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using UnityEngine;
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using System;
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using System.Collections;
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using System.Collections.Generic;
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namespace Gaia
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{
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/// <summary>
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/// A region quadtree implementation used for fast lookup in a two dimensional world.
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/// </summary>
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/// <typeparam name="T">
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/// The type to store inside the tree.
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/// </typeparam>
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/// <remarks>
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/// This implementation is not thread-safe.
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/// </remarks>
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public class Quadtree<T>
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{
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/// <summary>
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/// The maximum number of nodes per tree.
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/// </summary>
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private readonly int nodeCapacity = 32;
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/// <summary>
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/// The nodes inside this region.
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/// </summary>
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private readonly List<QuadtreeNode> nodes;
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/// <summary>
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/// The child trees inside this region.
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/// </summary>
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private Quadtree<T>[] children;
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/// <summary>
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/// The boundaries of this region.
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/// </summary>
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private Rect boundaries;
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/// <summary>
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/// Gets the number of values inside this tree.
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/// </summary>
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public int Count
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{
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get;
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private set;
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="T:Quadtree`1"/> class.
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/// </summary>
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/// <param name="boundaries">
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/// The boundaries of the region.
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/// </param>
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/// <param name="nodeCapacity">
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/// The maximum number of nodes per tree.
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/// If the amount of nodes exceeds the tree will be subdivided into 4 sub trees.
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/// A value of 32 seems fine in terms of insert and remove speed.
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/// A value greater than 32 improves insert speed but slows down remove speed.
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/// </param>
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public Quadtree(Rect boundaries, int nodeCapacity = 32)
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{
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this.boundaries = boundaries;
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this.nodeCapacity = nodeCapacity;
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this.nodes = new List<QuadtreeNode>(nodeCapacity);
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}
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/// <summary>
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/// Inserts a value into the region.
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/// </summary>
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/// <param name="x">
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/// The X component of the value's position.
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/// </param>
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/// <param name="y">
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/// The y component of the value's position.
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/// </param>
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/// <param name="value">
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/// The value to insert.
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/// </param>
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/// <returns>
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/// true if the value was inserted into the region;
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/// false if the value's position was outside the region.
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/// </returns>
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public bool Insert(float x, float y, T value)
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{
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var position = new Vector2(x, y);
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var node = new QuadtreeNode(position, value);
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return this.Insert(node);
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}
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/// <summary>
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/// Inserts a value into the region.
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/// </summary>
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/// <param name="position">
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/// The position of the value.
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/// </param>
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/// <param name="value">
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/// The value to insert.
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/// </param>
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/// <returns>
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/// true if the value was inserted into the region;
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/// false if the value's position was outside the region.
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/// </returns>
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public bool Insert(Vector2 position, T value)
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{
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var node = new QuadtreeNode(position, value);
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return this.Insert(node);
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}
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/// <summary>
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/// Inserts a node into the region.
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/// </summary>
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/// <param name="node">
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/// The node to insert.
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/// </param>
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/// <returns>
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/// true if the node was inserted into the region;
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/// false if the position of the node was outside the region.
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/// </returns>
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private bool Insert(QuadtreeNode node)
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{
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if (!this.boundaries.Contains(node.Position))
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{
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return false;
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}
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if (this.children != null)
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{
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Quadtree<T> child;
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if (node.Position.y < this.children[2].boundaries.yMin)
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{
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if (node.Position.x < this.children[1].boundaries.xMin)
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{
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child = this.children[0];
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}
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else
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{
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child = this.children[1];
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}
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}
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else
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{
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if (node.Position.x < this.children[1].boundaries.xMin)
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{
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child = this.children[2];
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}
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else
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{
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child = this.children[3];
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}
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}
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if (child.Insert(node))
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{
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this.Count++;
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return true;
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}
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}
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if (this.nodes.Count < this.nodeCapacity)
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{
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this.nodes.Add(node);
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this.Count++;
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return true;
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}
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this.Subdivide();
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return this.Insert(node);
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}
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/// <summary>
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/// Returns the values that are within the specified <paramref name="range"/>.
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/// </summary>
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/// <param name="range">
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/// A rectangle representing the region to query.
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/// </param>
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/// <returns>
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/// Any value found inside the specified <paramref name="range"/>.
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/// </returns>
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public IEnumerable<T> Find(Rect range)
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{
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if (this.Count == 0)
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{
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yield break;
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}
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var rangexMax = range.xMax;
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var rangexMin = range.xMin;
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var rangeyMax = range.yMax;
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var rangeyMin = range.yMin;
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if (!(
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this.boundaries.xMin < rangexMax &&
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this.boundaries.xMax > rangexMin &&
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this.boundaries.yMin < rangeyMax &&
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this.boundaries.yMax > rangeyMin
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))
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{
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yield break;
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}
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if (this.children == null)
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{
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for (var index = 0; index < this.nodes.Count; index++)
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{
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var node = this.nodes[index];
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if (
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node.Position.x >= rangexMin &&
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node.Position.x <= rangexMax &&
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node.Position.y >= rangeyMin &&
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node.Position.y <= rangeyMax
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)
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{
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yield return node.Value;
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}
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}
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}
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else
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{
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for (var index = 0; index < this.children.Length; index++)
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{
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var child = this.children[index];
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foreach (var value in child.Find(range))
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{
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yield return value;
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}
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}
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}
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}
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/// <summary>
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/// Removes a value from the region.
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/// </summary>
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/// <param name="x">
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/// The X component of the value's position.
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/// </param>
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/// <param name="z">
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/// The Z component of the value's position.
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/// </param>
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/// <param name="value">
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/// The value to remove.
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/// </param>
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/// <returns>
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/// true if the value was removed from the region;
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/// false if the value's position was outside the region.
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/// </returns>
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public bool Remove(float x, float z, T value)
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{
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return this.Remove(new Vector2(x, z), value);
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}
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/// <summary>
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/// Removes a value from the region.
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/// </summary>
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/// <param name="position">
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/// The position of the value.
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/// </param>
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/// <param name="value">
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/// The value to remove.
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/// </param>
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/// <returns>
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/// true if the value was removed from the region;
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/// false if the value's position was outside the region.
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/// </returns>
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public bool Remove(Vector2 position, T value)
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{
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if (this.Count == 0)
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{
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return false;
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}
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if (!this.boundaries.Contains(position))
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{
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return false;
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}
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if (this.children != null)
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{
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var isRemoved = false;
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Quadtree<T> child;
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if (position.y < this.children[2].boundaries.yMin)
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{
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if (position.x < this.children[1].boundaries.xMin)
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{
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child = this.children[0];
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}
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else
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{
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child = this.children[1];
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}
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}
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else
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{
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if (position.x < this.children[1].boundaries.xMin)
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{
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child = this.children[2];
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}
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else
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{
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child = this.children[3];
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}
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}
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if (child.Remove(position, value))
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{
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isRemoved = true;
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this.Count--;
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}
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if (this.Count <= this.nodeCapacity)
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{
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this.Combine();
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}
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return isRemoved;
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}
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for (var index = 0; index < this.nodes.Count; index++)
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{
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var node = this.nodes[index];
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if (node.Position.Equals(position))
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{
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this.nodes.RemoveAt(index);
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this.Count--;
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return true;
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}
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}
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return false;
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}
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/// <summary>
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/// Splits the region into 4 new subregions and moves the existing values into the new subregions.
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/// </summary>
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private void Subdivide()
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{
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this.children = new Quadtree<T>[4];
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var width = this.boundaries.width * 0.5f;
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var height = this.boundaries.height * 0.5f;
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for (var index = 0; index < this.children.Length; index++)
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{
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var boundaries = new Rect(
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this.boundaries.xMin + width * (index % 2),
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this.boundaries.yMin + height * (index / 2),
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width,
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height
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);
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this.children[index] = new Quadtree<T>(boundaries);
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}
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this.Count = 0;
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for (var index = 0; index < this.nodes.Count; index++)
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{
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var node = this.nodes[index];
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this.Insert(node);
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}
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this.nodes.Clear();
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}
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/// <summary>
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/// Joins the contents of the children into this region and remove the child regions.
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/// </summary>
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private void Combine()
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{
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for (var index = 0; index < this.children.Length; index++)
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{
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var child = this.children[index];
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this.nodes.AddRange(child.nodes);
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}
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this.children = null;
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}
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/// <summary>
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/// A single node inside a quadtree used for keeping values and their position.
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/// </summary>
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private class QuadtreeNode
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{
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/// <summary>
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/// Gets the position of the value.
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/// </summary>
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public Vector2 Position
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{
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get;
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private set;
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}
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/// <summary>
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/// Gets the value.
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/// </summary>
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public T Value
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{
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get;
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private set;
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="T:QuadtreeNode"/> class.
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/// </summary>
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/// <param name="position">
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/// The position of the value.
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/// </param>
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/// <param name="value">
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/// The value.
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/// </param>
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public QuadtreeNode(Vector2 position, T value)
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{
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this.Position = position;
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this.Value = value;
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}
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}
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}
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}
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