SetNet.PathFinding 1.3.2

SetNet.PathFinding

Pathfinding + path-following for SetNet, over SetNet.GeoData.

Find a route, then walk an entity along it — server-side and engine-agnostic. One interface, IPathfinder, with the right algorithm picked from the geometry kind:

• grid → A* (8-connected, octile, no corner-cutting) + straight-line smoothing
• multi-storey grid → A* over per-cell height layers (climbs stairs / crosses bridges between floors) + smoothing
• nav-mesh → A* over triangles + portal path + straight-line smoothing

IGeoData geo = GeoDataFile.LoadFromFile("world.geo");
IPathfinder finder = Pathfinding.For(geo);            // grid or nav-mesh — automatic

Path path = finder.FindPath(mobPos, playerPos);
if (!path.IsEmpty)
{
    var follower = new PathFollower(path);
    // each server tick:
    mobPos = follower.Step(mobPos, speed * dtSeconds);   // moves toward the next waypoint
    if (follower.Arrived) { /* reached the goal */ }
}

Built for scale (path everyone, every tick)

In an MMO every character and mob may re-path several times a second, so the hot path is allocation-free after warm-up. A pathfinder instance is meant to be built once and reused (that's exactly how SetNet.Mobs holds it):

• Per-query working memory (g/came/closed sets, the open heap) is pooled and reused across calls — nothing is allocated per FindPath once the pool is warm.
• Visited nodes are generation-stamped instead of cleared, so a query costs O(nodes actually expanded), not O(map size) — a short path on a huge map stays cheap.
• The pool is thread-safe, so one pathfinder can serve many agents from parallel AI ticks.
• MaxExpansions (on GridPathfinder / LayeredGridPathfinder) caps the worst case: an unreachable goal returns Path.Empty instead of scanning the whole reachable area.

var finder = Pathfinding.For(geo);        // build ONCE, keep it
// ...thousands of times, from any thread:
var path = finder.FindPath(a, b);         // no per-call array allocation

The World example (dotnet run --project examples/World -- bench) reports throughput on a reused instance.

Notes

• Server-side, no wire protocol. Movement is server-authoritative; clients see replicated positions.
• PathFollower is what SetNet.Mobs uses to turn a MoveTo intent into authoritative motion — but Mobs treats the pathfinder as an optional seam (straight-line fallback when no IGeoData is provided).
• Nav-mesh routing uses a portal-midpoint path with line-of-walk smoothing (a robust stand-in for a full funnel).

License

MIT