PhysicsServer3DExtension in Godot – Complete Guide

Welcome to our exploration of the PhysicsServer3DExtension class in Godot 4. If you’ve ever wanted to dive deeper into custom physics and really take control of how objects interact in your games, you’re in the right place. This class serves as a gateway to creating custom implementations of Godot’s physics server, allowing for unique game mechanics and fine-tuned physical simulations. By the end of this tutorial, you’ll have a thorough understanding of the capabilities the PhysicsServer3DExtension provides and how to leverage them in your game development projects. So, let’s get ready to add an extra dimension of realism to your Godot creations!

What is PhysicsServer3DExtension?

Inherits: PhysicsServer3D < Object

At its core, the PhysicsServer3DExtension class is a specialized component of the Godot Engine designed for extending the built-in PhysicsServer3D. This class offers a set of virtual methods that can be overridden to allow for customized physics behaviors.

What is it for?

Imagine being able to fine-tune the physics of your game world, crafting specific interactions and responses that standard physics engines might not default to. The PhysicsServer3DExtension is built for this very purpose—to offer game developers the ability to implement their own physics logic, integrate third-party physics engines, or just experiment with physics behaviors that might not be possible otherwise.

Why Should I Learn It?

Learning how to use the PhysicsServer3DExtension can open up a new realm of possibilities for your game development:

– Create bespoke physics interactions that help your game stand out.
– Tackle complex simulations that demand a unique approach to physics beyond the defaults.
– Customize the engine’s physics to better fit the thematic and gameplay needs of your projects.

Understanding this class lays the foundation for more intricate physics-related work, empowering both new and experienced developers to push the boundaries of what’s possible in Godot.

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Creating A Custom Physics Extension

Let’s start by setting up a basic class that inherits from PhysicsServer3DExtension. We’ll begin with an empty shell to which we can add more functionality as we progress.

class MyPhysicsServerExtension extends PhysicsServer3DExtension:
    # Additional properties and methods will be added here

Next, we’ll dive into a crucial part of creating a custom physics extension: overriding the necessary virtual methods. These methods are where you’ll define how your custom physics server will handle various tasks.

class MyPhysicsServerExtension extends PhysicsServer3DExtension:

    func _body_create():
        # Your custom body creation logic here
    func _shape_create():
        # Your custom shape creation logic here

Handling Physics Bodies

Within our custom physics extension, we’ll need to manage physics bodies. These can be rigid bodies, static bodies, or other types. Here’s how you might set up a method to create and return the unique ID for a new rigid body:

class MyPhysicsServerExtension extends PhysicsServer3DExtension:
    func _body_create(mode = 2): # Rigid body mode is 2 by default
        var body_id = ... # Generate a unique ID for the body
        # Initialize body properties here
        return body_id

Now, we’ll look at applying forces to these bodies, which is critical for making our physics interactive and dynamic.

func _body_apply_force(body_id, force, position = Vector3()):
    # Apply force to the body identified by body_id at the given position
func _body_apply_impulse(body_id, impulse, position = Vector3()):
    # Apply an impulse to the body identified by body_id at the given position

We need these functionalities to interact with objects in the game world. For instance, when a player hits an object, we can use _body_apply_impulse to simulate that hit’s impact.

Defining Collision Shapes

Collision shapes are essential for physics interactions. They define the boundaries that objects cannot pass through. Here’s how we can extend the PhysicsServer3DExtension to create different shapes:

func _shape_create(type):
    var shape_id = ... # Generate a unique ID for the shape
    # Setup the shape according to the type
    return shape_id

func add_box_shape(shape_id, half_extents):
    # Configures a box shape for collision detection

func add_sphere_shape(shape_id, radius):
    # Configures a sphere shape for collision detection

Having these functions allows us to specify the physical boundaries of the objects in our game, ensuring that they interact with the world as expected.

Managing Physics Queries

Physics queries are an essential part of any physics system, allowing us to ask questions about our game world—such as whether two shapes are colliding or if there’s a body within a certain area. Here’s how you might manage raycast queries in your custom extension:

func _intersect_ray(from, to, exclude = [], collision_layer = 0xFFFFFFFF, collide_with_bodies = true, collide_with_areas = false):
    # Check if a ray from point 'from' to point 'to' intersects with any objects

With these methods in place, you can begin to see how your custom physics server can manage complex interactions and provide detailed information regarding the physical state of the game world, thereby giving you the control needed to create realistic and immersive gameplay mechanics. Remember, these are just foundational elements; from here, you can expand and customize further to fit the specific physics needs of your project.Let’s continue to expand the capabilities of our custom physics extension by looking at how we can manage shapes and collisions further. Understanding how to modify shapes and check for collisions are fundamental components for any physics system to be practical and useful within a game.

Modifying Collision Shapes

In our custom physics server, we may need to modify shapes during the game. Here’s how to resize a box shape dynamically:

func set_box_shape_size(shape_id, half_extents):
    # Modify the size of a box shape based on the provided half_extents
    # Placeholder for actual resizing logic

Detecting when shapes intersect or when bodies enter or exit certain areas is crucial for gameplay mechanics like triggering events or applying effects:

func _body_test_motion(body_id, from_position, to_position, motion, margin = 0.08):
    # Test if a body moving from 'from_position' to 'to_position' would hit something.
    # Placeholder for actual motion testing logic

While handling collisions, we often need to get detailed information on contact points, normal force, and the colliding bodies. To achieve this, we can define methods to gather the collision information:

func _body_get_direct_state(body_id):
    # Retrieve information about a body's direct state, such as position, rotation, etc.
    # Placeholder for getting body's state

func _area_get_overlapping_bodies(area_id):
    # Get a list of bodies overlapping the specified area
    # Placeholder for retrieval logic

Custom Constraints and Joints

Custom physics extension also allows us to create constraints and joints, which can be used to connect physics bodies in interesting ways:

func _joint_create_hinge(body_id_a, hinge_position_a, body_id_b, hinge_position_b):
    # Create a hinge joint between two bodies

func _joint_set_param(joint_id, parameter, value):
    # Set specific parameters on joints, such as bias or limits

These methods let you introduce complex behavior like swinging doors, ragdoll characters, or connected chains within your game world.

Advanced Simulation Control

Finally, to fully leverage the custom physics engine, we might want to provide direct control over the physics simulation itself:

func _physics_step(delta):
    # Directly step the physics state forward by the given delta time
    # Placeholder for stepping simulation logic

By directly controlling the step function, developers have the opportunity to implement custom time scaling, paused states, or debugging tools that can slow down or speed up the simulation on demand.

With these functionalities at your fingertips, you’re equipped to craft a robust and finely-tuned physics system within your Godot games. By extending the PhysicsServer3D class, you are no longer constrained by the default physics behaviors, unlocking the potential to deliver unique and engaging gameplay experiences to players. Dive into the world of custom physics with Godot, where your imagination is the limit to what you can create!As we dive deeper into the capabilities of the custom physics extension, let’s explore more advanced functionalities, such as handling more intricate joints, simulating soft bodies, and even managing the physics environment itself.

Advanced Joints and Constraints

In more complex physics simulations, you may want to use different types of joints that offer more control and variety in the behavior of connected bodies. Here is an example of how you might implement a pin joint, allowing two bodies to rotate freely around a shared anchor:

func _joint_create_pin(body_a, body_b, anchor):
    # Create a pin joint connecting 'body_a' and 'body_b' at 'anchor' position

For scenarios where you require a joint that only allows movement along a single axis, a slider joint can be the perfect fit. Here’s a potential implementation:

func _joint_create_slider(body_a, body_b, axis):
    # Create a slider joint defining movement along 'axis' for 'body_a' and 'body_b'

Adding motors or springs to joints can create dynamics like automatic opening doors or suspension in vehicles. Here’s a code snippet for a motorized hinge joint:

func _joint_set_hinge_motor(joint_id, velocity, torque):
    # Set a hinge joint to be motorized with the given 'velocity' and 'torque' parameters

Soft Body Simulation

Soft bodies are entities that deform in a realistic manner when forces are applied. They are perfect for simulating substances like cloth, jelly, or muscles. Let’s look at how this might be approached in code:

func _soft_body_create():
    # Create a new soft body instance and return its id
func _soft_body_add_point(soft_body_id, position):
    # Add a point to the soft body at the given 'position'

func _soft_body_set_link(soft_body_id, point_index_a, point_index_b):
    # Create a link between two points in a soft body

Physics Environment Management

Your custom physics simulation may also require control over the overall physics environment. You might want to adjust properties like gravity or damping:

func _environment_set_gravity(gravity_vector):
    # Set the global gravity for the physics environment
func _environment_set_damping(damping_value):
    # Set global damping to slow down motion over time

Collision Layers and Masks

To fine-tune which objects collide with which, you can make use of layers and masks. They allow you to define groups of objects that should interact, simplifying complex simulations:

func _body_set_collision_layer(body_id, layer):
    # Set the collision layer for 'body_id' to dictate its collision group

func _body_set_collision_mask(body_id, mask):
    # Set the collision mask for 'body_id' to determine what it collides with

Querying the Physics State

Finally, understanding the current state of your physical simulation is often as important as influencing it. Here are some methods you may implement to query the physics state:

func _body_get_position(body_id):
    # Retrieve the current position of the body with 'body_id'

func _body_get_velocity(body_id):
    # Get the current velocity of a specific body

func _area_get_space_override_mode(area_id):
    # Find out the space override mode for the area with 'area_id'

By integrating these methods, you provide a full suite of control over the physics in your Godot project. You’re not only setting states but also actively querying and retrieving information that can inform gameplay decisions, enhance visual feedback, or debug your physics simulations. With the PhysicsServer3DExtension, the depth and precision of your game’s physical interactions are bounded only by your imagination and how far you’re willing to customize your physics server. Happy coding!

Where to Go Next with Your Godot Learning Journey

Now that you’ve dipped your toes into the possibilities of extending Godot’s PhysicsServer3D with custom behaviors, you’re likely itching to explore more of what Godot 4 has to offer. We at Zenva know that the journey of learning and mastering game development is an ongoing adventure, and we’re here to guide you every step of the way.

To continue expanding your knowledge and skills, we highly recommend checking out our Godot Game Development Mini-Degree. This comprehensive program is perfect for harnessing the power of Godot 4 to create your own cross-platform games, taking you from beginner to advanced levels at your own pace. With a slew of topics that cover the essentials of game development, you’ll have the opportunity to build a solid foundation and create a portfolio of impressive projects.

If you’re looking for a broader look at what we offer for Godot enthusiasts, then look no further than our full collection of Godot courses. Each course is designed with flexibility and practicality in mind, making it easy for you to learn and practice at your convenience. Enhance your skills, earn certificates, and open up new opportunities in the game development industry with Zenva. Keep learning, creating, and achieving your game development dreams!


Embracing the PhysicsServer3DExtension class in Godot 4 is akin to unlocking a secret level in your game development journey—it empowers you to push the boundaries of physics simulations, bringing an exceptional level of realism and complexity to your games. We hope that this peek into the expansive world of custom physics has sparked your creativity and bolstered your desire to learn and master even more. Remember, every line of code you write is a step towards transforming the game ideas swirling in your imagination into captivating digital realities.

At Zenva, we’re passionate about fueling your growth and success in game development. Our Godot Game Development Mini-Degree is just the first play in your playbook of creating awe-inspiring games. So, leap into action, continue honing your skills with us, and carve your path into the thrilling universe of game development. The power to build stunning games is at your fingertips—seize it!

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