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