RDUniform in Godot – Complete Guide

Diving into the world of game development can be an exhilarating experience, especially when you start experimenting with the intricate systems that drive modern games. One of the powerful tools at your disposal is Godot 4, a versatile game engine that enables creators to bring their visions to life. In this tutorial, we’ll explore the RDUniform class, a crucial component of Godot 4 that deals with shader uniforms. As we unpack the features and functionalities of RDUniform, you’ll see how it contributes to the flexibility and efficiency of your rendering pipeline.

What Is RDUniform?

RDUniform stands for Rendering Device Uniform in Godot 4. It is a class that inherits from RefCounted, itself a derivative of the Object class within the Godot Engine’s robust hierarchy. The RDUniform class acts as a container for shader uniform data, which is used by the RenderingDevice. But what exactly is a “uniform”?

What Is It For?

Uniforms are a type of shader variable that remain constant across all rendering of a single draw call. They’re utilized to convey the same piece of information to every vertex or fragment processed by the shader. Think of them as the constants or settings for your shader’s calculations, controlling everything from color and lighting intensity to transformation matrices and other critical graphic elements.

Why Should I Learn About RDUniform?

Understanding RDUniforms is essential for developing visually stunning and high-performance graphics within your Godot 4 projects. They not only allow you to optimize your shaders by batching draw calls and reducing state changes but also offer a way to keep your code clean and manageable. Learning to use RDUniform effectively empowers you to:

– Modify the appearance of objects on the fly.
– Enhance the realism of your scenes with dynamic lighting and effects.
– Fine-tune the graphical output of your game for various hardware architectures.

By grasping the RDUniform class, you gain deeper insight into game engine internals, improving both your development workflow and the quality of your final product.

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Creating and Configuring an RDUniform

To start using RDUniform in Godot 4, you must first create an instance of the class. This can be done like any other object in Godot. Once you have an instance, configuration is key. Let’s look at how to set up a basic RDUniform for a custom shader.

var uniform = RDUniform.new()
uniform.type = RDUniform.UNIFORM_TYPE_FLOAT
uniform.name = "time"
uniform.set_float_value(1.0)

Here, we’ve created a new RDUniform and set its type to `UNIFORM_TYPE_FLOAT`, which means this uniform will contain a single floating-point value. We then give it a name, “time”, which we will refer to in our shader. Lastly, we initialize it with a default value of 1.0.

Updating Uniform Values

Once your uniform is configured, you will often need to update its value as your game or application runs. For instance, you might want to animate a material by changing a uniform value every frame.

var time_passed = OS.get_ticks_msec() / 1000.0
uniform.set_float_value(time_passed)

In the above code, we set the uniform’s value to the number of seconds that have passed since the game started. This is a common technique for creating time-based animations in shaders.

Working with Vectors and Matrices

Shaders often require more complex data types like vectors and matrices. RDUniform can handle these as well. Here’s how you can create a uniform for a 4×4 transform matrix:

var transform_uniform = RDUniform.new()
transform_uniform.type = RDUniform.UNIFORM_TYPE_TRANSFORM
transform_uniform.name = "model_matrix"
transform_uniform.set_transform_value(Transform())

And here’s an example of setting a uniform to a vector3 value, which could be used for a color or position:

var color_uniform = RDUniform.new()
color_uniform.type = RDUniform.UNIFORM_TYPE_VEC3
color_uniform.name = "albedo_color"
color_uniform.set_vec3_value(Color(1, 0, 0))  // Set to red

This code initializes a new RDUniform for a 3D vector and sets its default value to red.

Passing Uniforms to Shaders

Finally, after setting up your uniform, you’ll need to pass it to your shader. This involves working with the RenderingDevice API and shader resources.

var shader = RDShader.new()
var uniform_array = [uniform]
var shader_id = RenderingDevice.shader_create()
RenderingDevice.shader_set_code(shader_id, shader_code)
RenderingDevice.shader_set_uniforms(shader_id, uniform_array)

This snippet creates a new shader resource, sets its shader code, and then passes the uniform array to the shader. This is a simplified example, but it shows the basic process of binding uniforms to shaders in Godot 4.

Through these examples, you should now have a foundation for using RDUniform with your custom shaders in Godot 4. Experiment with these snippets and see how they affect the shading in your projects!Adding Samplers to RDUniforms

In addition to simple values like floats and vectors, shaders often need to use textures. In Godot 4, you can pass texture data to a shader using RDUniform and a sampler type. Here’s how to create a sampler RDUniform:

var texture_uniform = RDUniform.new()
texture_uniform.type = RDUniform.UNIFORM_TYPE_SAMPLER
texture_uniform.name = "diffuse_texture"
texture_uniform.set_texture_value(your_texture_resource)

In this example, `your_texture_resource` would be a reference to a Texture resource that contains the image data you want to use in your shader.

Binding Multiple Uniforms

Often, you’ll want to pass several uniforms into a shader at once. Here’s how you might update and bind multiple uniforms before drawing:

var time_uniform = RDUniform.new()
time_uniform.type = RDUniform.UNIFORM_TYPE_FLOAT
time_uniform.name = "time"
time_uniform.set_float_value(OS.get_ticks_msec() / 1000.0)

var resolution_uniform = RDUniform.new()
resolution_uniform.type = RDUniform.UNIFORM_TYPE_VEC2
resolution_uniform.name = "resolution"
resolution_uniform.set_vec2_value(Vector2(screen_width, screen_height))

var uniforms = [time_uniform, resolution_uniform, texture_uniform]
RenderingDevice.shader_set_uniforms(shader_id, uniforms)

This code block updates the time uniform, creates a new uniform for screen resolution, and then binds both of these along with the previously created texture_uniform to the shader.

Dynamic Uniform Updates

In some cases, you might want to update uniforms based on user input or other events. Here’s an example of how you might update a uniform when the player fires a weapon in a game:

func on_weapon_fire(bullet_speed: float):
    var bullet_speed_uniform = RDUniform.new()
    bullet_speed_uniform.type = RDUniform.UNIFORM_TYPE_FLOAT
    bullet_speed_uniform.name = "bullet_speed"
    bullet_speed_uniform.set_float_value(bullet_speed)
    
    var uniforms = [bullet_speed_uniform]
    RenderingDevice.shader_set_uniforms(shader_id, uniforms)

Each time the weapon is fired, the bullet_speed uniform is updated with the new value, which can then affect the rendering of the bullet in the scene.

Optimizing Uniform Changes

To minimize performance overhead, it’s important to only update and bind uniforms when necessary. Here’s an example of a condition where you might check if an update is needed:

func update_uniform_if_changed(uniform: RDUniform, new_value):
    if uniform.get_float_value() != new_value:
        uniform.set_float_value(new_value)
        RenderingDevice.shader_set_uniforms(shader_id, [uniform])

This function updates the uniform and rebinds it to the shader only if the value has changed, reducing unnecessary calls to the graphics API.

Texture Array Samplers

For more complex shader operations, you may need to use texture arrays. These allow you to pass an array of textures into a shader and select which one to use during rendering:

var texture_array_uniform = RDUniform.new()
texture_array_uniform.type = RDUniform.UNIFORM_TYPE_SAMPLER_ARRAY
texture_array_uniform.name = "texture_array"
texture_array_uniform.set_texture_array_value(your_texture_array_resource)

With this setup, `your_texture_array_resource` would be a reference to a TextureArray resource containing multiple textures that the shader can use.

By incorporating these examples into your Godot 4 projects, you’ll be able to leverage the power of uniforms to control your shader’s behavior dynamically and efficiently. Keep practicing and experimenting with RDUniforms to find new and creative ways to enhance the visual appeal of your game or application!Incorporating Textures with 3D Transform

Uniforms can also pass specific transformation information for your textures. This is particularly handy when you need to scale, rotate, or translate a texture within a shader:

var texture_transform_uniform = RDUniform.new()
texture_transform_uniform.type = RDUniform.UNIFORM_TYPE_TRANSFORM
texture_transform_uniform.name = "texture_transform"
texture_transform_uniform.set_transform_value(Transform(Basis(), Vector3(0.5, 0.5, 0)))

// Apply a half-scale transformation to the texture
RenderingDevice.shader_set_uniforms(shader_id, [texture_transform_uniform])

In this code, we create a uniform that contains a transformation, which, when applied, will scale the texture by half along the X and Y axis.

Handling Directional Lights

For 3D scenes, to add the effect of directional lighting, we might pass the light direction and color through uniforms:

var light_dir_uniform = RDUniform.new()
light_dir_uniform.type = RDUniform.UNIFORM_TYPE_VEC3
light_dir_uniform.name = "light_direction"
light_dir_uniform.set_vec3_value(Vector3(-1, -1, -1).normalized())

var light_color_uniform = RDUniform.new()
light_color_uniform.type = RDUniform.UNIFORM_TYPE_VEC3
light_color_uniform.name = "light_color"
light_color_uniform.set_vec3_value(Color(1, 1, 1))  // White light

RenderingDevice.shader_set_uniforms(shader_id, [light_dir_uniform, light_color_uniform])

Animating Properties Over Time

For more dynamic scenes, you can animate shader properties over time. Let’s create a uniform that will control the offset of a wave effect in a vertex shader:

var wave_offset_uniform = RDUniform.new()
wave_offset_uniform.type = RDUniform.UNIFORM_TYPE_VEC2
wave_offset_uniform.name = "wave_offset"
wave_offset_uniform.set_vec2_value(Vector2())

func _process(delta):
    var wave_offset = wave_offset_uniform.get_vec2_value()
    wave_offset.x += delta * 0.1  // Increase wave X-offset over time
    wave_offset.y += delta * 0.2  // Increase wave Y-offset over time
    wave_offset_uniform.set_vec2_value(wave_offset)
    
    RenderingDevice.shader_set_uniforms(shader_id, [wave_offset_uniform])

By gradually changing the `wave_offset` in the `_process` function, the wave effect on our shader will appear to animate over time.

Customizing Material Properties

Let’s say you want to adjust the specular highlight of a material in response to gameplay, such as making an item flash when it is interactable:

var specular_intensity_uniform = RDUniform.new()
specular_intensity_uniform.type = RDUniform.UNIFORM_TYPE_FLOAT
specular_intensity_uniform.name = "specular_intensity"
specular_intensity_uniform.set_float_value(1.0)

func make_item_flash():
    var target_intensity = 2.0  // Target intensity for flashing effect
    var current_intensity = specular_intensity_uniform.get_float_value()
    current_intensity = lerp(current_intensity, target_intensity, 0.1)
    specular_intensity_uniform.set_float_value(current_intensity)
    
    RenderingDevice.shader_set_uniforms(shader_id, [specular_intensity_uniform])

The `lerp` function smoothly interpolates between the current intensity and the target intensity, creating a flashing effect when called, for example, within the `_process` or `_physics_process` functions.

Using Texture Masks

Shaders can also use texture masks to create interesting effects, such as revealing or hiding parts of a sprite. Here’s how you might pass a mask texture to your shader:

var mask_texture_uniform = RDUniform.new()
mask_texture_uniform.type = RDUniform.UNIFORM_TYPE_SAMPLER
mask_texture_uniform.name = "mask_texture"
// Assume 'mask_texture' is a previously loaded black and white mask texture
mask_texture_uniform.set_texture_value(mask_texture)

RenderingDevice.shader_set_uniforms(shader_id, [mask_texture_uniform])

In this way, the shader can use the mask texture to determine which areas of the sprite should be visible and which should be transparent, based on the grayscale values of the mask.

These examples illustrate the diversity and power of RDUniform within the Godot 4 engine. Through RDUniforms, you can manipulate nearly every aspect of visual rendering, achieving highly dynamic and interactive graphics. Keep experimenting with different uniform types and values to see just how much you can push the graphical boundaries of your game.

Where to go next with Godot 4

Embracing the fundamentals of RDUniform and shader programming in Godot 4 is just the beginning of your game development journey. To continue building upon what you’ve learned and to dive deeper into the world of game creation, we invite you to explore our Godot Game Development Mini-Degree. This carefully structured program will guide you through the intricacies of the Godot 4 engine and help you master the art of making cross-platform games. Filled with various topics ranging from 2D and 3D game mechanics to advanced programming concepts, this Mini-Degree is perfect whether you’re a novice or an experienced developer eager to fine-tune your skills.

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Conclusion

As we’ve delved into the depths of the RDUniform class in Godot 4, it’s clear that mastering uniforms is a significant step toward creating visually striking and high-performance games. The power and flexibility provided by these data structures are unparalleled, and with the knowledge you’ve acquired from this tutorial, you’re well-equipped to manipulate rendering to your every whim. But remember, the journey of learning and discovery is continuous, filled with endless opportunities to sharpen your skills and expand your creative horizons.

We at Zenva encourage you to leap further into this journey by exploring our comprehensive Godot Game Development Mini-Degree. It’s time to turn your curiosity into creation, your ideas into reality, and join a thriving community of developers who share your passion. Harness the full potential of Godot 4 and make your mark in the world of game development. Let’s bring your dreams to life, one line of code at a time!

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