public AlignedBox3Tree(Vector3[] positions, UInt16[] indices)
{
Debug.Assert(indices.Length % 3 == 0);
this.positions = new Vector3[positions.Length];
Array.Copy(positions, this.positions, positions.Length);
this.indices = new UInt16[indices.Length];
Array.Copy(indices, this.indices, indices.Length);
root = new AlignedBox3TreeNode(this.indices.Length / 3, 0, this.indices, this.positions);
}
/// <summary>
/// recursively builds the collision tree. this method calculates the bounding box of the node
/// and if necessary splits the node into two and continues to build the tree within these child
/// nodes
/// constructs this node
/// </summary>
/// <param name="numTriangles">
/// Numbers of Triangles stored inside this node or inside its children
/// </param>
/// <param name="baseIndex">
/// Index into the indices array. This is the point where the part of the array that
/// is owned by this node starts
/// </param>
/// <param name="indices">
/// reference to the array containing all triangle indices of the model
/// </param>
public AlignedBox3TreeNode(int numTriangles, int baseIndex, UInt16[] indices, Vector3[] positions)
{
this.numTriangles = numTriangles;
this.baseIndex = baseIndex;
this.indices = indices;
Debug.Assert(numTriangles > 0);
if (numTriangles == 0)
{
return;
}
ComputeBoundingBox(positions);
if (numTriangles < 10)
{
return;
}
// split along the axis where we get triangles distributed the best...
int halfNumTriangles = numTriangles / 2;
int[] numLeft = new int[3] {
Split(positions, Axis.AxisX), Split(positions, Axis.AxisY), Split(positions, Axis.AxisZ)
};
int[] diff = new int[3] {
halfNumTriangles - numLeft[0], halfNumTriangles - numLeft[1], halfNumTriangles - numLeft[2]
};
int min = 0; // 0 == x-axis, 1 == y-axis, 2 == z-axis
Axis minAxis = Axis.AxisX;
if (System.Math.Abs(diff[1]) < System.Math.Abs(diff[min]))
{
min = 1; minAxis = Axis.AxisY;
}
if (System.Math.Abs(diff[2]) < System.Math.Abs(diff[min]))
{
min = 2; minAxis = Axis.AxisZ;
}
int splitCount = Split(positions, minAxis);
if (splitCount == 0 || splitCount == numTriangles)
{
// abort if either 0 or all triangles would be positioned inside a single child
return;
}
left = new AlignedBox3TreeNode(splitCount, baseIndex, indices, positions);
right = new AlignedBox3TreeNode(numTriangles - splitCount, baseIndex + splitCount * 3, indices, positions);
}