What is it?

Collision events are often used in game development to trigger events or reactions based on collisions. For example, a collision between a player character and an enemy could trigger damage to the player, while a collision between a player and a collectible item could trigger a pickup event. The collision event system uses the Observable and Observer system, which is also used in other parts of Babylon.js.

How to use

To use collision callbacks, first, the body needs to have the callback enabled. This can be achieved with setCollisionCallbackEnabled. Then, we need to obtain the collision Observable by calling getCollisionObservable on the body. You can have either a body-specific callback or a world-wide callback. The second option requires filtering for the correct body to process, but it is more performant.

// player is a PhysicsBody
// You have two options:
// Body-specific callback
const observable = player.getCollisionObservable();
const observer = observable.add((collisionEvent) => {
// Process collisions for the player
// OR
// world callback
const observable = plugin.onCollisionObservable;
const observer = observable.add((collisionEvent) => {
// Check if the player is involved in the collision
if (collisionEvent.collider === player || collisionEvent.collidedAgainst === player) {
// Process collisions for the player
// ...
Collision observers

Further reading