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Collision walls in Godot

I'm creating a game using Godot Engine and I can't figure out how to create a wall to prevent a player from walking out of the screen.

The player is able to walk out of the screen window. How do I prevent it from happening?

I tried to use the CollisionShape2D node but I don't think I know how to use it properly in a way that it works like I want it to.

Solution

  • Note: What I explain here also holds for the 3D counterpart of these nodes.

    CollisionShape2D and CollisionPolygon2D do nothing on their own. Their purpose is to provide a shape for a parent CollisionObject2D.

    There are two kinds of CollisionObject2Ds: Area2D and PhysicsBody2D.

    The Area2D will detect other bodies or areas, but won't stop them from moving, which is not what you want.

    There are three kinds of PhysicsBody2D:

    • CharacterBody2D: which is intended to be moved via script, usually to make character controllers.
    • RigidBody2D: which is moved by the physics engine, usually to make bodies that can be pushed around by other bodies.
    • StaticBody2D: which either do not move (or have a predefined motion). This is the one you want.

    Thus, you would setup a StaticBody2D with a child CollisionShape2D or CollisionPolygon2D.

    Now, I'm also going to point out that physic bodies interact with physic bodies. If you, for example, have created your character as an Sprite2D, since the Sprite2D only cares about graphics and does not have collisions it will not be stopped by the StaticBody2D.

    So you usually make your character as a body that can collide (usually a CharacterBody2D, sometimes a RigidBody2D), and it would, of course, have a child CollisionShape2D or CollisionPolygon2D, and also as child it can have your Sprite2D or whatever else you need.

    By making the Sprite2D and other Node2Ds children of the physics body, they will move with it.

    If you haven't decided between CharacterBody2D and RigidBody2D, I go into more length on which kind of node to use for what elsewhere. A very good abstract is the following: If something else can push it, use a RigidBody2D. following the link you get the nuance and what to use for specific cases.

    For the CollisionShape2D to set its shape property to a Shape2D.

    About making the boundary for the game, the recommendation is to use WorldBoundaryShape2D for each edge. However, thick enough RectangleShape2D would also work.

    Alternatively, although not recommended, you could use a CollisionPolygon2D covering the play area, and set its build_mode to BUILD_SEGMENTS, which results in a hollow polygon, so other bodies can be inside of it.