Swap A and C
|
|
C.Child1 = iA;
|
|
C.ParentOrNext = A.ParentOrNext;
|
|
A.ParentOrNext = iC;
|
|
|
|
// A's old parent should point to C
|
|
if (C.ParentOrNext != NullNode)
|
|
{
|
|
if (_nodes[C.ParentOrNext].Child1 == iA)
|
|
{
|
|
_nodes[C.ParentOrNext].Child1 = iC;
|
|
}
|
|
else
|
|
{
|
|
Debug.Assert(_nodes[C.ParentOrNext].Child2 == iA);
|
|
_nodes[C.ParentOrNext].Child2 = iC;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
_root = iC;
|
|
}
|
|
|
|
// Rotate
|
|
if (F.Height > G.Height)
|
|
{
|
|
C.Child2 = iF;
|
|
A.Child2 = iG;
|
|
G.ParentOrNext = iA;
|
|
A.AABB.Combine(ref B.AABB, ref G.AABB);
|
|
C.AABB.Combine(ref A.AABB, ref F.AABB);
|
|
|
|
A.Height = 1 + Math.Max(B.Height, G.Height);
|
|
C.Height = 1 + Math.Max(A.Height, F.Height);
|
|
}
|
|
else
|
|
{
|
|
C.Child2 = iG;
|
|
A.Child2 = iF;
|
|
F.ParentOrNext = iA;
|
|
A.AABB.Combine(ref B.AABB, ref F.AABB);
|
|
C.AABB.Combine(ref A.AABB, ref G.AABB);
|
|
|
|
A.Height = 1 + Math.Max(B.Height, F.Height);
|
|
C.Height = 1 + Math.Max(A.Height, G.Height);
|
|
}
|
|
|
|
return iC;
|
|
}
|
|
|
|
// Rotate B up
|
|
if (balance < -1)
|
|
{
|
|
int iD = B.Child1;
|
|
int iE = B.Child2;
|
|
TreeNode<T> D = _nodes[iD];
|
|
TreeNode<T> E = _nodes[iE];
|
|
Debug.Assert(0 <= iD && iD < _nodeCapacity);
|
|
Debug.Assert(0 <= iE && iE < _nodeCapacity);
|
|
|
|
// Swap A and B
|
|
B.Child1 = iA;
|
|
B.ParentOrNext = A.ParentOrNext;
|
|
A.ParentOrNext = iB;
|
|
|
|
// A's old parent should point to B
|
|
if (B.ParentOrNext != NullNode)
|
|
{
|
|
if (_nodes[B.ParentOrNext].Child1 == iA)
|
|
{
|
|
_nodes[B.ParentOrNext].Child1 = iB;
|
|
}
|
|
else
|
|
{
|
|
Debug.Assert(_nodes[B.ParentOrNext].Child2 == iA);
|
|
_nodes[B.ParentOrNext].Child2 = iB;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
_root = iB;
|
|
}
|
|
|
|
// Rotate
|
|
if (D.Height > E.Height)
|
|
{
|
|
B.Child2 = iD;
|
|
A.Child1 = iE;
|
|
E.ParentOrNext = iA;
|
|
A.AABB.Combine(ref C.AABB, ref E.AABB);
|
|
B.AABB.Combine(ref A.AABB, ref D.AABB);
|
|
|
|
A.Height = 1 + Math.Max(C.Height, E.Height);
|
|
B.Height = 1 + Math.Max(A.Height, D.Height);
|
|
}
|
|
else
|
|
{
|
|
B.Child2 = iE;
|
|
A.Child1 = iD;
|
|
D.ParentOrNext = iA;
|
|
A.AABB.Combine(ref C.AABB, ref D.AABB);
|
|
B.AABB.Combine(ref A.AABB, ref E.AABB);
|
|
|
|
A.Height = 1 + Math.Max(C.Height, D.Height);
|
|
B.Height = 1 + Math.Max(A.Height, E.Height);
|
|
}
|
|
|
|
return iB;
|
|
}
|
|
|
|
return iA;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Compute the height of a sub-tree.
|
|
/// </summary>
|
|
/// <param name="nodeId">The node id to use as parent.</param>
|
|
/// <returns>The height of the tree.</returns>
|
|
public int ComputeHeight(int nodeId)
|
|
{
|
|
Debug.Assert(0 <= nodeId && nodeId < _nodeCapacity);
|
|
TreeNode<T> node = _nodes[nodeId];
|
|
|
|
if (node.IsLeaf())
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int height1 = ComputeHeight(node.Child1);
|
|
int height2 = ComputeHeight(node.Child2);
|
|
return 1 + Math.Max(height1, height2);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Compute the height of the entire tree.
|
|
/// </summary>
|
|
/// <returns>The height of the tree.</returns>
|
|
public int ComputeHeight()
|
|
{
|
|
int height = ComputeHeight(_root);
|
|
return height;
|
|
}
|
|
|
|
public void ValidateStructure(int index)
|
|
{
|
|
if (index == NullNode)
|
|
{
|
|
return;
|
|
}
|
|
|
|
if (index == _root)
|
|
{
|
|
Debug.Assert(_nodes[index].ParentOrNext == NullNode);
|
|
}
|
|
|
|
TreeNode<T> node = _nodes[index];
|
|
|
|
int child1 = node.Child1;
|
|
int child2 = node.Child2;
|
|
|
|
if (node.IsLeaf())
|
|
{
|
|
Debug.Assert(child1 == NullNode);
|
|
Debug.Assert(child2 == NullNode);
|
|
Debug.Assert(node.Height == 0);
|
|
return;
|
|
}
|
|
|
|
Debug.Assert(0 <= child1 && child1 < _nodeCapacity);
|
|
Debug.Assert(0 <= child2 && child2 < _nodeCapacity);
|
|
|
|
Debug.Assert(_nodes[child1].ParentOrNext == index);
|
|
Debug.Assert(_nodes[child2].ParentOrNext == index);
|
|
|
|
ValidateStructure(child1);
|
|
ValidateStructure(child2);
|
|
}
|
|
|
|
public void ValidateMetrics(int index)
|
|
{
|
|
if (index == NullNode)
|
|
{
|
|
return;
|
|
}
|
|
|
|
TreeNode<T> node = _nodes[index];
|
|
|
|
int child1 = node.Child1;
|
|
int child2 = node.Child2;
|
|
|
|
if (node.IsLeaf())
|
|
{
|
|
Debug.Assert(child1 == NullNode);
|
|
Debug.Assert(child2 == NullNode);
|
|
Debug.Assert(node.Height == 0);
|
|
return;
|
|
}
|
|
|
|
Debug.Assert(0 <= child1 && child1 < _nodeCapacity);
|
|
Debug.Assert(0 <= child2 && child2 < _nodeCapacity);
|
|
|
|
int height1 = _nodes[child1].Height;
|
|
int height2 = _nodes[child2].Height;
|
|
int height = 1 + Math.Max(height1, height2);
|
|
Debug.Assert(node.Height == height);
|
|
|
|
AABB AABB = new AABB();
|
|
AABB.Combine(ref _nodes[child1].AABB, ref _nodes[child2].AABB);
|
|
|
|
Debug.Assert(AABB.LowerBound == node.AABB.LowerBound);
|
|
Debug.Assert(AABB.UpperBound == node.AABB.UpperBound);
|
|
|
|
ValidateMetrics(child1);
|
|
ValidateMetrics(child2);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Validate this tree. For testing.
|
|
/// </summary>
|
|
public void Validate()
|
|
{
|
|
ValidateStructure(_root);
|
|
ValidateMetrics(_root);
|
|
|
|
int freeCount = 0;
|
|
int freeIndex = _freeList;
|
|
while (freeIndex != NullNode)
|
|
{
|
|
Debug.Assert(0 <= freeIndex && freeIndex < _nodeCapacity);
|
|
freeIndex = _nodes[freeIndex].ParentOrNext;
|
|
++freeCount;
|
|
}
|
|
|
|
Debug.Assert(Height == ComputeHeight());
|
|
|
|
Debug.Assert(_nodeCount + freeCount == _nodeCapacity);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Build an optimal tree. Very expensive. For testing.
|
|
/// </summary>
|
|
public void RebuildBottomUp()
|
|
{
|
|
int[] nodes = new int[_nodeCount];
|
|
int count = 0;
|
|
|
|
// Build array of leaves. Free the rest.
|
|
for (int i = 0; i < _nodeCapacity; ++i)
|
|
{
|
|
if (_nodes[i].Height < 0)
|
|
{
|
|
// free node in pool
|
|
continue;
|
|
}
|
|
|
|
if (_nodes[i].IsLeaf())
|
|
{
|
|
_nodes[i].ParentOrNext = NullNode;
|
|
nodes[count] = i;
|
|
++count;
|
|
}
|
|
else
|
|
{
|
|
FreeNode(i);
|
|
}
|
|
}
|
|
|
|
while (count > 1)
|
|
{
|
|
float minCost = Settings.MaxFloat;
|
|
int iMin = -1, jMin = -1;
|
|
for (int i = 0; i < count; ++i)
|
|
{
|
|
AABB AABBi = _nodes[nodes[i]].AABB;
|
|
|
|
for (int j = i + 1; j < count; ++j)
|
|
{
|
|
AABB AABBj = _nodes[nodes[j]].AABB;
|
|
AABB b = new AABB();
|
|
b.Combine(ref AABBi, ref AABBj);
|
|
float cost = b.Perimeter;
|
|
if (cost < minCost)
|
|
{
|
|
iMin = i;
|
|
jMin = j;
|
|
minCost = cost;
|
|
}
|
|
}
|
|
}
|
|
|
|
int index1 = nodes[iMin];
|
|
int index2 = nodes[jMin];
|
|
TreeNode<T> child1 = _nodes[index1];
|
|
TreeNode<T> child2 = _nodes[index2];
|
|
|
|
int parentIndex = AllocateNode();
|
|
TreeNode<T> parent = _nodes[parentIndex];
|
|
parent.Child1 = index1;
|
|
parent.Child2 = index2;
|
|
parent.Height = 1 + Math.Max(child1.Height, child2.Height);
|
|
parent.AABB.Combine(ref child1.AABB, ref child2.AABB);
|
|
parent.ParentOrNext = NullNode;
|
|
|
|
child1.ParentOrNext = parentIndex;
|
|
child2.ParentOrNext = parentIndex;
|
|
|
|
nodes[jMin] = nodes[count - 1];
|
|
nodes[iMin] = parentIndex;
|
|
--count;
|
|
}
|
|
|
|
_root = nodes[0];
|
|
|
|
Validate();
|
|
}
|
|
|
|
/// <summary>
|
|
/// Shift the origin of the nodes
|
|
/// </summary>
|
|
/// <param name="newOrigin">The displacement to use.</param>
|
|
public void ShiftOrigin(Vector2 newOrigin)
|
|
{
|
|
// Build array of leaves. Free the rest.
|
|
for (int i = 0; i < _nodeCapacity; ++i)
|
|
{
|
|
_nodes[i].AABB.LowerBound -= newOrigin;
|
|
_nodes[i].AABB.UpperBound -= newOrigin;
|
|
}
|
|
}
|
|
}
|
|
} |