void CornerBasedSplit(SpatialNode node, ISpatialObject obj, out SpatialNode splitNode)
{
foreach (var cornerChildren in m_CornerSplitChildren)
{
cornerChildren.Clear();
}
// separate children by their closest corners
m_CornerSplitChildren[FindClosestCornerIndex(node, obj)].Add(obj);
foreach (var child in node.children)
{
m_CornerSplitChildren[FindClosestCornerIndex(node, child)].Add(child);
}
// split children by closest corners along each axis
var splitLowX = new List <ISpatialObject>();
var splitHighX = new List <ISpatialObject>();
var splitLowY = new List <ISpatialObject>();
var splitHighY = new List <ISpatialObject>();
var splitLowZ = new List <ISpatialObject>();
var splitHighZ = new List <ISpatialObject>();
for (var i = 0; i < m_CornerSplitChildren.Length; ++i)
{
((i >> 2) % 2 > 0 ? splitHighX : splitLowX).AddRange(m_CornerSplitChildren[i]);
((i >> 1) % 2 > 0 ? splitHighY : splitLowY).AddRange(m_CornerSplitChildren[i]);
(i % 2 > 0 ? splitHighZ : splitLowZ).AddRange(m_CornerSplitChildren[i]);
}
// find the diff between the split node child counts
var dx = Mathf.Abs(splitLowX.Count - splitHighX.Count);
var dy = Mathf.Abs(splitLowY.Count - splitHighY.Count);
var dz = Mathf.Abs(splitLowZ.Count - splitHighZ.Count);
var bestSplits = new List <int>();
if (dx <= dy && dx <= dz)
{
bestSplits.Add(k_X);
}
if (dy <= dx && dy <= dz)
{
bestSplits.Add(k_Y);
}
if (dz <= dx && dz <= dy)
{
bestSplits.Add(k_Z);
}
// handle tiebreakers if multiple equal counts
var bestSplit = 0;
if (bestSplits.Count == 1)
{
bestSplit = bestSplits[0];
}
else
{
var overlaps = new List <float>();
var volumes = new List <float>();
foreach (var axis in bestSplits)
{
// tiebreaker uses overlaps and volume totals
switch (axis)
{
case k_X:
CalculateMinMax(splitLowX, out var minLowX, out var maxLowX);
CalculateMinMax(splitHighX, out var minHighX, out var maxHighX);
overlaps.Add(CalculateOverlap(minLowX, maxLowX, minHighX, maxHighX));
volumes.Add(CalculateVolume(minLowX, maxLowX) + CalculateVolume(minHighX, maxHighX));
break;
case k_Y:
CalculateMinMax(splitLowY, out var minLowY, out var maxLowY);
CalculateMinMax(splitHighY, out var minHighY, out var maxHighY);
overlaps.Add(CalculateOverlap(minLowY, maxLowY, minHighY, maxHighY));
volumes.Add(CalculateVolume(minLowY, maxLowY) + CalculateVolume(minHighY, maxHighY));
break;
case k_Z:
CalculateMinMax(splitLowZ, out var minLowZ, out var maxLowZ);
CalculateMinMax(splitHighZ, out var minHighZ, out var maxHighZ);
overlaps.Add(CalculateOverlap(minLowZ, maxLowZ, minHighZ, maxHighZ));
volumes.Add(CalculateVolume(minLowZ, maxLowZ) + CalculateVolume(minHighZ, maxHighZ));
break;
}
}
var bestOverlap = float.MaxValue;
var bestVolume = float.MaxValue;
for (var i = 0; i < bestSplits.Count; ++i)
{
// check overlap first, if equal check total volume
if (overlaps[i] > bestOverlap ||
Mathf.Approximately(overlaps[i], bestOverlap) && volumes[i] > bestVolume)
{
continue;
}
bestSplit = bestSplits[i];
bestOverlap = overlaps[i];
bestVolume = volumes[i];
}
}
SpatialNode smallNode = null;
SpatialNode bigNode = null;
node.children.Clear();
splitNode = new SpatialNode {
parent = node.parent
};
var nodeComparer = Comparer <ISpatialObject> .Default;
var splitNodeComparer = Comparer <ISpatialObject> .Default;
switch (bestSplit)
{
case k_X:
node.children.AddRange(splitLowX);
nodeComparer = m_NodeComparerX;
splitNode.children.AddRange(splitHighX);
splitNodeComparer = m_SplitNodeComparerX;
break;
case k_Y:
node.children.AddRange(splitLowY);
nodeComparer = m_NodeComparerY;
splitNode.children.AddRange(splitHighY);
splitNodeComparer = m_SplitNodeComparerY;
break;
case k_Z:
node.children.AddRange(splitLowZ);
nodeComparer = m_NodeComparerZ;
splitNode.children.AddRange(splitHighZ);
splitNodeComparer = m_SplitNodeComparerZ;
break;
}
// if a node has too few children, sort them by distance from split axis and get ready for next step
if (node.children.Count < m_MinPerNode && nodeComparer != null)
{
node.children.Sort(nodeComparer);
smallNode = node;
bigNode = splitNode;
}
else if (splitNode.children.Count < m_MinPerNode && splitNodeComparer != null)
{
splitNode.children.Sort(splitNodeComparer);
smallNode = splitNode;
bigNode = node;
}
// move closest children from big node to small node until small node has the minimum amount required
if (smallNode != null && bigNode != null)
{
var amount = m_MinPerNode - smallNode.children.Count;
var index = bigNode.children.Count - amount;
smallNode.children.AddRange(bigNode.children.GetRange(index, amount));
bigNode.children.RemoveRange(index, amount);
}
node.AdjustBounds();
splitNode.AdjustBounds();
foreach (var child in splitNode.children)
{
if (child is SpatialNode childNode)
{
childNode.parent = splitNode;
}
}
}
static int FindClosestCornerIndex(SpatialNode node, ISpatialObject obj)
{
return((obj.center.x <= node.center.x ? 0 : k_X) +
(obj.center.y <= node.center.y ? 0 : k_Y) +
(obj.center.z <= node.center.z ? 0 : k_Z));
}
void SplitNode(SpatialNode node, ISpatialObject obj, out SpatialNode splitNode)
{
CornerBasedSplit(node, obj, out splitNode);
}