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Added the ability to include special per-position directions in AStar pathfinding

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Ell 2022-10-09 20:07:38 +02:00
parent 2d3d93c610
commit bfa4ab4ac2
5 changed files with 71 additions and 26 deletions
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1
CHANGELOG.md
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@ -14,6 +14,7 @@ Jump to version:
### MLEM
Additions
- Added TokenizedString.Realign
- Added the ability to include special per-position directions in AStar pathfinding
Improvements
- Improved EnumHelper.GetValues signature to return an array

64
MLEM/Pathfinding/AStar.cs
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@ -16,6 +16,7 @@ namespace MLEM.Pathfinding {
/// </summary>
[Obsolete("This field is deprecated. Use float.PositiveInfinity or float.MaxValue instead.")]
public const float InfiniteCost = float.PositiveInfinity;
/// <summary>
/// The array of all directions that will be checked for path finding.
/// Note that this array is only used if <see cref="DefaultAllowDiagonals"/> is true.
@ -26,6 +27,7 @@ namespace MLEM.Pathfinding {
/// Note that this array is only used if <see cref="DefaultAllowDiagonals"/> is false.
/// </summary>
public readonly T[] AdjacentDirections;
/// <summary>
/// The default cost function that determines the cost for each path finding position.
/// </summary>
@ -42,6 +44,11 @@ namespace MLEM.Pathfinding {
/// Whether or not diagonal directions are considered while finding a path.
/// </summary>
public bool DefaultAllowDiagonals;
/// <summary>
/// The default function that determines a set of additional directions (or offsets) that should be tested for walkability, in addition to <see cref="AllDirections"/> or <see cref="AdjacentDirections"/>.
/// </summary>
public GetSpecialDirections DefaultSpecialDirections;
/// <summary>
/// The amount of tries required for finding the last queried path
/// </summary>
@ -60,13 +67,15 @@ namespace MLEM.Pathfinding {
/// <param name="defaultAllowDiagonals">Whether or not diagonals should be allowed by default</param>
/// <param name="defaultCost">The default cost for a path point</param>
/// <param name="defaultMaxTries">The default amount of tries before path finding is aborted</param>
protected AStar(T[] allDirections, T[] adjacentDirections, GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000) {
/// <param name="defaultSpecialDirections">The default function that determines a set of additional directions (or offsets) that should be tested for walkability.</param>
protected AStar(T[] allDirections, T[] adjacentDirections, GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000, GetSpecialDirections defaultSpecialDirections = null) {
this.AllDirections = allDirections;
this.AdjacentDirections = adjacentDirections;
this.DefaultCostFunction = defaultCostFunction;
this.DefaultCost = defaultCost;
this.DefaultMaxTries = defaultMaxTries;
this.DefaultAllowDiagonals = defaultAllowDiagonals;
this.DefaultSpecialDirections = defaultSpecialDirections;
}
/// <inheritdoc cref="FindPath"/>
@ -83,14 +92,16 @@ namespace MLEM.Pathfinding {
/// <param name="defaultCost">The default cost for each path point</param>
/// <param name="maxTries">The maximum amount of tries before path finding is aborted</param>
/// <param name="allowDiagonals">If diagonals should be looked at for path finding</param>
/// <param name="specialDirections">An optional function that determines a set of additional directions (or offsets) that should be tested for walkability.</param>
/// <returns>A stack of path points, where the top item is the first point to go to, or null if no path was found.</returns>
public Stack<T> FindPath(T start, T goal, GetCost costFunction = null, float? defaultCost = null, int? maxTries = null, bool? allowDiagonals = null) {
public Stack<T> FindPath(T start, T goal, GetCost costFunction = null, float? defaultCost = null, int? maxTries = null, bool? allowDiagonals = null, GetSpecialDirections specialDirections = null) {
var stopwatch = Stopwatch.StartNew();
var getCost = costFunction ?? this.DefaultCostFunction;
var diags = allowDiagonals ?? this.DefaultAllowDiagonals;
var tries = maxTries ?? this.DefaultMaxTries;
var defCost = defaultCost ?? this.DefaultCost;
var special = specialDirections ?? this.DefaultSpecialDirections;
var open = new Dictionary<T, PathPoint<T>>();
var closed = new Dictionary<T, PathPoint<T>>();
@ -115,24 +126,11 @@ namespace MLEM.Pathfinding {
break;
}
var dirsUsed = diags ? this.AllDirections : this.AdjacentDirections;
foreach (var dir in dirsUsed) {
var neighborPos = this.AddPositions(current.Pos, dir);
var cost = getCost(current.Pos, neighborPos);
if (!float.IsPositiveInfinity(cost) && cost < float.MaxValue && !closed.ContainsKey(neighborPos)) {
var neighbor = new PathPoint<T>(neighborPos, this.GetManhattanDistance(neighborPos, goal), current, cost, defCost);
// check if we already have a waypoint at this location with a worse path
if (open.TryGetValue(neighborPos, out var alreadyNeighbor)) {
if (neighbor.G < alreadyNeighbor.G) {
open.Remove(neighborPos);
} else {
// if the old waypoint is better, we don't add ours
continue;
}
}
// add the new neighbor as a possible waypoint
open.Add(neighborPos, neighbor);
}
foreach (var dir in diags ? this.AllDirections : this.AdjacentDirections)
ExamineDirection(current, dir);
if (special != null) {
foreach (var dir in special(current.Pos))
ExamineDirection(current, dir);
}
count++;
@ -144,6 +142,25 @@ namespace MLEM.Pathfinding {
this.LastTriesNeeded = count;
this.LastTimeNeeded = stopwatch.Elapsed;
return ret;
void ExamineDirection(PathPoint<T> current, T dir) {
var neighborPos = this.AddPositions(current.Pos, dir);
var cost = getCost(current.Pos, neighborPos);
if (!float.IsPositiveInfinity(cost) && cost < float.MaxValue && !closed.ContainsKey(neighborPos)) {
var neighbor = new PathPoint<T>(neighborPos, this.GetManhattanDistance(neighborPos, goal), current, cost, defCost);
// check if we already have a waypoint at this location with a worse path
if (open.TryGetValue(neighborPos, out var alreadyNeighbor)) {
if (neighbor.G < alreadyNeighbor.G) {
open.Remove(neighborPos);
} else {
// if the old waypoint is better, we don't add ours
return;
}
}
// add the new neighbor as a possible waypoint
open.Add(neighborPos, neighbor);
}
}
}
/// <summary>
@ -174,6 +191,13 @@ namespace MLEM.Pathfinding {
/// <param name="nextPos">The position we're trying to reach from the current position</param>
public delegate float GetCost(T currPos, T nextPos);
/// <summary>
/// A delegate used by <see cref="AStar{T}.DefaultSpecialDirections"/> and <see cref="AStar{T}.FindPath"/> that determines a set of additional directions (or offsets) that should be tested for walkability.
/// </summary>
/// <param name="currPos">The current position in the path.</param>
/// <returns>A set of additional directions (or offsets) that should be checked for walkability. If the given <paramref name="currPos"/> has no special directions, an empty <see cref="IEnumerable{T}"/> should be returned.</returns>
public delegate IEnumerable<T> GetSpecialDirections(T currPos);
}
/// <summary>

4
MLEM/Pathfinding/AStar2.cs
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@ -13,8 +13,8 @@ namespace MLEM.Pathfinding {
private static readonly Point[] AllDirs = Direction2Helper.All.Offsets().ToArray();
/// <inheritdoc />
public AStar2(GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000) :
base(AStar2.AllDirs, AStar2.AdjacentDirs, defaultCostFunction, defaultAllowDiagonals, defaultCost, defaultMaxTries) {}
public AStar2(GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000, GetSpecialDirections defaultSpecialDirections = null) :
base(AStar2.AllDirs, AStar2.AdjacentDirs, defaultCostFunction, defaultAllowDiagonals, defaultCost, defaultMaxTries, defaultSpecialDirections) {}
/// <inheritdoc />
protected override Point AddPositions(Point first, Point second) {

4
MLEM/Pathfinding/AStar3.cs
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@ -34,8 +34,8 @@ namespace MLEM.Pathfinding {
}
/// <inheritdoc />
public AStar3(GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000) :
base(AStar3.AllDirs, AStar3.AdjacentDirs, defaultCostFunction, defaultAllowDiagonals, defaultCost, defaultMaxTries) {}
public AStar3(GetCost defaultCostFunction, bool defaultAllowDiagonals, float defaultCost = 1, int defaultMaxTries = 10000, GetSpecialDirections defaultSpecialDirections = null) :
base(AStar3.AllDirs, AStar3.AdjacentDirs, defaultCostFunction, defaultAllowDiagonals, defaultCost, defaultMaxTries, defaultSpecialDirections) {}
/// <inheritdoc />
protected override Vector3 AddPositions(Vector3 first, Vector3 second) {

24
Tests/PathfindingTests.cs
View file

@ -60,13 +60,33 @@ namespace Tests {
Assert.IsNotNull(PathfindingTests.FindPathInArea(new Point(1, 1), new Point(2, 3), area, true));
}
private static Stack<Point> FindPathInArea(Point start, Point end, IEnumerable<string> area, bool allowDiagonals) {
[Test]
public void TestSpecialDirections() {
var area = new[] {
"XXXX",
"X XX",
"X X",
"XXXX",
"X X",
"XXXX"
};
// both types of traditional pathfinding should get stuck
Assert.IsNull(PathfindingTests.FindPathInArea(new Point(1, 1), new Point(2, 4), area, false));
Assert.IsNull(PathfindingTests.FindPathInArea(new Point(1, 1), new Point(2, 4), area, true));
// but if we define a link across the wall, it should work
Assert.IsNotNull(PathfindingTests.FindPathInArea(new Point(1, 1), new Point(2, 4), area, false,
p => p.X == 2 && p.Y == 2 ? new[] {new Point(-1, 2)} : Enumerable.Empty<Point>()));
}
private static Stack<Point> FindPathInArea(Point start, Point end, IEnumerable<string> area, bool allowDiagonals, AStar2.GetSpecialDirections getSpecialDirections = null) {
var costs = area.Select(s => s.Select(c => c switch {
' ' => 1,
'X' => float.PositiveInfinity,
_ => (float) char.GetNumericValue(c)
}).ToArray()).ToArray();
var pathFinder = new AStar2((_, p2) => costs[p2.Y][p2.X], allowDiagonals);
var pathFinder = new AStar2((_, p2) => costs[p2.Y][p2.X], allowDiagonals, 1, 64, getSpecialDirections);
return pathFinder.FindPath(start, end);
}