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a bit better bfs

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This commit is contained in:
Boki 2026-02-16 09:57:32 -05:00
parent 9de6293b1a
commit 2d6a6bd3a1
1 changed files with 57 additions and 37 deletions
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94
src/Poe2Trade.Navigation/WorldMap.cs
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@ -364,9 +364,10 @@ public class WorldMap : IDisposable
}
/// <summary>
/// BFS through walkable (Explored) cells to find the nearest frontier
/// (Explored cell adjacent to Unknown/Fog). Returns direction toward the
/// first step on the shortest path, respecting walls.
/// BFS through walkable (Explored) cells to find the best frontier direction.
/// Instead of stopping at the nearest frontier, runs the full BFS and counts
/// frontier cells reachable per first-step direction. Prefers directions with
/// more frontier cells (corridors) over directions with few (dead-end rooms).
/// </summary>
public (double dirX, double dirY)? FindNearestUnexplored(MapPosition pos, int searchRadius = 400)
{
@ -379,24 +380,24 @@ public class WorldMap : IDisposable
var rr = searchRadius / step;
var gridW = 2 * rr + 1;
// Visited grid + parent tracking (encode parent as single int)
var visited = new bool[gridW * gridW];
var parentX = new short[gridW * gridW];
var parentY = new short[gridW * gridW];
// Propagate first step from start during BFS (avoids per-frontier trace-back)
var firstStepX = new short[gridW * gridW];
var firstStepY = new short[gridW * gridW];
var queue = new Queue<(int gx, int gy)>(4096);
var startGx = rr;
var startGy = rr;
visited[startGy * gridW + startGx] = true;
parentX[startGy * gridW + startGx] = -1;
parentY[startGy * gridW + startGx] = -1;
queue.Enqueue((startGx, startGy));
// 8-connected neighbors
ReadOnlySpan<int> dxs = [-1, 0, 1, -1, 1, -1, 0, 1];
ReadOnlySpan<int> dys = [-1, -1, -1, 0, 0, 1, 1, 1];
int foundGx = -1, foundGy = -1;
// Count frontier cells per first-step direction
var frontierCounts = new Dictionary<int, int>();
var firstStepCoords = new Dictionary<int, (short gx, short gy)>();
while (queue.Count > 0)
{
@ -407,8 +408,9 @@ public class WorldMap : IDisposable
var wy = cy + (gy - rr) * step;
// Check if this explored cell borders Unknown/Fog (= frontier)
if (gx != startGx || gy != startGy) // skip player cell
if (gx != startGx || gy != startGy)
{
var cellIdx = gy * gridW + gx;
for (var d = 0; d < 8; d++)
{
var nx = wx + dxs[d] * step;
@ -417,9 +419,15 @@ public class WorldMap : IDisposable
var neighbor = _canvas.At<byte>(ny, nx);
if (neighbor == (byte)MapCell.Unknown || neighbor == (byte)MapCell.Fog)
{
foundGx = gx;
foundGy = gy;
goto Found;
var fsKey = firstStepY[cellIdx] * gridW + firstStepX[cellIdx];
if (frontierCounts.TryGetValue(fsKey, out var cnt))
frontierCounts[fsKey] = cnt + 1;
else
{
frontierCounts[fsKey] = 1;
firstStepCoords[fsKey] = (firstStepX[cellIdx], firstStepY[cellIdx]);
}
break; // don't double-count this cell
}
}
}
@ -439,43 +447,54 @@ public class WorldMap : IDisposable
if (nwx < 0 || nwx >= size || nwy < 0 || nwy >= size) continue;
var cell = _canvas.At<byte>(nwy, nwx);
if (cell != (byte)MapCell.Explored) continue; // only walk through explored
if (cell != (byte)MapCell.Explored) continue;
visited[idx] = true;
parentX[idx] = (short)gx;
parentY[idx] = (short)gy;
// Propagate first step: direct neighbors of start ARE the first step
if (gx == startGx && gy == startGy)
{
firstStepX[idx] = (short)ngx;
firstStepY[idx] = (short)ngy;
}
else
{
var parentIdx = gy * gridW + gx;
firstStepX[idx] = firstStepX[parentIdx];
firstStepY[idx] = firstStepY[parentIdx];
}
queue.Enqueue((ngx, ngy));
}
}
Log.Information("BFS: no reachable frontier within {Radius}px", searchRadius);
return null;
Found:
// Trace back to first step from start
var traceX = foundGx;
var traceY = foundGy;
while (true)
if (frontierCounts.Count == 0)
{
var idx = traceY * gridW + traceX;
var px = parentX[idx];
var py = parentY[idx];
if (px == startGx && py == startGy)
break; // traceX/traceY is the first step
traceX = px;
traceY = py;
Log.Information("BFS: no reachable frontier within {Radius}px", searchRadius);
return null;
}
var dirX = (double)(traceX - startGx);
var dirY = (double)(traceY - startGy);
// Pick direction with the most frontier cells (prefers corridors over dead ends)
var bestKey = -1;
var bestCount = 0;
foreach (var (key, count) in frontierCounts)
{
if (count > bestCount)
{
bestCount = count;
bestKey = key;
}
}
var (bestGx, bestGy) = firstStepCoords[bestKey];
var dirX = (double)(bestGx - startGx);
var dirY = (double)(bestGy - startGy);
var len = Math.Sqrt(dirX * dirX + dirY * dirY);
if (len < 0.001) return (1, 0); // shouldn't happen
if (len < 0.001) return (1, 0);
dirX /= len;
dirY /= len;
var dist = Math.Sqrt((foundGx - startGx) * (foundGx - startGx) + (foundGy - startGy) * (foundGy - startGy)) * step;
Log.Debug("BFS: frontier at {Dist:F0}px, first step dir=({Dx:F2},{Dy:F2})", dist, dirX, dirY);
Log.Debug("BFS: {DirCount} directions, best={Best} frontier cells, dir=({Dx:F2},{Dy:F2})",
frontierCounts.Count, bestCount, dirX, dirY);
return (dirX, dirY);
}
@ -504,7 +523,8 @@ public class WorldMap : IDisposable
colored.Set(r, c, new Vec3b(104, 64, 31));
else if (v == (byte)MapCell.Wall)
colored.Set(r, c, new Vec3b(26, 45, 61));
// Fog not rendered — too noisy from spell effects bleeding through overlay
else if (v == (byte)MapCell.Fog)
colored.Set(r, c, new Vec3b(55, 40, 28));
}
var px = cx - x0;