godot noise in shader function function not found

Lussy04

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24-01-2025

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Are you experiencing the frustrating "Shader Function Not Found" error in your Godot shaders when trying to use noise functions? This common issue arises when Godot's shader language (GLSL) can't locate the noise function you're calling. This article will guide you through troubleshooting and resolving this problem, allowing you to seamlessly integrate noise functions into your shaders.

Understanding the Problem

The "Shader Function Not Found" error usually means your shader code is attempting to use a function that isn't defined or isn't accessible within the shader's scope. With noise functions, this often occurs because:

• Incorrect function name: You might have misspelled the function name (e.g., noise instead of noise1, or a slight variation).
• Missing include: Some noise functions might require including specific header files or libraries. Godot's shader language doesn't automatically include everything.
• Incorrect shader language version: Older versions of GLSL might lack certain noise functions available in newer versions.

Common Noise Functions and Their Implementation

Let's explore some frequently used noise functions and how to correctly implement them in your Godot shaders.

1. noise() (Built-in)

Godot's built-in noise() function is readily available and requires no extra includes. However, it's crucial to remember its signature: it expects a vec3 (three-dimensional vector) as input. This vector represents the coordinate in 3D space where you want to sample the noise. The output is a scalar value between 0 and 1.

vec3 uv = vec3(UV, 0.0); //Assuming you're using UV coordinates
float noiseValue = noise(uv);

2. texture() (for Noise Textures)

If you're using a pre-generated noise texture, you can sample it using the texture() function. This eliminates the need for built-in noise functions within the shader itself. Make sure the texture is properly loaded and accessible.

uniform sampler2D noiseTexture;
vec4 noiseColor = texture(noiseTexture, UV);

3. Custom Noise Functions

You can also define your own noise functions within the shader, but this requires a deeper understanding of noise generation algorithms (like Perlin or Simplex noise). Defining your own gives you more control but adds complexity.

Troubleshooting Steps

1. Double-Check Spelling: Carefully review the name of your noise function. Even a single typo can cause the error.
2. Check Shader Language Version: Ensure your shader is using a compatible GLSL version that supports the noise function. Godot's shader editor usually indicates the version.
3. Verify Includes: Some advanced noise functions might need specific headers. For Godot, you typically won't need additional includes for basic functions like noise().
4. Scope: Ensure the function is called within the correct scope (e.g., within the fragment function).
5. Type Mismatches: Make sure the data types you're passing to the noise function match its expected input types (typically a vec2 or vec3). Incorrect types will lead to compiler errors.
6. Clean and Rebuild: Sometimes, Godot's shader compiler might cache old versions of your shader. Cleaning the project and rebuilding it can resolve this.
7. Simple Test: Create a minimal shader that only uses the noise function to isolate the problem. This helps determine if the issue lies with the noise function itself or other parts of your shader.

Example Shader with Noise

Here's a simple Godot shader demonstrating the use of the built-in noise() function:

shader_type spatial;
uniform vec4 albedo : hint_color = vec4(1.0);
uniform float noiseScale : hint_range(0.01, 10.0) = 1.0;

void fragment() {
    vec3 uv = vec3(UV, 0.0);
    float noiseValue = noise(uv * noiseScale); //Scale the noise
    ALBEDO = albedo * vec4(vec3(noiseValue), 1.0);
}

This shader applies a grayscale noise pattern based on the noise() function. Adjust noiseScale to control the frequency of the noise.

By carefully following these steps and understanding the nuances of noise function implementation in Godot's shader language, you can effectively overcome the "Shader Function Not Found" error and unlock the potential of noise for creating visually interesting effects in your games. Remember to consult the official Godot documentation for the most up-to-date information on shader functions and their usage.