/// <summary>
/// Initializes a new instance of the <see cref="TriangleQuadTree" /> class.
/// </summary>
/// <param name="mesh">Mesh containing triangles.</param>
/// <param name="maxDepth">The maximum depth of the tree.</param>
/// <param name="sizeBound">The maximum number of triangles contained in a leaf.</param>
/// <remarks>
/// The quadtree does not track changes of the mesh. If a mesh is refined or
/// changed in any other way, a new quadtree has to be built to make the point
/// location work.
///
/// A node of the tree will be split, if its level if less than the max depth parameter
/// AND the number of triangles in the node is greater than the size bound.
/// </remarks>
public TriangleQuadTree(Mesh mesh, int maxDepth = 10, int sizeBound = 10)
{
this.maxDepth = maxDepth;
this.sizeBound = sizeBound;
triangles = mesh.Triangles.ToArray();
int currentDepth = 0;
root = new QuadNode(mesh.Bounds, this, true);
root.CreateSubRegion(++currentDepth);
}
public void CreateSubRegion(int currentDepth)
{
// The four sub regions of the quad tree
// +--------------+
// | nw 2 | ne 3 |
// |------+pivot--|
// | sw 0 | se 1 |
// +--------------+
Rectangle box;
var width = bounds.Right - pivot.x;
var height = bounds.Top - pivot.y;
// 1. region south west
box = new Rectangle(bounds.Left, bounds.Bottom, width, height);
regions[0] = new QuadNode(box, tree);
// 2. region south east
box = new Rectangle(pivot.x, bounds.Bottom, width, height);
regions[1] = new QuadNode(box, tree);
// 3. region north west
box = new Rectangle(bounds.Left, pivot.y, width, height);
regions[2] = new QuadNode(box, tree);
// 4. region north east
box = new Rectangle(pivot.x, pivot.y, width, height);
regions[3] = new QuadNode(box, tree);
Point[] triangle = new Point[3];
// Find region for every triangle vertex
foreach (var index in triangles)
{
ITriangle tri = tree.triangles[index];
triangle[0] = tri.GetVertex(0);
triangle[1] = tri.GetVertex(1);
triangle[2] = tri.GetVertex(2);
AddTriangleToRegion(triangle, index);
}
for (int i = 0; i < 4; i++)
{
if (regions[i].triangles.Count > tree.sizeBound && currentDepth < tree.maxDepth)
{
regions[i].CreateSubRegion(currentDepth + 1);
}
}
}
public void CreateSubRegion(int currentDepth)
{
// The four sub regions of the quad tree
// +--------------+
// | nw | ne |
// |------+pivot--|
// | sw | se |
// +--------------+
BoundingBox box;
// 1. region south west
box = new BoundingBox(bounds.Xmin, bounds.Ymin, pivot.X, pivot.Y);
regions[0] = new QuadNode(box, tree);
// 2. region south east
box = new BoundingBox(pivot.X, bounds.Ymin, bounds.Xmax, pivot.Y);
regions[1] = new QuadNode(box, tree);
// 3. region north west
box = new BoundingBox(bounds.Xmin, pivot.Y, pivot.X, bounds.Ymax);
regions[2] = new QuadNode(box, tree);
// 4. region north east
box = new BoundingBox(pivot.X, pivot.Y, bounds.Xmax, bounds.Ymax);
regions[3] = new QuadNode(box, tree);
Point[] triangle = new Point[3];
// Find region for every triangle vertex
foreach (var index in triangles)
{
ITriangle tri = tree.triangles[index];
triangle[0] = tri.GetVertex(0);
triangle[1] = tri.GetVertex(1);
triangle[2] = tri.GetVertex(2);
AddTriangleToRegion(triangle, tri.ID);
}
for (int i = 0; i < 4; i++)
{
if (regions[i].triangles.Count > tree.sizeBound && currentDepth < tree.maxDepth)
{
regions[i].CreateSubRegion(currentDepth + 1);
}
}
}
