Projection in Godot – Complete Guide

Projection in game development is like the gateway between the 3D world your characters inhabit and the 2D screen through which players experience the adventure. Understanding how to harness the power of projection enables you to determine not just what players see, but how they see it, crafting perspectives that can amplify storytelling, gameplay, and visual impacts. Today, we’ll delve into the Projection class in Godot 4, a tool central to the art of bringing three-dimensional spaces into the two-dimensional plane of our screens.

What is the Projection Class?

The Projection class is a cornerstone of 3D graphics in Godot 4, fundamental in rendering a 3D scene onto a 2D view. It’s a 4×4 matrix specifically crafted for projective transformations, which include common operations such as translation, rotation, scaling, shearing, and most crucially, perspective transformations.

What is it used for?

The Projection class is incredibly versatile, used internally by Camera3D to calculate how a 3D scene is visually represented on your screen. Whether you’re crafting an expansive open world, a tight isometric strategy game, or an immersive VR experience, projection matrices are the mathematical magicians that map the coordinates of your game’s geometry to pixel positions on the screen.

Why Should I Learn It?

Grasping the concept of projection is essential for any game developer delving into the 3D realm. By understanding projection, you gain the ability to customize the player’s point of view, modify the level of depth and perspective, and even tailor the visual experience for different devices, such as VR headsets. Learning about the Projection class gives you the key to unlock a higher level of control and optimization for your Godot games.

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Manipulating Projection Matrices in Godot 4

To effectively manipulate the Projection class in Godot 4, you’ll need to be familiar with a few important functions. Each code example will address a different aspect of how you can tailor the projection matrix to suit your game’s unique needs.

Setting Up the Camera

Before we dive into projection matrices, let’s start with initializing a Camera3D node, since it’s the primary user of the Projection class:

var camera = Camera3D.new()
add_child(camera)
camera.current = true

Now that we have a camera in place, we can set up the projection matrix.

Creating a Perspective Projection

A perspective projection creates a sense of depth, with objects appearing smaller as they are further away. Here’s how you set up a perspective matrix:

var fov = 70.0  # Field of View in degrees
var aspect_ratio = OS.window_size.x / OS.window_size.y
var z_near = 0.1
var z_far = 100.0

camera.set_perspective(fov, aspect_ratio, z_near, z_far)

This sets up the camera with a typical perspective projection, using the field of view, aspect ratio of the window, and near/far planes.

Switching to an Orthographic Projection

For 2D-style views or isometric games, you may prefer an orthographic projection where object sizes remain constant, regardless of depth. To set this up:

var size = 2
var aspect_ratio = OS.window_size.x / OS.window_size.y
var z_near = -10
var z_far = 10

camera.set_orthogonal(size, aspect_ratio, z_near, z_far)

Adjusting Field of View

Adjusting the field of view (FOV) can simulate zoom effects or adapt the vision for wider screens. Here’s a simple way to modify it:

var new_fov = 60.0
camera.set_perspective(new_fov, aspect_ratio, z_near, z_far)

Changing the FOV to 60 degrees narrows the camera’s vision, zooming in slightly on the scene.

Custom Projection Matrices

Sometimes you may want to create a custom projection matrix. This can be done with the `set_frustum()` method or by setting the projection matrix directly:

# Set a frustum projection directly.
camera.set_frustum(45.0, aspect_ratio, z_near, z_far, Vector2(0.0, 0.0))

# Or set a custom projection matrix.
var custom_proj_mat = Transform(
    Basis(),
    Vector3()
).as_project_mat4()
camera.projection_matrix_custom = custom_proj_mat

In these examples, we either define a frustum directly or create a custom transform and convert it to a 4×4 matrix for the camera’s use.

By understanding and applying these code snippets, developers can significantly alter the visual experience of their games. Remember, the way you set up your camera’s projection can define the feel of your game, from a tightly controlled isometric strategy game to a fast-paced first-person shooter with a wide field of view.Certainly! Let’s delve into more sophisticated manipulations of the Projection class to empower our Godot 4 creations with advanced visual techniques.

Adjusting the Aspect Ratio

When your game runs on various devices, you might need to account for different screen sizes. Here’s how you adjust the camera’s aspect ratio on-the-fly:

var new_aspect_ratio = OS.window_size.x / OS.window_size.y
camera.set_perspective(fov, new_aspect_ratio, z_near, z_far)

This recalculates the projection matrix to accommodate a new window size, maintaining correct proportions.

Camera Movement and Projection

Changing camera position and rotation affects the projection. Here’s how to move the camera while maintaining the projection matrix:

camera.translation = Vector3(5, 2, -10)
camera.rotation_degrees = Vector3(30, 45, 0)

This snippet positions the camera at coordinates (5, 2, -10) and rotates it to look at an angle, giving a new perspective.

Zoom with Orthographic Projection

To implement zoom functionality with orthographic projection, we simply change the ‘size’ parameter:

var zoom_level = 1.5
camera.set_orthogonal(size / zoom_level, aspect_ratio, z_near, z_far)

Camera Viewport Size

For split-screen games or specific visual effects, you might want to manipulate the camera’s viewport size directly:

var viewport_rect = Rect2(0, 0, 1024, 768)
camera.viewport_rect = viewport_rect

This code sets the camera’s viewport to a 1024×768 rectangle, which could represent a section of a split-screen setup.

Projection Matrices for VR

Virtual reality headsets often require specific projection matrices to account for lens distortion:

# Usually obtained from VR API or headset SDK
var hmd_projection_left = Transform() # Placeholder for VR API call
var hmd_projection_right = Transform() # Placeholder for VR API call

camera.projection_matrix_custom = hmd_projection_left.as_project_mat4()
# And similarly for the right eye's camera

This is a placeholder for how you’d set different projection matrices for each eye in a VR setup, with specific transforms usually provided by the VR SDK.

Manipulating Field of View in Real-Time

To create dynamic effects like a sniper scope or a character focusing, you might want to manipulate the FOV during gameplay:

func _process(delta):
    var target_fov = is_aiming ? 30.0 : 70.0
    fov = lerp(fov, target_fov, delta * zoom_speed)
    camera.set_perspective(fov, aspect_ratio, z_near, z_far)

This function smoothly transitions the FOV over time between a wide and narrow field of view, controlled by a boolean `is_aiming`.

Through these examples, you can see the depth of control developers have over the camera system in Godot 4. By managing projection matrices, you are not just altering visuals, but you’re enhancing gameplay and immersion, ultimately crafting a more engaging player experience. Whether you’re manipulating FOV for dramatic effect, adjusting views for split-screen cooperation, or ensuring your game looks amazing on every screen, Godot 4’s Projection class equips you with the necessary tools to do so.Of course, let’s delve deeper into the Projection class’s capabilities, providing more nuanced control over the visual representation of your 3D scenes in Godot 4.

Dynamic Perspective Distortion

Sometimes, an artistic direction may call for non-standard perspective effects, like a fisheye lens or other forms of distortion. Customizing the projection matrix directly can achieve these results:

var custom_perspective_matrix = camera.get_projection_matrix()
custom_perspective_matrix[2][0] = 0.2 # Horizontal distortion
custom_perspective_matrix[2][1] = 0.1 # Vertical distortion
camera.projection_matrix_custom = custom_perspective_matrix

The example above introduces horizontal and vertical skew into the camera’s projection, simulating a subtle distortion effect. You can experiment with these values for different artistic effects.

Responding to Window Resize Events

For games that may be played in windowed mode, it’s important to handle window resize events to ensure the projection matrix is always correct:

func _notification(what):
    if what == MainLoop.NOTIFICATION_WM_SIZE_CHANGED:
        var new_aspect_ratio = OS.window_size.x / OS.window_size.y
        camera.set_perspective(fov, new_aspect_ratio, z_near, z_far)

This code snippet automatically updates the camera’s aspect ratio whenever the window size changes, maintaining the intended visual appearance.

Creating Off-Center Projections

For certain types of games, for example, ones with HUD elements or asymmetric multiplayer setups, you may wish to use an off-center projection:

# Define the off-center margins
var margin_left = -1.0
var margin_right = 1.0
var margin_bottom = -1.0
var margin_top = 1.0

camera.set_frustum(fov, aspect_ratio, z_near, z_far, Vector2(margin_left, margin_top), Vector2(margin_right, margin_bottom))

This sets up a frustum that’s off-center, allowing UI or other screen-space elements to occupy part of the screen without affecting the primary view.

Projection Matrix Manipulation for Effects

Projection matrices can be animated or adjusted over time for cinematic effects, like a sudden zoom or transitioning from one type of projection to another:

# Animate to a new field of view over time
tween.interpolate_property(camera, "fov", camera.fov, new_fov, 1.0, Tween.TRANS_LINEAR, Tween.EASE_IN_OUT)
tween.start()

Here, a Tween node animates the FOV property of the camera, creating a smooth zoom effect.

Adjusting View Distance

Managing the range of your camera’s view can have significant performance implications, especially for expansive 3D worlds:

# Set a shorter view distance for fog or performance reasons
var new_z_near = 0.5
var new_z_far = 50.0
camera.set_perspective(fov, aspect_ratio, new_z_near, new_z_far)

This snippet adjusts the near and far planes of the camera, potentially improving performance by not rendering objects that are too far to be seen clearly.

Relaying Projection Data to Shaders

For advanced visual effects, shaders may require access to projection information. Here’s how you might pass it along:

# Access the current projection matrix
var proj_matrix = camera.get_projection_matrix()

# Set the shader parameter accordingly
material.set_shader_param("projection_matrix", proj_matrix)

By setting a shader parameter, you can use the current state of the projection matrix within your shader code for various effects like screen-space reflections or refractions.

By harnessing these code snippets and techniques, game developers can finetune their 3D games in Godot 4 to achieve a desired aesthetic or solve technical challenges. The manipulation of the Projection class extends far beyond simple perspective alterations, influencing performance, artistic direction, and gameplay mechanics. Whether you are working on intricate cutscenes, optimizing for various display resolutions, or crafting unique visual effects, Godot’s Projection class gives you the power to implement your vision precisely as intended.

Take Your Godot Skills Further

Embarking on your journey through Godot 4’s Projection class is just the beginning of what you can create and explore with this powerful game engine. To keep advancing your skills and bringing your own game ideas to life, we at Zenva offer a curated learning path through our Godot Game Development Mini-Degree. This collection of carefully crafted courses is designed to equip you with the knowledge to build engaging cross-platform games, covering not only the foundational principles but also delving deep into more complex game mechanics.

Whether you’re just starting out or refining your development prowess, our project-based curriculum supports your growth at every step. And if you’re looking for a broader range of tutorials, our comprehensive list of Godot courses provides in-depth content on a variety of topics, ensuring there’s always something new to learn.

At Zenva, we’re passionate about helping you transform your creative visions into playable realities. Join us and step into a community of learners, creators, and innovators – and take your next step toward professional game development with the support of our extensive resources.

Conclusion

Unlocking the secrets of the Projection class in Godot 4 is a testament to your dedication to mastering game development. With these newfound skills, you’re well on your way to sculpting immersive worlds that captivate players’ imaginations. Remember, the more you experiment with projection matrices, the more command you’ll have over the visual storytelling of your game. We at Zenva encourage you to push the boundaries of what you can achieve, and we’re here to support you every step of the way.

Are you ready to revolutionize your understanding and elevate your game creations to unprecedented heights? Dive deeper into the realm of Godot with our Godot Game Development Mini-Degree. Let us guide you through each challenge and triumph as you turn your gaming dreams into interactive realities. The quest for knowledge never ends, and with Zenva, you’re always one step closer to fulfilling your game development ambitions.

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