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Fixed AABB tree building, which failed for certain large triangle meshes due to stack overflow.

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Now it has a safer check for unbalanced tree, and forces them to be balanced.
This commit is contained in:
ejcoumans
2007-01-04 22:31:31 +00:00
parent 99337454e3
commit ca973e9322
1 changed files with 37 additions and 3 deletions
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40
src/BulletCollision/CollisionShapes/btOptimizedBvh.cpp
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@@ -96,8 +96,19 @@ btOptimizedBvh::~btOptimizedBvh()
delete []m_contiguousNodes; delete []m_contiguousNodes;
} }
#ifdef DEBUG_TREE_BUILDING
int gStackDepth = 0;
int gMaxStackDepth = 0;
#endif //DEBUG_TREE_BUILDING
btOptimizedBvhNode* btOptimizedBvh::buildTree (NodeArray& leafNodes,int startIndex,int endIndex) btOptimizedBvhNode* btOptimizedBvh::buildTree (NodeArray& leafNodes,int startIndex,int endIndex)
{ {
#ifdef DEBUG_TREE_BUILDING
gStackDepth++;
if (gStackDepth > gMaxStackDepth)
gMaxStackDepth = gStackDepth;
#endif //DEBUG_TREE_BUILDING
btOptimizedBvhNode* internalNode; btOptimizedBvhNode* internalNode;
int splitAxis, splitIndex, i; int splitAxis, splitIndex, i;
@@ -108,6 +119,9 @@ btOptimizedBvhNode* btOptimizedBvh::buildTree (NodeArray& leafNodes,int startInd
if (numIndices==1) if (numIndices==1)
{ {
#ifdef DEBUG_TREE_BUILDING
gStackDepth--;
#endif //DEBUG_TREE_BUILDING
return new (&m_contiguousNodes[m_curNodeIndex++]) btOptimizedBvhNode(leafNodes[startIndex]); return new (&m_contiguousNodes[m_curNodeIndex++]) btOptimizedBvhNode(leafNodes[startIndex]);
} }
//calculate Best Splitting Axis and where to split it. Sort the incoming 'leafNodes' array within range 'startIndex/endIndex'. //calculate Best Splitting Axis and where to split it. Sort the incoming 'leafNodes' array within range 'startIndex/endIndex'.
@@ -132,7 +146,9 @@ btOptimizedBvhNode* btOptimizedBvh::buildTree (NodeArray& leafNodes,int startInd
//internalNode->m_escapeIndex; //internalNode->m_escapeIndex;
internalNode->m_leftChild = buildTree(leafNodes,startIndex,splitIndex); internalNode->m_leftChild = buildTree(leafNodes,startIndex,splitIndex);
internalNode->m_rightChild = buildTree(leafNodes,splitIndex,endIndex); internalNode->m_rightChild = buildTree(leafNodes,splitIndex,endIndex);
#ifdef DEBUG_TREE_BUILDING
gStackDepth--;
#endif //DEBUG_TREE_BUILDING
internalNode->m_escapeIndex = m_curNodeIndex - curIndex; internalNode->m_escapeIndex = m_curNodeIndex - curIndex;
return internalNode; return internalNode;
} }
@@ -167,10 +183,27 @@ int btOptimizedBvh::sortAndCalcSplittingIndex(NodeArray& leafNodes,int startInde
splitIndex++; splitIndex++;
} }
} }
if ((splitIndex==startIndex) || (splitIndex == (endIndex-1)))
//if the splitIndex causes unbalanced trees, fix this by using the center in between startIndex and endIndex
//otherwise the tree-building might fail due to stack-overflows in certain cases.
//unbalanced1 is unsafe: it can cause stack overflows
//bool unbalanced1 = ((splitIndex==startIndex) || (splitIndex == (endIndex-1)));
//unbalanced2 should work too: always use center (perfect balanced trees)
//bool unbalanced2 = true;
//this should be safe too:
int rangeBalancedIndices = numIndices/3;
bool unbalanced = ((splitIndex<=(startIndex+rangeBalancedIndices)) || (splitIndex >=(endIndex-1-rangeBalancedIndices)));
if (unbalanced)
{ {
splitIndex = startIndex+ (numIndices>>1); splitIndex = startIndex+ (numIndices>>1);
} }
bool unbal = (splitIndex==startIndex) || (splitIndex == (endIndex));
btAssert(!unbal);
return splitIndex; return splitIndex;
} }
@@ -185,7 +218,8 @@ int btOptimizedBvh::calcSplittingAxis(NodeArray& leafNodes,int startIndex,int en
for (i=startIndex;i<endIndex;i++) for (i=startIndex;i<endIndex;i++)
{ {
btVector3 center = btScalar(0.5)*(leafNodes[i].m_aabbMax+leafNodes[i].m_aabbMin); btOptimizedBvhNode& node = leafNodes[i];
btVector3 center = btScalar(0.5)*(node.m_aabbMax+node.m_aabbMin);
means+=center; means+=center;
} }
means *= (btScalar(1.)/(btScalar)numIndices); means *= (btScalar(1.)/(btScalar)numIndices);