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Revert "perf: weight-aware A* heuristic + tamed road repulsion (route-preserving speed fix)"

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This reverts commit 1f7613439a.
This commit is contained in:
Stewart Howe 2026-08-05 22:26:36 -04:00
parent 783ee8b016
commit bb0b4fe4f2
1 changed files with 3 additions and 59 deletions
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62
Tools/Scripts/MapGenerator.cs
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@ -625,9 +625,7 @@ public partial class MapGenerator : TextureRect
GD.Print($"[A*] Starting Logistics Pathfinding for {MapSize}x{MapSize} world...");
_highwayPaths.Clear(); _branchPaths.Clear(); _ruggedPaths.Clear(); _trailPaths.Clear();
// RoadPathGrid is a stock AStarGrid2D with a scaled-up distance estimate, so the
// search stops flood-filling the island for every road. See the class for why.
AStarGrid2D astar = new RoadPathGrid();
AStarGrid2D astar = new AStarGrid2D();
astar.Region = new Rect2I(0, 0, MapSize, MapSize);
astar.CellSize = new Vector2I(1, 1);
astar.DiagonalMode = AStarGrid2D.DiagonalModeEnum.OnlyIfNoObstacles;
@ -838,23 +836,6 @@ public partial class MapGenerator : TextureRect
}
}
/// <summary>
/// How much extra a step costs near an already-drawn road. This is what stops new
/// roads from lying on top of old ones — it is SEPARATION, not terrain avoidance,
/// so it is unrelated to the mountain/beach/wasteland weights.
///
/// It used to be 10,000, which was far past "discourage" — a normal step costs 1,
/// so it made the ground near a road effectively infinite. That wrecked the search:
/// every later road had to weigh routes costing tens of thousands, which is exactly
/// the situation A* handles by giving up on being clever and searching everything.
/// Worse, it compounded — each road drawn made the next one slower.
///
/// 250 still means "strongly prefer not to run alongside an existing road" (250x a
/// normal step) without dwarfing the search. Raise it if parallel roads crowd
/// together; lower it if roads take silly detours to avoid each other.
/// </summary>
private const float ROAD_REPULSION_PENALTY = 250f;
private void PenalizePath(AStarGrid2D astar, Vector2[] path, int radius)
{
int step = Mathf.Max(1, radius / 2);
@ -866,7 +847,8 @@ public partial class MapGenerator : TextureRect
int ny = Mathf.Clamp((int)p.Y + dy, 0, MapSize - 1);
var cell = new Vector2I(nx, ny);
if (!astar.IsPointSolid(cell)) {
astar.SetPointWeightScale(cell, astar.GetPointWeightScale(cell) + ROAD_REPULSION_PENALTY);
// The true Iron Curtain
astar.SetPointWeightScale(cell, astar.GetPointWeightScale(cell) + 10000f);
}
}
}
@ -968,44 +950,6 @@ public partial class MapGenerator : TextureRect
}
// Place this at the very bottom of the file!
/// <summary>
/// The road pathfinder's grid, with one change from stock: a scaled-up estimate.
///
/// WHY THIS EXISTS. A* explores outward from the start until the cheapest route it
/// has found is provably the best. It decides how far to keep looking by comparing
/// what a route has cost so far against an ESTIMATE of what remains. Godot's stock
/// estimate is plain straight-line distance — it assumes every step costs 1.
///
/// Our steps don't cost 1. A step through mountains costs up to 401, and a step near
/// an existing road used to cost 10,001. So the estimate was wildly optimistic about
/// the remaining journey, and A* responded the only way it can: by refusing to rule
/// anything out and searching almost the whole island for every single road.
///
/// Multiplying the estimate makes the search commit to a direction sooner. It's a
/// well-known trade ("weighted A*"): paths are allowed to be up to HEURISTIC_WEIGHT
/// times more expensive than the theoretical best, in exchange for exploring far less.
/// We want believable roads, not provably-optimal ones, so that's a good trade.
///
/// It does NOT make roads climb mountains. Crossing a ridge costs hundreds of times
/// more than walking around it — a 3x bias nowhere near pays for that.
/// </summary>
public partial class RoadPathGrid : AStarGrid2D
{
/// <summary>
/// How strongly the search commits toward the goal.
/// 1.0 = stock behaviour: guaranteed-shortest, explores enormously.
/// 3.0 = default: still routes sensibly around terrain, explores far less.
/// higher = faster still, but paths get progressively less considered.
/// Raise it if generation is still slow; lower it if roads start looking careless.
/// </summary>
public const float HEURISTIC_WEIGHT = 3.0f;
public override float _EstimateCost(Vector2I fromId, Vector2I toId)
{
return fromId.DistanceTo(toId) * HEURISTIC_WEIGHT;
}
}
public partial class MapDrawProxy : Control
{
public MapGenerator Source;