/**
* Recursively create a BSP tree for a given set of points
* */
public static BspTreeNode CreateBspTree(BspTreeNode parentNode, List <Vector3> allPoints, List <int> pointIndices)
{
if (pointIndices.Count == 1)
{
InsertNode(parentNode, allPoints, pointIndices[0]);
}
else if (pointIndices.Count == 2)
{
// Two nodes - create separating plane
BspTreeNode node = new BspTreeNode();
Vector3 p0 = allPoints[pointIndices[0]];
Vector3 p1 = allPoints[pointIndices[1]];
node.P = Vector3.Multiply(Vector3.Add(p0, p1), 0.5f);
node.N = Vector3.Subtract(p0, p1).Normalized();
InsertNode(node, allPoints, pointIndices[0]);
InsertNode(node, allPoints, pointIndices[1]);
return(node);
}
else
{
// PCA-based separation
BspTreeNode node = new BspTreeNode();
PrincipalComponentAnalysis pca = new PrincipalComponentAnalysis();
foreach (int index in pointIndices)
{
pca.Add(allPoints[index]);
}
pca.applyPCA();
node.P = pca.getCentroid();
node.N = pca.getEigenVector(2);
// Handle children
List <int> pos = new List <int>();
List <int> neg = new List <int>();
foreach (int index in pointIndices)
{
if (node.IsPositive(allPoints[index]))
{
pos.Add(index);
}
else
{
neg.Add(index);
}
}
node.SetChild(BspTreeNode.Orientation.POSITIVE, CreateBspTree(node, allPoints, pos));
node.SetChild(BspTreeNode.Orientation.NEGATIVE, CreateBspTree(node, allPoints, neg));
return(node);
}
return(null);
}
private static void InsertNode(BspTreeNode node, List <Vector3> allPoints, int pointIndex)
{
if (node.IsPositive(allPoints[pointIndex]))
{
node.AddElement(BspTreeNode.Orientation.POSITIVE, pointIndex);
}
else
{
node.AddElement(BspTreeNode.Orientation.NEGATIVE, pointIndex);
}
}
public static List <int> GetBackToFront(BspTreeNode node, List <Vector3> points, Vector3 eye)
{
if (node == null)
{
return(new List <int>());
}
if (node.IsPositive(eye))
{
List <int> l1 = GetBackToFrontElements(node, BspTreeNode.Orientation.NEGATIVE, points, eye);
List <int> l2 = GetBackToFrontElements(node, BspTreeNode.Orientation.POSITIVE, points, eye);
l1.AddRange(l2);
return(l1);
}
else
{
List <int> l1 = GetBackToFrontElements(node, BspTreeNode.Orientation.POSITIVE, points, eye);
List <int> l2 = GetBackToFrontElements(node, BspTreeNode.Orientation.NEGATIVE, points, eye);
l1.AddRange(l2);
return(l1);
}
}
