Physics on Godot 4 レシピ

RigidBody2D: Look at Target

Mon, 01 Jan 0001 00:00:00 +0000

Problem

You want a rigid body to rotate smoothly to look at a target.

Solution

Using RigidBody2D can be tricky. Because it’s controlled by Godot’s physics engine, you need to apply forces rather than moving it directly. Before doing anything with rigid bodies, I highly recommend looking at the RigidBody2D API doc.

To rotate a body, we need to apply a rotational force - a torque. Once the body is rotating, we want the torque to get smaller as we get closer to the final rotation.

CharacterBody3D: Stopping on Slopes

Mon, 01 Jan 0001 00:00:00 +0000

Tip

This article is being updated from Godot 3 to Godot 4.

Problem

Your CharacterBody3D slides down slopes.

Solution

We’ve started with a no-frills CharacterBody3D, using move_and_slide(), using the script below:

extends CharacterBody3D

@export var gravity = -10.0
@export var speed = 5.0
@export var rot_speed = 4.0
@export var jump_speed = 5.0

var velocity = Vector3.ZERO
var jumping = false

func get_input(delta):
 var input = Vector3.ZERO
 if Input.is_action_pressed("forward"):
 input += -transform.basis.z * speed
 if Input.is_action_pressed("back"):
 input += transform.basis.z * speed
 if Input.is_action_pressed("right"):
 rotate_y(-rot_speed * delta)
 if Input.is_action_pressed("left"):
 rotate_y(rot_speed * delta)
 velocity.x = input.x
 velocity.z = input.z

func _physics_process(delta):
 get_input(delta)
 velocity.y += gravity * delta

 move_and_slide()

 if jumping and is_on_floor():
 jumping = false

 if Input.is_action_just_pressed("jump"):
 if is_on_floor():
 jumping = true
 velocity.y = jump_speed

We see the problem if we stop moving on a slope:

Collision Layers and Masks

Mon, 01 Jan 0001 00:00:00 +0000

Introduction

Collision layers and masks are essential for controlling which objects interact with each other in Godot 4.

The System

Collision Layer: Which layer(s) the object lives on.
Collision Mask: Which layer(s) the object scans for collisions.

Example Configuration

Node	Layer	Mask	Interaction
Player	1	2, 3	Scans for Enemies and Coins
Enemy	2	1	Scans for the Player
Coin	3	(None)	Doesn’t need to scan anything

Setting Names

In Godot 4, you can name your layers in Project Settings > Layer Names > 2D Physics. This makes it much easier to manage in the Inspector.

Kinematic Friction

Mon, 01 Jan 0001 00:00:00 +0000

Tip

This article is being updated from Godot 3 to Godot 4.

Problem

You want to add friction and acceleration to your kinematic character, giving it a smoother feel.

Solution

For most games, we’re not necessarily interested in a perfect physics simulation. We want action, responsiveness, and arcade feel. This is why you choose a kinematic body over a rigid one: so that you can control its behavior directly. However, some amount of physics is good - it means an object doesn’t instantly change direction or come to a stop.

RigidBody2D: Move to Target

Mon, 01 Jan 0001 00:00:00 +0000

Problem

You want a rigid body to move to a target position.

Solution

To move a body, we need to apply a push in a given direction - a force. Once the body is moving, we want the force to get smaller as we get closer to the final position.

RigidBody2D: Drag and Drop

Mon, 01 Jan 0001 00:00:00 +0000

Problem

You want to pick up and move rigid bodies with the mouse.

Solution

Working with rigid bodies can be tricky. Godot’s physics engine controls their movements, and interfering with that can often lead to unexpected results. The key is to make use of the body’s mode property. This applies equally well in 2D or 3D.

Body setup

We’ll start with our rigid body object, adding a Sprite2D and CollisionShape2D. You can also add a PhysicsMaterial if you want to set Bounce and Friction properties.

Character to Rigid Body Interaction

Mon, 01 Jan 0001 00:00:00 +0000

Problem

You want your character body to interact with rigid bodies.

Solution

Note

This recipe applies equally well in both 2D and 3D nodes.

By default, a CharacterBody2D moved with move_and_slide() or move_and_collide() will not push any RigidBody2D it collides with. The rigid body doesn’t react at all, and behaves just like a StaticBody2D.

In some cases, this might be all you need. However, if you want to be able to push the bodies, you’ll need to make some changes.

Using 2D Joints

Mon, 01 Jan 0001 00:00:00 +0000

Tip

This article is being updated from Godot 3 to Godot 4.

Problem

You’d like to understand Godot’s Joint2D nodes.

Solution

Joint are used to constrain the movement of attached physics objects. For any joint node, you need to attach two bodies, which must extend from PhysicsObject2D.

Properties

These properties are common to all joint nodes:

Node A and Node B: The assigned physics bodies.
Bias: The rate at which the joint pulls the two bodies back together if they move apart. Defaults to 0.
Disable Collisions: Allows the connected bodies to ignore collisions between them. Defaults to true.

There are three types of Joint2D. In all of the following examples, there is one RigidBody2D connected via a joint to a StaticBody2D. “Visible Collision Shapes” is enabled in the screen images below so you can see a representation of the joint.

Conveyor Belt

Mon, 01 Jan 0001 00:00:00 +0000

Tip

This article is being updated from Godot 3 to Godot 4.

Problem

You want to make a conveyor belt object that will move bodies (kinematic or rigid).

Solution

You can make a conveyor belt object using nothing but a StaticBody2D by using its constant_linear_velocity property.

Note

See below for how to address this in 3D.

Here’s an example, using a StaticBody2D and a RigidBody2D. No code was added. The static body’s Constant Linear Velocity is set to (200, 0).

Asteroids-style Physics (using RigidBody2D)

Mon, 01 Jan 0001 00:00:00 +0000

Problem

You want to use a RigidBody2D to create a semi-realistic spaceship, a la Asteroids.

Solution

For this example, we’ll use the following node setup: