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Added the ability to find paths to one of multiple goals using AStar

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Ell 2022-10-10 11:31:23 +02:00
parent d3b153fd45
commit d6309ce9c1
3 changed files with 24 additions and 9 deletions
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3
CHANGELOG.md
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@ -14,13 +14,14 @@ Jump to version:
### MLEM
Additions
- Added TokenizedString.Realign
- **Added the ability to find paths to one of multiple goals using AStar**
Improvements
- Improved EnumHelper.GetValues signature to return an array
- Allow using external gesture handling alongside InputHandler through ExternalGestureHandling
- Discard old data when updating a StaticSpriteBatch
- Multi-target net452, making MLEM compatible with MonoGame for consoles
- **Allow retrieving the cost of a calculated path when using AStar**
- Allow retrieving the cost of a calculated path when using AStar
- **Drastically improved StaticSpriteBatch batching performance**
Fixes

19
MLEM/Pathfinding/AStar.cs
View file

@ -61,7 +61,7 @@ namespace MLEM.Pathfinding {
/// <param name="additionalNeighbors">A function that determines a set of additional neighbors to be considered for a given point.</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, CollectAdditionalNeighbors additionalNeighbors = null) {
this.TryFindPath(start, goal, out var path, out _, costFunction, defaultCost, maxTries, additionalNeighbors);
this.TryFindPath(start, new[] {goal}, out var path, out _, costFunction, defaultCost, maxTries, additionalNeighbors);
return path;
}
@ -69,7 +69,7 @@ namespace MLEM.Pathfinding {
/// Tries to find a path between two points using this pathfinder's default settings or, alternatively, the supplied override settings.
/// </summary>
/// <param name="start">The point to start path finding at</param>
/// <param name="goal">The point to find a path to</param>
/// <param name="goals">The points to find a path to, one of which will be chosen as the closest or best destination</param>
/// <param name="path">The path that was found, or <see langword="null"/> if no path was found.</param>
/// <param name="totalCost">The total cost that was calculated for the path, or <see cref="float.PositiveInfinity"/> if no path was found.</param>
/// <param name="costFunction">The function that determines the cost for each path point</param>
@ -77,7 +77,7 @@ namespace MLEM.Pathfinding {
/// <param name="maxTries">The maximum amount of tries before path finding is aborted</param>
/// <param name="additionalNeighbors">A function that determines a set of additional neighbors to be considered for a given point.</param>
/// <returns>Whether a path was found.</returns>
public bool TryFindPath(T start, T goal, out Stack<T> path, out float totalCost, GetCost costFunction = null, float? defaultCost = null, int? maxTries = null, CollectAdditionalNeighbors additionalNeighbors = null) {
public bool TryFindPath(T start, ICollection<T> goals, out Stack<T> path, out float totalCost, GetCost costFunction = null, float? defaultCost = null, int? maxTries = null, CollectAdditionalNeighbors additionalNeighbors = null) {
path = null;
totalCost = float.PositiveInfinity;
@ -90,7 +90,7 @@ namespace MLEM.Pathfinding {
var neighbors = new HashSet<T>();
var open = new Dictionary<T, PathPoint<T>>();
var closed = new Dictionary<T, PathPoint<T>>();
open.Add(start, new PathPoint<T>(start, this.GetHeuristicDistance(start, goal), null, 0, defCost));
open.Add(start, new PathPoint<T>(start, this.GetMinHeuristicDistance(start, goals), null, 0, defCost));
var count = 0;
while (open.Count > 0) {
@ -105,7 +105,7 @@ namespace MLEM.Pathfinding {
open.Remove(current.Pos);
closed.Add(current.Pos, current);
if (EqualityComparer<T>.Default.Equals(current.Pos, goal)) {
if (goals.Contains(current.Pos)) {
path = AStar<T>.CompilePath(current);
totalCost = current.F;
break;
@ -118,7 +118,7 @@ namespace MLEM.Pathfinding {
foreach (var neighborPos in neighbors) {
var cost = getCost(current.Pos, neighborPos);
if (!float.IsPositiveInfinity(cost) && cost < float.MaxValue && !closed.ContainsKey(neighborPos)) {
var neighbor = new PathPoint<T>(neighborPos, this.GetHeuristicDistance(neighborPos, goal), current, cost, defCost);
var neighbor = new PathPoint<T>(neighborPos, this.GetMinHeuristicDistance(neighborPos, goals), 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) {
@ -160,6 +160,13 @@ namespace MLEM.Pathfinding {
/// <param name="neighbors">The set to populate with neighbors.</param>
protected abstract void CollectNeighbors(T position, ISet<T> neighbors);
private float GetMinHeuristicDistance(T start, IEnumerable<T> positions) {
var min = float.MaxValue;
foreach (var position in positions)
min = Math.Min(min, this.GetHeuristicDistance(start, position));
return min;
}
private static Stack<T> CompilePath(PathPoint<T> current) {
var path = new Stack<T>();
while (current != null) {

11
Tests/PathfindingTests.cs
View file

@ -83,7 +83,7 @@ namespace Tests {
}
[Test]
public void TestCosts() {
public void TestCostsAndMultipleGoals() {
var area = new[] {
"XXXXXXXX",
"X 2 X",
@ -95,12 +95,19 @@ namespace Tests {
};
var pathfinder = PathfindingTests.CreatePathfinder(area, false);
// try to find paths to each goal individually
var goals = new[] {new Point(1, 5), new Point(3, 5), new Point(5, 5)};
var goalCosts = new[] {19, float.PositiveInfinity, 9};
for (var i = 0; i < goals.Length; i++) {
pathfinder.TryFindPath(new Point(1, 1), goals[i], out _, out var cost);
pathfinder.TryFindPath(new Point(1, 1), new[] {goals[i]}, out _, out var cost);
Assert.AreEqual(goalCosts[i], cost);
}
// try to find paths to the best goal
var expected = new[] {new Point(1, 1), new Point(2, 1), new Point(3, 1), new Point(4, 1), new Point(5, 1), new Point(5, 2), new Point(5, 3), new Point(5, 4), new Point(5, 5)};
pathfinder.TryFindPath(new Point(1, 1), goals, out var path, out var bestCost);
Assert.AreEqual(bestCost, 9);
Assert.AreEqual(expected, path);
}
private static Stack<Point> FindPathInArea(Point start, Point end, IEnumerable<string> area, bool allowDiagonals, AStar2.CollectAdditionalNeighbors collectAdditionalNeighbors = null) {