public void Encapsulate(Aabb other)
{
min = Vector4.Min(min, other.min);
max = Vector4.Max(max, other.max);
}
public static BIHNode[] Build(ref IBounded[] elements, int maxDepth = 10, float maxOverlap = 0.7f)
{
List <BIHNode> nodes = new List <BIHNode> {
new BIHNode(0, elements.Length)
};
// auxiliar variables to keep track of current tree depth:
int depth = 0;
int nodesToNextLevel = 1;
var queue = new Queue <int>();
queue.Enqueue(0);
while (queue.Count > 0)
{
// get current node:
int index = queue.Dequeue();
var node = nodes[index];
// if this node contains enough elements, split it:
if (node.count > 2)
{
int start = node.start;
int end = start + (node.count - 1);
// calculate bounding box of all elements:
Aabb b = elements[start].GetBounds();
for (int k = start + 1; k <= end; ++k)
{
b.Encapsulate(elements[k].GetBounds());
}
// determine split axis (longest one):
Vector3 size = b.size;
int axis = node.axis = (size.x > size.y) ?
(size.x > size.z ? 0 : 2) :
(size.y > size.z ? 1 : 2);
// place split plane at half the longest axis:
float pivot = b.min[axis] + size[axis] * 0.5f;
// sort elements using the split plane (Hoare's partition algorithm):
int i = start - 1;
int j = end + 1;
Aabb bi, bj;
while (true)
{
// iterate over left elements, while they're smaller than the pivot.
do
{
bi = elements[++i].GetBounds();
if (bi.center[axis] < pivot)
{
node.min = Mathf.Max(node.min, bi.max[axis]);
}
} while (bi.center[axis] < pivot);
// iterate over right elements, while they're larger than the pivot.
do
{
bj = elements[--j].GetBounds();
if (bj.center[axis] >= pivot)
{
node.max = Mathf.Min(node.max, bj.min[axis]);
}
} while (bj.center[axis] >= pivot);
// if element i is larger than the pivot, j smaller than the pivot, swap them.
if (i < j)
{
ObiUtils.Swap(ref elements[i], ref elements[j]);
node.min = Mathf.Max(node.min, bj.max[axis]);
node.max = Mathf.Min(node.max, bi.min[axis]);
}
else
{
break;
}
}
// create two child nodes:
var minChild = new BIHNode(start, j - start + 1);
var maxChild = new BIHNode(j + 1, end - j);
// calculate child overlap:
float overlap = size[axis] > 0 ? Mathf.Max(node.min - node.max, 0) / size[axis] : 1;
// guard against cases where all elements are on one side of the split plane,
// due to all having the same or very similar bounds as the entire group.
if (overlap <= maxOverlap && minChild.count > 0 && maxChild.count > 0)
{
node.firstChild = nodes.Count;
nodes[index] = node;
queue.Enqueue(nodes.Count);
queue.Enqueue(nodes.Count + 1);
// append child nodes to list:
nodes.Add(minChild);
nodes.Add(maxChild);
}
// keep track of current depth:
if (--nodesToNextLevel == 0)
{
depth++;
if (depth >= maxDepth)
{
return(nodes.ToArray());
}
nodesToNextLevel = queue.Count;
}
}
}
return(nodes.ToArray());
}