using System.Collections.Generic;
using UnityEngine;
// A Dynamic Octree for storing any objects that can be described as a single point
// See also: BoundsOctree, where objects are described by AABB bounds
// Octree: An octree is a tree data structure which divides 3D space into smaller partitions (nodes)
// and places objects into the appropriate nodes. This allows fast access to objects
// in an area of interest without having to check every object.
// Dynamic: The octree grows or shrinks as required when objects as added or removed
// It also splits and merges nodes as appropriate. There is no maximum depth.
// Nodes have a constant - numObjectsAllowed - which sets the amount of items allowed in a node before it splits.
// T: The content of the octree can be anything, since the bounds data is supplied separately.
// Originally written for my game Scraps (http://www.scrapsgame.com) but intended to be general-purpose.
// Copyright 2014 Nition, BSD licence (see LICENCE file). http://nition.co
// Unity-based, but could be adapted to work in pure C#
namespace AwesomeTechnologies.External.Octree
{
public class PointOctree<T> where T : class
{
// The total amount of objects currently in the tree
public int Count { get; private set; }
// Root node of the octree
PointOctreeNode<T> rootNode;
// Size that the octree was on creation
readonly float initialSize;
// Minimum side length that a node can be - essentially an alternative to having a max depth
readonly float minSize;
/// <summary>
/// Constructor for the point octree.
/// </summary>
/// <param name="initialWorldSize">Size of the sides of the initial node. The octree will never shrink smaller than this.</param>
/// <param name="initialWorldPos">Position of the centre of the initial node.</param>
/// <param name="minNodeSize">Nodes will stop splitting if the new nodes would be smaller than this.</param>
public PointOctree(float initialWorldSize, Vector3 initialWorldPos, float minNodeSize)
{
if (minNodeSize > initialWorldSize)
{
Debug.LogWarning("Minimum node size must be at least as big as the initial world size. Was: " +
minNodeSize + " Adjusted to: " + initialWorldSize);
minNodeSize = initialWorldSize;
}
Count = 0;
initialSize = initialWorldSize;
minSize = minNodeSize;
rootNode = new PointOctreeNode<T>(initialSize, minSize, initialWorldPos);
}
// #### PUBLIC METHODS ####
/// <summary>
/// Add an object.
/// </summary>
/// <param name="obj">Object to add.</param>
/// <param name="objPos">Position of the object.</param>
public void Add(T obj, Vector3 objPos)
{
// Add object or expand the octree until it can be added
int count = 0; // Safety check against infinite/excessive growth
while (!rootNode.Add(obj, objPos))
{
Grow(objPos - rootNode.Center);
if (++count > 20)
{
Debug.LogError("Aborted Add operation as it seemed to be going on forever (" + (count - 1) +
") attempts at growing the octree.");
return;
}
}
Count++;
}
/// <summary>
/// Remove an object. Makes the assumption that the object only exists once in the tree.
/// </summary>
/// <param name="obj">Object to remove.</param>
/// <returns>True if the object was removed successfully.</returns>
public bool Remove(T obj)
{
bool removed = rootNode.Remove(obj);
// See if we can shrink the octree down now that we've removed the item
if (removed)
{
Count--;
Shrink();
}
return removed;
}
/// <summary>
/// Removes the specified object at the given position. Makes the assumption that the object only exists once in the tree.
/// </summary>
/// <param name="obj">Object to remove.</param>
/// <param name="objPos">Position of the object.</param>
/// <returns>True if the object was removed successfully.</returns>
public bool Remove(T obj, Vector3 objPos)
{
bool removed = rootNode.Remove(obj, objPos);
// See if we can shrink the octree down now that we've removed the item
if (removed)
{
Count--;
Shrink();
}
return removed;
}
/// <summary>
/// Returns objects that are within maxDistance of the specified ray.
/// If none returns false. Uses supplied list for results.
/// </summary>
/// <param name="ray">The ray. Passing as ref to improve performance since it won't have to be copied.</param>
/// <param name="maxDistance">Maximum distance from the ray to consider</param>
/// <param name="nearBy">Pre-initialized list to populate</param>
/// <returns>True if items are found, false if not</returns>
public bool GetNearbyNonAlloc(Ray ray, float maxDistance, List<T> nearBy)
{
nearBy.Clear();
rootNode.GetNearby(ref ray, ref maxDistance, nearBy);
if (nearBy.Count > 0)
return true;
return false;
}
/// <summary>
/// Return objects that are within maxDistance of the specified ray.
/// If none, returns an empty array (not null).
/// </summary>
/// <param name="ray">The ray. Passing as ref to improve performance since it won't have to be copied.</param>
/// <param name="maxDistance">Maximum distance from the ray to consider.</param>
/// <returns>Objects within range.</returns>
public T[] GetNearby(Ray ray, float maxDistance)
{
List<T> collidingWith = new List<T>();
rootNode.GetNearby(ref ray, ref maxDistance, collidingWith);
return collidingWith.ToArray();
}
/// <summary>
/// Return objects that are within <paramref name="maxDistance"/> of the specified position.
/// If none, returns an empty array (not null).
/// </summary>
/// <param name="position">The position. Passing as ref to improve performance since it won't have to be copied.</param>
/// <param name="maxDistance">Maximum distance from the ray to consider.</param>
/// <returns>Objects within range.</returns>
public T[] GetNearby(Vector3 position, float maxDistance)
{
List<T> collidingWith = new List<T>();
rootNode.GetNearby(ref position, ref maxDistance, collidingWith);
return collidingWith.ToArray();
}
/// <summary>
/// Return all objects in the tree.
/// If none, returns an empty array (not null).
/// </summary>
/// <returns>All objects.</returns>
public ICollection<T> GetAll()
{
List<T> objects = new List<T>(Count);
rootNode.GetAll(objects);
return objects;
}
/// <summary>
/// Draws node boundaries visually for debugging.
/// Must be called from OnDrawGizmos externally. See also: DrawAllObjects.
/// </summary>
public void DrawAllBounds()
{
rootNode.DrawAllBounds();
}
/// <summary>
/// Draws the bounds of all objects in the tree visually for debugging.
/// Must be called from OnDrawGizmos externally. See also: DrawAllBounds.
/// </summary>
public void DrawAllObjects()
{
rootNode.DrawAllObjects();
}
// #### PRIVATE METHODS ####
/// <summary>
/// Grow the octree to fit in all objects.
/// </summary>
/// <param name="direction">Direction to grow.</param>
void Grow(Vector3 direction)
{
int xDirection = direction.x >= 0 ? 1 : -1;
int yDirection = direction.y >= 0 ? 1 : -1;
int zDirection = direction.z >= 0 ? 1 : -1;
PointOctreeNode<T> oldRoot = rootNode;
float half = rootNode.SideLength / 2;
float newLength = rootNode.SideLength * 2;
Vector3 newCenter = rootNode.Center + new Vector3(xDirection * half, yDirection * half, zDirection * half);
// Create a new, bigger octree root node
rootNode = new PointOctreeNode<T>(newLength, minSize, newCenter);
// Create 7 new octree children to go with the old root as children of the new root
int rootPos = GetRootPosIndex(xDirection, yDirection, zDirection);
PointOctreeNode<T>[] children = new PointOctreeNode<T>[8];
for (int i = 0; i < 8; i++)
{
if (i == rootPos)
{
children[i] = oldRoot;
}
else
{
xDirection = i % 2 == 0 ? -1 : 1;
yDirection = i > 3 ? -1 : 1;
zDirection = (i < 2 || (i > 3 && i < 6)) ? -1 : 1;
children[i] = new PointOctreeNode<T>(rootNode.SideLength, minSize,
newCenter + new Vector3(xDirection * half, yDirection * half, zDirection * half));
}
}
// Attach the new children to the new root node
rootNode.SetChildren(children);
}
/// <summary>
/// Shrink the octree if possible, else leave it the same.
/// </summary>
void Shrink()
{
rootNode = rootNode.ShrinkIfPossible(initialSize);
}
/// <summary>
/// Used when growing the octree. Works out where the old root node would fit inside a new, larger root node.
/// </summary>
/// <param name="xDir">X direction of growth. 1 or -1.</param>
/// <param name="yDir">Y direction of growth. 1 or -1.</param>
/// <param name="zDir">Z direction of growth. 1 or -1.</param>
/// <returns>Octant where the root node should be.</returns>
static int GetRootPosIndex(int xDir, int yDir, int zDir)
{
int result = xDir > 0 ? 1 : 0;
if (yDir < 0) result += 4;
if (zDir > 0) result += 2;
return result;
}
}
}