Use Case 2 TileMaps and Triggers

Problem Statement

We have a player, and we want it to not pass through the outer tiles of the tilemap. We will use the solid property on the tiles to add a collider. Also, we want the player to step on a trigger to show a prize.

tip

TileMaps use something called a "composite collider" to represent their collision geometry. A composite collider is a way of treating multiple pieces of geometry as one collider.

Composite Collision Resolution Strategy

1. 'together' - Treat all geometry as part of the same body, meaning only 1 contact is possible for the composite, and only 1 event is generated.
2. 'separate' - Treat geometry as if it were part of separate bodies, a contact is possible for every piece of geometry, an event is generated for every contact.

Set the default for all composites as engine config

typescript
const game = new ex.Engine({
  ...
  physics: {
    colliders: {
      compositeStrategy: 'separate'
    }
  }
});

typescript
const game = new ex.Engine({
  ...
  physics: {
    colliders: {
      compositeStrategy: 'separate'
    }
  }
});

Or per composite

typescript
const tm = new ex.TileMap({...});
// TileMaps only have CompositeColliders
const comp = tm.collider.get() as ex.CompositeCollider;
comp.compositeStrategy = 'separate';

typescript
const tm = new ex.TileMap({...});
// TileMaps only have CompositeColliders
const comp = tm.collider.get() as ex.CompositeCollider;
comp.compositeStrategy = 'separate';

Rule of Thumb

• If your composite is connected and has no large gaps, use 'together'
• If your composite is a level like a platformer with large gaps, use 'separate'

Demonstrates:

• Tilemap colliders
• Triggers
• Collectibles
• Spawning

Using the demo:

• WASD to move the orange player
• The gray tiles are solid
• The black circle is a button to press
• Pressing the button drops a coin to pick up
• Rinse and repeat

Takeaways from this use case

Tilemaps can set the solid property on tile for any of the tiles

You can build whatever wall layout and each tile will have a collider on it.

Triggers can be used instead of Actors

Triggers are a special type of entity that can be less expensive than using an actor for just triggering a collision event.