0xheycat Isometric Pathfinding
Overview
Pathfinding runs on grid coordinates, not screen pixels. This skill implements A* over the walkable layer with proper diagonal handling so units take natural paths and never cut through blocked corners.
When to Use
- Units or NPCs need to move to a target around obstacles.
- Characters walk through walls or take ugly paths.
- You have a walkable layer and need movement on it.
Process
- Run A* on grid coords using the tilemap walkable layer.
- Define neighbors: 4-way or 8-way; for 8-way, forbid cutting blocked corners.
- Use an admissible heuristic (octile distance for 8-way).
- Return a path of grid tiles, then convert to screen with
isometric-grid-math. - Smooth the path (string-pulling) to avoid zig-zag.
- Recompute or repath when the map or target changes.
- Cap search cost (node budget) for large maps.
heuristic (octile): dx=|x1-x2|, dy=|y1-y2|; h = (dx+dy) + (1.414-2)*min(dx,dy)
Rationalizations (Stop Lying to Yourself)
| Excuse | Reality |
|---|---|
| "Straight-line movement is fine" | Units will walk into walls. Use A* on the walkable layer. |
| "Corner cutting looks fine" | Units clip through diagonal walls. Forbid blocked-corner cuts. |
Red Flags - STOP if you catch yourself:
- Pathfinding on screen coords instead of grid coords.
- Allowing diagonal moves through blocked corners.
- No node budget so large maps freeze.
Verification
You are NOT done until every box is checked:
- A* finds paths around obstacles on the walkable layer.
- Diagonal moves never cut blocked corners.
- Path converts correctly back to screen positions.