public QuadTree(int maxDepth, int splitThreshold, AABB2D bounds)
{
m_MaxDepth = maxDepth;
m_NodeSplitThreshold = splitThreshold;
Root = new QuadNode();
Root.SetData(0, QuadNodeDirection.None, bounds);
}
//结点达到分裂的限定，进行结点的分裂
private void SplitNode(QuadNode node)
{
AABB2D bounds = node.Bounds;
Vector2 childNodeExtents = bounds.HalfExtents;
QuadNode childNode = m_NodePool.Get();
childNode.SetData(node.Depth + 1, QuadNodeDirection.LB, new AABB2D(bounds.Center - childNodeExtents, childNodeExtents));
node[QuadNodeDirection.LB] = childNode;
childNode = m_NodePool.Get();
childNode.SetData(node.Depth + 1, QuadNodeDirection.RB, new AABB2D(bounds.Center + new Vector2(childNodeExtents.x, -childNodeExtents.y), childNodeExtents));
node[QuadNodeDirection.RB] = childNode;
childNode = m_NodePool.Get();
childNode.SetData(node.Depth + 1, QuadNodeDirection.LT, new AABB2D(bounds.Center + new Vector2(-childNodeExtents.x, childNodeExtents.y), childNodeExtents));
node[QuadNodeDirection.LT] = childNode;
childNode = m_NodePool.Get();
childNode.SetData(node.Depth + 1, QuadNodeDirection.RT, new AABB2D(bounds.Center + childNodeExtents, childNodeExtents));
node[QuadNodeDirection.RT] = childNode;
}