Collision

Player Collision Handling

Player Creation

The Player's collision is handled entirely by the Box2D Physics engine. When a player is being generated via 'PlayerFactory', 3 key components are added to the entity. These are PhysicsComponent, ColliderComponent and HitboxComponent, which are then used by the PhysicsEngine when monitoring and calculating collision physics. For two entites to collide, and not phase through each other, the are require to have all three components.

How it works

Collision Physics: ColliderComponent attaches a physics based collider to an entity, which allows it to collide with other physics objects (any object that has the PhysicsComponent attached to it). The default shape of this collider is a rectangle, with the player at the centre. It is possible to define more complex shapes, should one be required. Several attributes, such as object density, friction and 'bounciness' are defined and store within this method.

Collision Detection: HitboxComponent, when assigned to an entity, mirrors the shape of the ColliderComponent and allows for the detection of collisions without direct interaction. Upon this component being added to an entity, HitboxComponent is also supplied a Physics Layer to place said entity upon. In the case of the Player and other NPC's, this is the PLAYER layer.

Physics Engine: During every step of the physics simulation, the PhysicsEngine uses the raycast() method to search for collisions. A ray is created at the Player's position, which ends at the 'destination' of the player's projected movement. It then checks along the length of the ray for any colliders in the specified "Physics Layer" (PLAYER in this case), returns to the engine if a hit was detected or not. Upon hit detection, the Player's movement is restricted accoridngly.

Note that HitboxComponent is an extension of ColliderComponent that has setSensor set to true, disabling the collison. The two are presumably kept separate to avoid any errors resulting from the hitbox being the collision box.