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fix: Cleans up AI Pathfinding code to make it more portable for custom requirements. (#2474)

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Kamron Batman 2026-06-07 13:25:10 -07:00 • committed by GitHub
parent 412a71dfe0
commit 30fec7da26
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16 changed files with 198 additions and 102 deletions
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72
Projects/UOContent/Engines/Pathing/BitmapAStarAlgorithm.cs
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@ -23,7 +23,7 @@ using Server.Systems.FeatureFlags;
using CalcMoves = Server.Movement.Movement;
using MoveImpl = Server.Movement.MovementImpl;
namespace Server.PathAlgorithms.BitmapAStar;
namespace Server.PathAlgorithms;
/// <summary>
/// A* pathfinder with a single bitmap-cache lookup per cell expansion. Default walkers
@ -43,7 +43,6 @@ public class BitmapAStarAlgorithm : PathAlgorithm
public int z;
}
private const int MaxDepth = 300;
private const int AreaSize = 38;
private const int NodeCount = AreaSize * AreaSize * PlaneCount;
@ -51,38 +50,66 @@ public class BitmapAStarAlgorithm : PathAlgorithm
private const int PlaneOffset = 128;
private const int PlaneCount = 13;
private const int PlaneHeight = 20;
public static readonly PathAlgorithm Instance = new BitmapAStarAlgorithm();
// Default shared singleton (MaxSearchNodes = 1000, set from config in Configure). Typed
// as the concrete class so Configure can set its instance config; assignable anywhere a
// PathAlgorithm is expected. Specialized variants are just additional instances.
public static readonly BitmapAStarAlgorithm Instance = new();
private static readonly Direction[] _path = new Direction[AreaSize * AreaSize];
private static readonly PathNode[] _nodes = new PathNode[NodeCount];
private static readonly byte[] _nodeStates = new byte[NodeCount];
private static readonly int[] _successors = new int[8];
private static readonly PriorityQueue<int, int> _openQueue = new();
// Scratch buffers — reused across every Find on THIS instance. Per-instance (not static)
// so independently-configured algorithms don't share state. ~320 KB per instance; create
// specialized instances once (static readonly), never per-call. Safe to reuse per Find
// because the game loop is single-threaded and Find is never re-entered.
private readonly Direction[] _path = new Direction[AreaSize * AreaSize];
private readonly PathNode[] _nodes = new PathNode[NodeCount];
private readonly byte[] _nodeStates = new byte[NodeCount];
private readonly int[] _successors = new int[8];
private readonly PriorityQueue<int, int> _openQueue = new();
private static int _xOffset;
private static int _yOffset;
// A* node-expansion budget: the search bails (returning null) after this many node
// expansions. Benchmarked as near-optimal: above the ~500 needed to solve walled-off
// indoor routes, below the ~1500 window-exhaustion cost ceiling where a failed
// (unreachable) search's worst-case cost spikes for no solving benefit. Successful
// searches terminate on goal-found, so this never touches the common open-terrain case.
// Per-instance so specialized algorithms (e.g. a wider-budget variant for special NPCs)
// can coexist; the shared default lives on Instance and is set from config in Configure.
public int MaxSearchNodes { get; set; } = 1000;
private int _xOffset;
private int _yOffset;
// When set, GetSuccessors delegates to the per-cell slow path on every expansion
// (creature has CanFly — Z-jumping is beyond the cache's static-only scope).
private static bool _currentMobileNeedsSlowPath;
private bool _currentMobileNeedsSlowPath;
// When set, diagonal corner-cut uses the strict AND-rule (BOTH cardinal partners
// must be walkable) instead of the lenient creature OR-rule. Cache still applies —
// partner bits live in the same source-cell mask byte. Non-GM players only.
private static bool _currentMobilePlayerStrict;
private bool _currentMobilePlayerStrict;
// Capability overlay applied to cache results. Layered each cell:
// effective = (walkMask & !cantWalk) | (wetMask & canSwim)
// Reset at end of Find.
private static bool _currentMobileCanSwim;
private static bool _currentMobileCantWalk;
private bool _currentMobileCanSwim;
private bool _currentMobileCantWalk;
// Dynamic-obstacle pass capability flags (per-mobile, captured in Find).
// Mirrors MovementImpl.Check's per-mobile derivations so per-cell items/mobiles
// checks can be evaluated without re-deriving.
private static bool _currentMobileIgnoreDoors;
private static bool _currentMobileIgnoreSpellFields;
private static bool _currentMobileIgnoreMovableImpassables;
private bool _currentMobileIgnoreDoors;
private bool _currentMobileIgnoreSpellFields;
private bool _currentMobileIgnoreMovableImpassables;
public static void Configure()
{
// A* node-expansion budget. Default 1000 is benchmarked near-optimal (see
// MaxSearchNodes). Applied to the shared singleton; specialized instances pass their
// own value. Written back to server.cfg on first boot. Auto-invoked at startup via
// AssemblyHandler.Invoke("Configure").
Instance.MaxSearchNodes = ServerConfiguration.GetOrUpdateSetting(
"pathfinding.maxSearchNodes",
1000
);
}
private Point3D _goal;
@ -133,6 +160,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
_currentMobileIgnoreDoors = false;
_currentMobileIgnoreMovableImpassables = false;
}
// Mirrors MovementImpl: dead/spectral mobiles also ignore doors.
_currentMobileIgnoreDoors |= !m.Alive || m.Body.BodyID == 0x3DB || m.IsDeadBondedPet;
_currentMobileIgnoreSpellFields = m is PlayerMobile && map != Map.Felucca;
@ -163,7 +191,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
while (_openQueue.Count > 0)
{
if (++depth > MaxDepth)
if (++depth > MaxSearchNodes)
{
break;
}
@ -287,7 +315,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
return null;
}
private static int GetIndex(int x, int y, int z)
private int GetIndex(int x, int y, int z)
{
x -= _xOffset;
y -= _yOffset;
@ -304,7 +332,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
/// On cache fallthrough or for non-default walkers, defers to
/// <see cref="GetSuccessorsSlowPath"/> for THIS cell only.
/// </summary>
private static int GetSuccessors(int p, Mobile m, Map map)
private int GetSuccessors(int p, Mobile m, Map map)
{
var px = p % AreaSize;
var py = p / AreaSize % AreaSize;
@ -427,7 +455,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
/// non-Felucca players → ignore spell fields). Mobiles: any other mobile whose Z range
/// overlaps and which we can't move over.
/// </summary>
private static bool IsBlockedByDynamic(Mobile m, Map map, int x, int y, int z)
private bool IsBlockedByDynamic(Mobile m, Map map, int x, int y, int z)
{
var ourTop = z + PersonHeightConst;
@ -504,7 +532,7 @@ public class BitmapAStarAlgorithm : PathAlgorithm
/// CheckMovement validates land/statics/items via MovementImpl; dynamic mobile blocking
/// is layered on top because MovementImpl doesn't iterate same-cell mobiles.
/// </summary>
private static int GetSuccessorsSlowPath(Mobile m, Map map, int px, int py, Point3D p3D, int[] vals)
private int GetSuccessorsSlowPath(Mobile m, Map map, int px, int py, Point3D p3D, int[] vals)
{
var count = 0;