ModernUO/Projects/UOContent/Engines/Pathing/MovementPath.cs
Kamron Batman 6a3804addc
feat: Replace FastAStarAlgorithm with BitmapAStarAlgorithm (#2446)
## Summary

Replaces `FastAStarAlgorithm` with `BitmapAStarAlgorithm`: one cache lookup per cell expansion (8-direction mask + per-direction destination Z) instead of 8 separate `MovementImpl.CheckMovement` calls. Adds the supporting cache infrastructure to back it.

Public API unchanged — `MovementPath` / `Mobile.Move` / `CalcMoves.Find` return the same shapes; the algorithm swap is internal.

## What's in this PR

- **`BitmapAStarAlgorithm`** — A* that issues one `StepCache.TryGetMask` call per cell expansion. Inline fallthrough to the per-cell slow path for multi-Z, off-map, source-Z mismatch, and non-default walkers.
- **`StepCache`** — singleton chunk store keyed by `(mapId, chunkX, chunkY)`. Lazily built on first query, invalidated by `Sector.MultisVersion` mismatch, memory-bounded by sampled probabilistic LRU.
- **`StepProbe`** — computes static-only walkability for a single cell, mirroring `MovementImpl.Check` minus the item / mobile collision phases.
- **`StepMask` / `StepChunk`** — value / storage types for the per-cell results.
- **`CacheEvictionTimer`** — periodic cap backstop (60s interval; early-returns when not over cap).
- **`Map.Sector.MultisVersion`** promoted to `public` so the cache can detect dynamic-static invalidations cheaply.

## Eviction strategy

Sampled probabilistic LRU (Redis-style). Per eviction, sample 5 random keys from a parallel `List<long>` kept in lockstep with the chunk dictionary; evict the oldest of the sample via swap-and-pop. O(1) per eviction regardless of resident count, so sustained cap pressure has no perpetual perf hit.

## Capability handling (interim)

Non-default walkers (non-GM players, creatures with `CanSwim` / `CanFly` / `CanOpenDoors` / `CanMoveOverObstacles`) route entirely through the per-cell slow path via `BitmapAStarAlgorithm.GetSuccessorsSlowPath`. The 2-pass design (cache + capability overlay + dynamic-obstacle pass) lands in the follow-up PR.
2026-05-05 21:53:43 -07:00

120 lines
3.3 KiB
C#

using System;
using System.Diagnostics;
using Server.Engines.Pathing.Cache;
using Server.Items;
using Server.PathAlgorithms;
using Server.PathAlgorithms.BitmapAStar;
using Server.Spells;
using Server.Targeting;
namespace Server
{
public sealed class MovementPath
{
public MovementPath(Mobile m, Point3D goal)
{
var start = m.Location;
var map = m.Map;
Map = map;
Start = start;
Goal = goal;
if (map == null || map == Map.Internal)
{
return;
}
if (Utility.InRange(start, goal, 1))
{
return;
}
try
{
var alg = OverrideAlgorithm ?? BitmapAStarAlgorithm.Instance;
if (alg?.CheckCondition(m, map, start, goal) == true)
{
Directions = alg.Find(m, map, start, goal);
}
}
catch (Exception e)
{
Console.WriteLine("Warning: {0}: Pathing error from {1} to {2}", e.GetType().Name, start, goal);
}
}
public Map Map { get; }
public Point3D Start { get; }
public Point3D Goal { get; }
public Direction[] Directions { get; }
public bool Success => Directions?.Length > 0;
public static PathAlgorithm OverrideAlgorithm { get; set; }
public static void Configure()
{
CommandSystem.Register("Path", AccessLevel.GameMaster, Path_OnCommand);
CacheEvictionTimer.Configure();
}
[Usage("Path")]
[Description("Draws a path from your current location to a targeted location.")]
public static void Path_OnCommand(CommandEventArgs e)
{
e.Mobile.BeginTarget(-1, true, TargetFlags.None, Path_OnTarget);
e.Mobile.SendMessage("Target a location and a path will be drawn there.");
}
private static void Path(Mobile from, IPoint3D p, PathAlgorithm alg, string name, int zOffset)
{
OverrideAlgorithm = alg;
var watch = new Stopwatch();
watch.Start();
var path = new MovementPath(from, new Point3D(p));
watch.Stop();
if (!path.Success)
{
from.SendMessage($"{name} path failed: {watch.ElapsedMilliseconds}ms");
}
else
{
from.SendMessage($"{name} path success: {watch.ElapsedMilliseconds}ms");
var x = from.X;
var y = from.Y;
var z = from.Z;
WayPoint waypoint = null;
for (var i = 0; i < path.Directions.Length; ++i)
{
Movement.Movement.Offset(path.Directions[i], ref x, ref y);
waypoint = new WayPoint(waypoint);
waypoint.MoveToWorld(new Point3D(x, y, z + zOffset), from.Map);
}
}
}
public static void Path_OnTarget(Mobile from, object targeted)
{
if (targeted is not IPoint3D p)
{
return;
}
SpellHelper.GetSurfaceTop(ref p);
Path(from, p, BitmapAStarAlgorithm.Instance, "Bitmap", 0);
OverrideAlgorithm = null;
}
}
}