CollisionPolygon3D in Godot – Complete Guide

Welcome to today’s tutorial on the CollisionPolygon3D class in Godot Engine 4! If you’re delving into the world of 3D game development with Godot, understanding collision shapes is essential. Collision detection is a fundamental aspect that can make or break the gameplay experience. Through this tutorial, we’re going to explore the capabilities of the CollisionPolygon3D node, and you’ll learn how to leverage this tool to create interactive and solid objects within your game scenes. Let’s dive in and unlock the potential of collision shapes in your Godot projects!

What is CollisionPolygon3D?

CollisionPolygon3D is a versatile node provided by Godot 4 that allows game developers to create thickened polygon shapes, akin to prisms, which can be used for collision detection. This node is a child of CollisionObject3D, meaning it can be used to add a detection shape to Area3D nodes or to construct collidable volumes for PhysicsBody3D nodes, turning them into solid objects that can interact with other elements in a 3D environment.

What is it for?

CollisionPolygon3D serves as the backbone for defining the spatial extent of objects in a game world where they need to interact physically. Whether that’s restricting a player’s movement, triggering events when an object enters a certain area, or simulating physics between objects, CollisionPolygon3D provides an intuitive way to outline the collision boundaries which can be both concave and convex.

Why Should I Learn It?

Grasping the concept of CollisionPolygon3D can be quite empowering for a game developer. By learning to work with this class, you can create more accurate and optimized collision shapes for your game objects, leading to better performance and a more realistic gaming experience. Additionally, understanding collision detection is critical if you aim to design games that require precise interactions between objects, such as puzzles, platformers, or simulation games. Let’s get ready to jump into the practical side of things and begin creating with CollisionPolygon3D!

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Setting Up the CollisionPolygon3D

To begin using the CollisionPolygon3D node in your project, you first need to create an instance of this node and set it up appropriately. Here’s how to do it from the Godot editor:

var collision_polygon = CollisionPolygon3D.new()
collision_polygon.set_polygon([
    Vector3(0, 0, 0),
    Vector3(0, 1, 0),
    Vector3(1, 1, 0),
    Vector3(1, 0, 0)
])
add_child(collision_polygon)

This code will create a simple quad as a collision shape. The `set_polygon` method takes an array of `Vector3` points defining the polygon in 3D space.

Configuring Collision Shapes

You can tweak the polygon to be more complex or fit different shapes based on your game’s requirements. For more intricate shapes, you just need to provide more points:

collision_polygon.set_polygon([
    Vector3(0, 0, 0),
    Vector3(0, 0, 1),
    Vector3(1, 0, 1),
    Vector3(1, 0, 0),
    Vector3(0.5, 1, 0.5)
])

This snippet defines a pyramid-shaped collision volume. Note that the points should define a convex shape or be part of a concave decomposition.

Adding a CollisionPolygon3D to a PhysicsBody3D

To interact with other physics objects, the CollisionPolygon3D must be a child of a PhysicsBody3D node. Here’s an example creating a StaticBody with a custom collision shape:

var static_body = StaticBody3D.new()
var collision_polygon = CollisionPolygon3D.new()
collision_polygon.set_polygon([
    Vector3(0, 0, 0),
    Vector3(0, 1, 0),
    Vector3(1, 1, 0),
    Vector3(1, 0, 0)
])
static_body.add_child(collision_polygon)
add_child(static_body)

With this code, the static body now includes the collision polygon, making it part of the physics world.

Adjusting Depth for CollisionPolygon3D

The thickness or depth of your collision polygon is an important parameter when creating collidable 3D volumes. Adjusting the depth can be done using the `depth` property.

collision_polygon.depth = 5.0

This code sets the depth of your collision polygon to 5 units. It’s crucial when turning your flat polygon into a 3D collidable object.

Remember to always consider performance when creating and adding your collision shapes as complex shapes can make the physics engine do more work than necessary. Stick to as simple a shape as possible that adequately represents the collidable volume of your object.Continuing from where we left off, let’s explore more functionalities of the CollisionPolygon3D and how it can be manipulated and used effectively within Godot Engine 4.

In some cases, you might start with a primitive shape but need to add or remove points to fine-tune the collision shape. To do this, Godot offers methods to modify the polygon points directly.

Modifying Collision Polygon Points

Here’s how you can add a point to an existing collision polygon:

// Assuming collision_polygon is a previously defined CollisionPolygon3D instance
var points = collision_polygon.polygon
points.append(Vector3(2, 0, 0))
collision_polygon.polygon = points

When you need to remove a point, you can do so by manipulating the `polygon` array:

// Remove the last point
points.remove(points.size() - 1)
collision_polygon.polygon = points

The CollisionPolygon3D can also be created and associated with different PhysicsBody3D types. Let’s see how this works with a RigidBody3D, for dynamic physics interactions.

Example with RigidBody3D

To set up a dynamic object that responds to physics forces, we add a CollisionPolygon3D to a RigidBody3D:

var rigid_body = RigidBody3D.new()
var collision_polygon = CollisionPolygon3D.new()
collision_polygon.set_polygon([ ... ]) // Provide your points here
rigid_body.add_child(collision_polygon)
add_child(rigid_body)

In this setup, the RigidBody3D will react to gravity, collisions, and other forces. The CollisionPolygon3D defines the shape those forces act upon.

Working with Collisions

To react to collision events, you can connect signals from the PhysicsBody3D nodes. Here’s an example of how to connect a signal for when the body enters a collision:

func _ready():
    static_body.connect("body_entered", self, "_on_body_entered")

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

In this script, `_on_body_entered` will be called anytime another physics body collides with our static body that has the collision polygon.

Sometimes, you may need to adjust the collision layer or mask of your CollisionPolygon3D. This ensures that collisions only occur between specific objects.

Setting Collision Layers and Masks

Assigning your object to collision layers and setting its collision mask can be done like this:

static_body.collision_layer = 1
static_body.collision_mask = 1

With this setting, `static_body` exists in layer 1 and will only collide with objects whose mask includes layer 1.

Lastly, since Godot 4 uses a modern rendering engine with improved graphics, it’s vital to make sure collision shapes are not visible in the final game, unless it’s for debugging purposes.

# Disable visibility for the collision shape
collision_polygon.visible = false

Now your collision polygons are invisible during gameplay, providing collision detection without affecting the visuals.

These examples should give you a clearer picture of how to use CollisionPolygon3D nodes within the Godot engine. Experimenting with these nodes can significantly contribute to the behavior and interactivity of your 3D game, so don’t hesitate to explore their features and functionalities. Remember, at Zenva, we strive to empower our learners with the knowledge they need to create amazing and interactive experiences with tools like Godot. Happy coding!Working with collision polygons often involves real-time modifications, which can enhance gameplay by changing the environment or the properties of game objects. Below are additional examples showcasing how you can make the most of the CollisionPolygon3D node in Godot Engine 4.

You can change the collision polygon’s points live, in response to game events, such as an explosion that alters the terrain’s shape.

func deform_terrain(impact_point: Vector3, radius: float):
    var points = collision_polygon.polygon
    for i in range(points.size()):
        if points[i].distance_to(impact_point) < radius:
            # Push the point upwards, simulating a crater
            points[i] += Vector3(0, -1, 0)
    collision_polygon.polygon = points

In this code, we iterate over each point in the collision polygons and, if it’s within a certain radius of the impact point, we move it to simulate a crater.

You might also want to enable or disable a CollisionPolygon3D based on game logic, such as a bridge that can be toggled on or off.

func toggle_bridge(active: bool):
    collision_polygon.disabled = !active

By changing the `disabled` property, you can turn collision detection on or off for that particular shape.

For performance reasons, or to create puzzles where only certain parts of an object can be collided with, you can even break a complex shape into multiple collision polygons.

# Assume parent_object is a loaded 3D object that requires multiple collision shapes
func create_multiple_collision_shapes(parent_object):
    for shape_description in parent_object.shape_descriptions:
        var new_collision_polygon = CollisionPolygon3D.new()
        new_collision_polygon.set_polygon(shape_description.points)
        parent_object.add_child(new_collision_polygon)

Here we iterate through multiple shape descriptions and add a new collision polygon for each. This allows for more granular collision detection.

In some cases, you might also want to change an object’s collision layer in real-time, potentially to phase through certain objects or interact with different groups of physics bodies.

# Shift the object to collision layer 2
static_body.collision_layer = 1 << 1
# Now the object will only interact with objects whose masks include layer 2

This is particularly powerful for games involving stealth, where detection might depend on which layer the player is in.

Finally, you can leverage the 3D physics engine by responding to the speed and angle of collisions to create more dynamic reactions.

# Ensure this function is connected to the "body_entered" signal
func _on_body_entered(body):
    var relative_velocity = body.linear_velocity - rigid_body.linear_velocity
    if relative_velocity.length() > 10:
        # The collision was hard, react accordingly
        handle_hard_collision(body)

In this snippet, we’re using the relative velocities of two colliding bodies to determine the intensity of a collision.

These examples should provide further insight into the dynamic nature of collision detection using CollisionPolygon3D in Godot 4. As always, these techniques are tools for you, the developer, to create engaging and interactive experiences. Experiment with CollisionPolygon3D and other Godot features to discover new gameplay possibilities. Remember, with Zenva, you’re always expanding your skillset to bring your creative visions to life in the world of game development!

Embark Further On Your Game Development Journey

With the foundational knowledge of CollisionPolygon3D in Godot 4, you’re well on your way to mastering 3D game creation. If you’re keen to expand your skills and take your learning to the next level, the Godot Game Development Mini-Degree at Zenva Academy is a perfect next step. Our tailored curriculum will guide you through the diverse aspects of game development with Godot, covering both 2D and 3D games.

Whether you’re just starting or looking to polish your skills, you’ll find structured and comprehensive courses within the Mini-Degree to help you construct engaging gameplay experiences. And, for a truly robust array of Godot learning materials, our catalog of Godot courses will serve as an invaluable resource. Dive into our extensive, project-based lessons at your own pace, and join the ranks of learners who’ve used their Zenva training to publish games, advance their careers, and even start their own businesses. Continue your game development adventure with us, and bring your creative visions to life in the world of Godot.

Conclusion

Today, you’ve not only begun to unravel the intricacies of the CollisionPolygon3D node in Godot Engine 4, but you’ve also taken a solid step towards enhancing your game development skills. Practical knowledge on collision detection and physics interactions will not only enrich your current projects but also empower you to conceive and execute more complex game ideas in the future. As you continue experimenting and implementing these nodes, remember that every feature and line of code carries the potential to elevate your game’s interactivity and realism.

We at Zenva are excited to accompany you on your journey of discovery in the realm of game development. If you feel inspired and ready to delve deeper, our Godot Game Development Mini-Degree awaits to offer you a structured path through the essential skills and advanced techniques necessary for creating compelling game experiences. Embrace this learning opportunity, and let’s build amazing games together!

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