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Pathfinding

MD Engine includes an optional pathfinding module that automatically finds routes between two points on a scene's collision map. It supports multiple search algorithms with different movement styles and tradeoffs.

The module only gets compiled into your ROM if your project uses any pathfinding events.

Algorithms​

You can choose the pathfinding algorithm in the Settings panel under Pathfinding.

The default algorithm. Searches in 8 directions (including diagonals) and finds paths very quickly. Paths are usually good but may not always be the absolute shortest route, especially around complex obstacles. Best suited for most games.

A* (A-Star)​

Searches in 8 directions and always finds the optimal path. Slightly slower than Best-First Search but guarantees the shortest route. Best suited for games where path quality matters more than speed.

Pathfinding example showing an actor following a calculated path

How It Works​

  1. Find Path computes a route from a start position to a goal position, avoiding collision tiles.
  2. The result is stored in a path slot (referenced by a variable). The path is a sequence of direction steps.
  3. Follow Path makes an actor walk the path step by step at a given speed.
  4. When the actor finishes walking, the path slot can be reused.

Path Slots​

Paths are stored in a fixed-size pool. The number of simultaneous path slots can be configured in Settings (default: 4, range: 2-8). Each slot holds up to 64 direction steps.

A path slot is allocated when you use Find Path and must be freed when you no longer need it. If all slots are in use, Find Path will fail.

warning

Always free path slots when you're done with them. If you forget, the pool will fill up and no new paths can be computed.

Scripting Events​

For a full reference of all pathfinding events with field descriptions and previews, see the Pathfinding Event Glossary.

Settings​

The pathfinding settings are found in the Pathfinding section of the Settings panel.

  • Max Paths - The maximum number of simultaneous path slots (default: 4, range: 2-8).
  • Budget - Controls how much work the pathfinder does per frame when using non-blocking mode (default: 64). Higher values find paths faster but may slow down your game. Set to 0 for unlimited.
  • Algorithm - Choose between Best-First Search (fast) and A* (optimal).
  • Queue Size - Controls how large an area the pathfinder can search. The default (Small) works for most games. Increase if pathfinding fails on very large open maps.

Tips​

  • Use the smallest actor footprint that makes sense for your game. Smaller actors are significantly faster to pathfind.
  • For blocking searches on small-to-medium maps, the path is typically found instantly with no perceptible delay.
  • For large maps or real-time searches, use non-blocking mode (uncheck Block Until Found) and adjust the Budget setting to balance path-finding speed against frame time.
  • Best-First Search is the fastest algorithm overall but may occasionally take a longer route around complex obstacles. If path quality matters, use A*.
  • Make sure your collision map accurately represents walkable areas.

See Also​

  • Collisions - Collision system and collision tile settings
  • Behaviours - Movement behaviours for actors