Warning, file /education/gcompris/external/qml-box2d/Box2D/Collision/b2DynamicTree.cpp was not indexed or was modified since last indexation (in which case cross-reference links may be missing, inaccurate or erroneous).

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