MoonTools.Bonk/Bonk/BroadPhase/SpatialHash.cs

136 lines
4.7 KiB
C#

using System;
using System.Collections.Generic;
using System.Numerics;
using MoonTools.Core.Structs;
namespace MoonTools.Core.Bonk
{
/// <summary>
/// Used to quickly check if two shapes are potentially overlapping.
/// </summary>
/// <typeparam name="T">The type that will be used to uniquely identify shape-transform pairs.</typeparam>
public class SpatialHash<T> where T : IEquatable<T>
{
private readonly int cellSize;
private readonly Dictionary<long, HashSet<T>> hashDictionary = new Dictionary<long, HashSet<T>>();
private readonly Dictionary<T, (IHasAABB2D, Transform2D)> IDLookup = new Dictionary<T, (IHasAABB2D, Transform2D)>();
public SpatialHash(int cellSize)
{
this.cellSize = cellSize;
}
private (int, int) Hash(Vector2 position)
{
return ((int)Math.Floor(position.X / cellSize), (int)Math.Floor(position.Y / cellSize));
}
/// <summary>
/// Inserts an element into the SpatialHash.
/// </summary>
/// <param name="id">A unique ID for the shape-transform pair.</param>
/// <param name="shape"></param>
/// <param name="transform2D"></param>
public void Insert(T id, IHasAABB2D shape, Transform2D transform2D)
{
var box = shape.TransformedAABB(transform2D);
var minHash = Hash(box.Min);
var maxHash = Hash(box.Max);
for (var i = minHash.Item1; i <= maxHash.Item1; i++)
{
for (var j = minHash.Item2; j <= maxHash.Item2; j++)
{
var key = MakeLong(i, j);
if (!hashDictionary.ContainsKey(key))
{
hashDictionary.Add(key, new HashSet<T>());
}
hashDictionary[key].Add(id);
IDLookup[id] = (shape, transform2D);
}
}
}
/// <summary>
/// Retrieves all the potential collisions of a shape-transform pair. Excludes any shape-transforms with the given ID.
/// </summary>
public IEnumerable<(T, IHasAABB2D, Transform2D)> Retrieve(T id, IHasAABB2D shape, Transform2D transform2D)
{
var box = shape.TransformedAABB(transform2D);
var minHash = Hash(box.Min);
var maxHash = Hash(box.Max);
for (var i = minHash.Item1; i <= maxHash.Item1; i++)
{
for (var j = minHash.Item2; j <= maxHash.Item2; j++)
{
var key = MakeLong(i, j);
if (hashDictionary.ContainsKey(key))
{
foreach (var t in hashDictionary[key])
{
var (otherShape, otherTransform) = IDLookup[t];
if (!id.Equals(t) && AABB.TestOverlap(box, otherShape.TransformedAABB(otherTransform)))
{
yield return (t, otherShape, otherTransform);
}
}
}
}
}
}
/// <summary>
/// Retrieves objects based on a pre-transformed AABB.
/// </summary>
/// <param name="aabb">A transformed AABB.</param>
/// <returns></returns>
public IEnumerable<(T, IHasAABB2D, Transform2D)> Retrieve(AABB aabb)
{
var minHash = Hash(aabb.Min);
var maxHash = Hash(aabb.Max);
for (var i = minHash.Item1; i <= maxHash.Item1; i++)
{
for (var j = minHash.Item2; j <= maxHash.Item2; j++)
{
var key = MakeLong(i, j);
if (hashDictionary.ContainsKey(key))
{
foreach (var t in hashDictionary[key])
{
var (otherShape, otherTransform) = IDLookup[t];
if (AABB.TestOverlap(aabb, otherShape.TransformedAABB(otherTransform)))
{
yield return (t, otherShape, otherTransform);
}
}
}
}
}
}
/// <summary>
/// Removes everything that has been inserted into the SpatialHash.
/// </summary>
public void Clear()
{
foreach (var hash in hashDictionary.Values)
{
hash.Clear();
}
IDLookup.Clear();
}
private static long MakeLong(int left, int right)
{
return ((long)left << 32) | ((uint)right);
}
}
}