RigidBody3D in Godot – Complete Guide

Welcome to our comprehensive tutorial on using the RigidBody3D class in Godot 4! This powerful class opens up a universe of possibilities when it comes to simulating physics in a 3D environment. Understanding RigidBody3D is crucial for creating dynamic, interactive, and believable worlds in your games. Whether you’re building a complex machine, simulating a natural environment, or just making a stack of boxes topple over in a satisfying way, RigidBody3D is your go-to tool.

What is RigidBody3D?

RigidBody3D is a type of PhysicsBody3D that represents objects which are influenced by physics simulations within Godot’s engine. Unlike static bodies that are immovable or kinematic bodies that are controlled programmatically, RigidBody3D objects are swayed by forces, collisions, and constraints in the game world. They act under the laws of physics, creating a base for realistic simulations.

Understanding RigidBody3D’s Role

RigidBody3D is vital for game designers looking to implement physics-based objects. It finds its use anywhere from the debris of an exploded spaceship to the naturally swaying trees in a forest. With this class, objects take on behaviors like bouncing, rolling, or being pushed by other entities. By tweaking its properties, game creators can achieve various effects and interactions that make the game environment more engaging and responsive.

Why Should You Learn RigidBody3D?

Learning RigidBody3D is a significant step towards mastering game development in Godot 4. It provides the following benefits:

  • Realistic Physics Simulation: Harness the power of Godot’s built-in physics engine to create objects that interact with the game world in realistic ways.
  • Interactive Gameplay: Enhance player experience by implementing objects that can be affected by players’ actions or other in-game forces.
  • Creative Control: Take creative control over your game’s mechanics by manipulating physics properties to suit gameplay requirements.

Whether you’re an aspiring game developer or an experienced programmer, getting comfortable with RigidBody3D will elevate your game creation skills and help bring your imaginative game ideas to life. So, buckle up, and let’s dive into the world of 3D physics with RigidBody3D in Godot!

CTA Small Image
FREE COURSES AT ZENVA
LEARN GAME DEVELOPMENT, PYTHON AND MORE
ACCESS FOR FREE
AVAILABLE FOR A LIMITED TIME ONLY

Basic RigidBody3D Setup

Let’s start by adding a RigidBody3D node to our project and configuring its basic properties. To create a new RigidBody3D, you simply select ‘3D Scene’ as a root node and then add a ‘RigidBody3D’ as its child:

var body = RigidBody3D.new()
add_child(body)

Now attach a shape to your body – this is necessary for collision detection. A common practice is to combine it with a ‘CollisionShape3D’ node containing a ‘BoxShape3D’, which acts as the body’s shape in the physical world:

var shape = CollisionShape3D.new()
var box_shape = BoxShape3D.new()
shape.shape = box_shape
body.add_child(shape)

Set the body’s mass properties:

body.mass = 1.0  # Set the mass to 1.0 kg

Applying Forces and Impulses

To move our RigidBody3D, let’s apply some force. Here, we’re adding a continuous force, which will keep acting on the body:

body.apply_central_force(Vector3(0, -9.8, 0))  # Apply gravity-like force

An impulse is a force applied instantaneously. This is how you’d apply an impulse to the RigidBody3D to make it jump:

body.apply_impulse(Vector3.ZERO, Vector3(0, 10, 0))  # Apply an upward impulse

Manipulating RigidBody3D Properties

You can alter the physics properties of RigidBody3D at runtime or within the editor. Here’s how to change the damping properties:

body.linear_damp = 0.5  # Change the linear damping
body.angular_damp = 0.5  # Change the angular damping

The RigidBody3D’s mode can also be changed, switching between Rigid, Static, Character, and Kinematic modes:

body.mode = RigidBody3D.MODE_KINEMATIC  # Change the mode to kinematic

Responding to Collisions

You’ll often need your RigidBody3D to respond to collisions. Here’s how you can connect a signal to listen for collisions:

body.connect("body_entered", self, "_on_body_entered")

func _on_body_entered(body):
    print("Collided with ", body.name)

Additionally, you can react to the contact information, which provides details of the collision:

func _on_body_entered(body):
    var contacts = body.get_colliding_bodies()
    if contacts:
        for contact in contacts:
            print("Contact point: ", contact.collider_velocity)

These examples cover the basics of using RigidBody3D in Godot 4. By setting up the node, applying forces and impulses, adjusting properties, and responding to collisions, you create the foundation for intricate physics simulations in your 3D games. Stay tuned for the next part, where we’ll delve into more advanced use cases and examples!

In the previous section, we covered the foundational elements of working with the RigidBody3D class in Godot 4. To expand our toolkit further, let’s explore advanced techniques and code examples that will add sophistication to your 3D physics simulations.

Changing the collision layer and mask is critical for controlling which bodies can interact with each other. Here’s how you can make a RigidBody3D only collide with certain layers:

body.collision_layer = 1 
body.collision_mask = 2

This means your RigidBody3D is on layer 1 and will only register collisions with bodies in layer 2, allowing you to create complex interaction rules.

It’s also important to manage the state of the RigidBody3D for optimization purposes. You can deactivate a body that is at rest to save on computational resources:

body.can_sleep = true  # Allow the RigidBody3D to sleep

But, if you need to wake it up again manually, perhaps because of an event or action, use:

body.wake_up()

To lock the RigidBody3D’s rotation or position, which is handy for creating sliding objects or characters that shouldn’t tumble over, you can configure the body’s axes settings:

body.angular_lock_enabled = true
body.angular_lock_axis = Vector3(1, 1, 0)  # Lock rotation around the X and Y axes
body.linear_lock_enabled = true
body.linear_lock_axis = Vector3(0, 1, 0)  # Lock movement along the Y axis

Sometimes you may want to directly set the velocity of a RigidBody3D. Here’s how to give it an initial push along the X axis:

body.linear_velocity = Vector3(10, 0, 0)

For a rotating motion:

body.angular_velocity = Vector3(0, 5, 0)  # Spin around the Y axis

If you’re aiming for an interactive game environment, detecting when a RigidBody3D has come to rest can trigger events or actions:

func _integrate_forces(state):
    if state.linear_velocity.length() < 0.01 and state.angular_velocity.length() < 0.01:
        print("Body has come to rest")

Let’s explore how to combine RigidBody3D nodes with joints for more complex physical interactions. We will use a HingeJoint3D to create a swinging door:

var hinge_joint = HingeJoint3D.new()
var door_body = RigidBody3D.new()
add_child(hinge_joint)
hinge_joint.set_node_a(body.get_path())  # Connect the joint to the main body
hinge_joint.set_node_b(door_body.get_path())  # Connect the joint to the door body

These code examples show the versatility of the RigidBody3D class in Godot 4. By mastering these techniques, you can create a dynamic and interactive 3D game environment. Combine these commands with your creative ideas to create complex physics interactions that can make your game stand out.

Delving deeper into our exploration of Godot’s RigidBody3D, we venture into the realm of advanced behaviors and effects to truly bring our game environments to life. Let’s put the pedal to the metal and kick things up a notch with more interactive and nuanced physics examples.

Detecting and responding to collisions is a central aspect of physics simulations. Beyond the simple collision detection example before, here’s how you can apply a reaction force upon collision:

func _on_body_entered(body):
    var reaction_force = Vector3(10, 0, 0)  # Replace with desired force vector
    body.apply_central_impulse(reaction_force)

This snippet applies an instantaneous force to the other body upon collision, which may simulate a repulsive effect or an explosion.

Interpolated transforms can smooth out the motion of rigid bodies, which is particularly useful for networked games or when aiming for cinematic quality:

func _physics_process(delta):
    var target_transform = Transform()
    # Calculate your target transform based on game logic
    body.global_transform = body.global_transform.interpolate_with(target_transform, delta * 10.0)

This code gradually moves a RigidBody3D towards a target transform, providing a smooth transition between two states.

Modifying the center of mass can have significant effects on the stability and movement of a RigidBody3D. Adjusting the center of mass property within Godot can simulate carrying heavy objects or change the body’s rotation behavior:

body.center_of_mass = Vector3(0, -1, 0)  # Shift the center of mass downwards

For game objects that should temporarily not react to physics, such as during a cutscene, you can disable their simulation:

body.mode = RigidBody3D.MODE_STATIC  # Pause physics simulation
# -- Your cutscene logic goes here --
body.mode = RigidBody3D.MODE_RIGID  # Resume physics simulation

This toggles the RigidBody3D between static and rigid modes, effectively pausing and resuming its physics interactions.

To add a sense of weight and inertia to your objects, playing with the mass and inertia properties can make them feel more heavy and ponderous or light and nimble:

body.mass = 10  # Increase the body's mass
body.inertia = Vector3(1, 1, 1)  # Adjust the body's inertia tensor

For scenarios where a RigidBody3D must follow a path or be guided by a scripted motion, the use of forces might not suffice. In such cases, combining forces with calculated velocity vectors could steer the body along a predetermined route:

func _integrate_forces(state):
    var desired_velocity = Vector3(5, 0, 0)  # The velocity you want the body to reach
    var velocity_diff = desired_velocity - state.linear_velocity
    var force_to_apply = velocity_diff * body.mass / state.step
    body.apply_central_force(force_to_apply)

Lastly, for subtle environmental effects like wind or water currents, attaching area nodes with their own physics properties to affect RigidBody3D nodes passing through can create immersive environmental interactions:

var area = Area3D.new()
var force_vector = Vector3(2, 0, 0)  # The direction and strength of the wind
area.add_constant_force(force_vector)
add_child(area)

Through these varied examples, we’ve seen how Godot’s RigidBody3D class can extend the physical realism in our games. This reality-mimicking layer not only enhances the visual fidelity but also infuses your games with a depth that resonates with players, injecting your virtual worlds with a tangible, believable presence. Combine, tweak, and build upon these examples to fully unleash the potential of physics in your Godot 4 projects.

Continuing Your Game Development Journey

As you’ve seen through this tutorial, unlocking the capabilities of the RigidBody3D class in Godot 4 is just the beginning of an exciting journey in game development. There’s always more to learn, more to create, and more to discover. If you’re passionate about creating engaging and interactive games, we encourage you to continue expanding your skills and knowledge.

For those keen on delving deeper into the world of Godot game development, we invite you to explore our Godot Game Development Mini-Degree. This comprehensive collection of curated courses will guide you through the process of building cross-platform games using Godot’s robust features.

Whether you’re just starting out or honing your developing skills, our broad selection of Godot courses caters to all levels. At Zenva, we’re committed to helping you grow at every stage of your development journey. Join our vibrant community of over 1 million learners and take the next step towards achieving your game development aspirations.

Conclusion

In mastering the RigidBody3D class in Godot 4, you’ve unlocked a new dimension of dynamic gameplay for your projects. The power to simulate complex physical interactions will not only enhance the realism within your games but also allow for innovative gameplay mechanics that can truly captivate your audience. We hope that the skills and examples presented in this tutorial inspire you to experiment and innovate as you create your unique game worlds.

Our journey doesn’t end here. There’s always room for growth and perfection in the art of game development. Embrace this opportunity to further your expertise with Zenva’s Godot Game Development Mini-Degree. Together, we can turn your vision into an extraordinary gaming experience that stands out in an ever-evolving digital world. Let’s keep learning, creating, and pushing the boundaries of what’s possible in game development!

FREE COURSES
Python Blog Image

FINAL DAYS: Unlock coding courses in Unity, Godot, Unreal, Python and more.