/// <summary>
/// Removes the specified node from the tree.
/// </summary>
public void RemoveNode(SphereTreeNode <T> node)
{
// If the node is not the root node and if it has a parent...
if (!node.IsRoot && node.Parent != null)
{
// Remove the node from its parent
SphereTreeNode <T> parentNode = node.Parent;
parentNode.RemoveChild(node);
// Move up the hierarhcy and remove all parents which don't have any children any more.
// Note: We will always stop at the root node. The root node is allowed to exist even
// if it has no children.
while (parentNode.Parent != null && parentNode.HasNoChildren && !parentNode.IsRoot)
{
SphereTreeNode <T> newParent = parentNode.Parent;
newParent.RemoveChild(parentNode);
parentNode = newParent;
}
// At this point 'parentNode' references the deepest parent which has at least one child.
// Because we have removed children from it, its volume must be recalculated, so we add
// it to the recomputation queue.
// Note: Even if this function was called from 'PerformPendingUpdates' we still get correct
// results because the node will be added to the recomputation queue and it will be
// processed inside the recomputation 'while' loop from where this method is called.
AddNodeToRecomputationQueue(parentNode);
}
}
/// <summary>
/// This is a recursive method which is responsible for integration the specified
/// node inside the tree.
/// </summary>
private void IntegrateTerminalNodeRecurse(SphereTreeNode <T> nodeToIntegrate, SphereTreeNode <T> parentNode)
{
// If this node still has room for children, we will add the integration node here. This 'if' statement
// will also handle the special case in which only the root node currently exists inside the tree.
if (parentNode.NumberOfChildren < _numberOfChildNodesPerNode)
{
// Add the node as a child of the parent node and ensure that the root node encapsulates it
parentNode.AddChild(nodeToIntegrate);
parentNode.EncapsulateChildNode(nodeToIntegrate);
}
else
{
// If there is no more room, we will proceed by choosing one of the parent's children which
// is closest to the node that we want to integrate. We choose the closest node because when
// the node will be added as a child of it, we want the parent to grow as little as possible.
List <SphereTreeNode <T> > children = parentNode.Children;
SphereTreeNode <T> closestChild = FindClosestNode(children, nodeToIntegrate);
if (closestChild == null)
{
return;
}
// If the closest child is not a terminal node, recurse.
if (!closestChild.IsTerminal)
{
IntegrateTerminalNodeRecurse(nodeToIntegrate, closestChild);
}
else
{
// If we reached a terminal node, we create a new node which encapsulates 'closestChild' and 'nodeToIntegrate'
// and then we replace 'closestChild' with this new node. The first step is to create the sphere of this
// new node. It doesn't matter how big this sphere is initially because we will call 'EncapsulateChildNode'
// later.
Sphere newNodeSphere = closestChild.Sphere;
// Create the node using the sphere we just calculated
SphereTreeNode <T> newNode = new SphereTreeNode <T>(newNodeSphere, this, default(T));
newNode.SetFlag(SphereTreeNodeFlags.SuperSphere);
// Replace 'closestChild' with the new node and add both 'closestChild' and 'nodeToIntegrate' as children of it
parentNode.RemoveChild(closestChild);
parentNode.AddChild(newNode);
newNode.AddChild(nodeToIntegrate);
newNode.AddChild(closestChild);
// Encapsulate the children inside the new node
newNode.EncapsulateChildNode(closestChild);
newNode.EncapsulateChildNode(nodeToIntegrate);
// Ensure that the new node is fully contained inside the parent node
parentNode.EncapsulateChildNode(newNode);
}
}
}
/// <summary>
/// This method is called when the sphere of a terminal node has been updated.
/// </summary>
private void OnTerminalNodeSphereUpdated(SphereTreeNode <T> terminalNode)
{
// If the node is already marked for reintegration, there is nothing left for us to do
if (terminalNode.MustIntegrate)
{
return;
}
// If the node is now outside of its parent, it may now be closer to another parent and associating
// it with that new parent may provide better space/volume savings. So we remove the node from its
// parent and add it to the integration queue so that it can be reintegrated. During the integration
// process, the algorithm may find a more optimal parent or the same one if a more optimal one doesn't
// exist.
// Note: We are only removing the child from its parent if it went outside of its parent volume. It may
// probably be a better idea to always check the surrounding parents and see if a more optimal one
// exists even if the node doesn't pierce its parent's skin. For the moment however, we will only
// remove the child from its parent if it pierced its skin.
SphereTreeNode <T> parentNode = terminalNode.Parent;
float distanceToParentNodeExitPoint = parentNode.GetDistanceToNodeExitPoint(terminalNode);
if (distanceToParentNodeExitPoint > parentNode.Radius)
{
// Note: It may be a good idea to check if the node contains only one child after removal. In that
// case the node itself can be removed and its child moved up the hierarchy. However, for the
// moment we'll keep things simple.
// Remove the child from its parent and add it to the integration queue. Adding it to
// the integration queue is necessary in order to ensure that it gets reassigned to
// the correct parrent based on its current position.
parentNode.RemoveChild(terminalNode);
AddNodeToIntegrationQueue(terminalNode);
}
// Whenever a terminal node is updated, it's parent must gave its volume recomputed. We always do this
// regardless of whether or not the node was removed from the parent or not.
AddNodeToRecomputationQueue(parentNode);
}