Noise Functions

Learn and implement common noise functions in GLSL, such as random noise, value noise, and gradient noise (like a simplified version of Perlin noise), used for generating various procedural textures and effects.

Overview

• Generate procedural noise and map it to color.

Learning Objectives

• Understand the basic principles and characteristics of different types of noise (random noise, value noise, gradient noise).
• Learn how to implement a simple pseudo-random number generator in GLSL.
• Master the implementation of value noise, including lattice points and interpolation.
• Gain an initial understanding of the concept and implementation ideas of gradient noise (like Perlin noise).
• Be able to use the learned noise functions to generate simple procedural textures.

Prerequisites

• glsl-data-types
• glsl-functions
• vector-operations

Inputs

• vec2 u_resolution — Canvas size in pixels.
• float u_time — Time in seconds.

Key Concepts

• Noise is built from random values on a grid plus smooth interpolation.

vec2 i = floor(p);
vec2 f = fract(p);
vec2 u = f*f*(3.0-2.0*f);
float n = mix(mix(a,b,u.x), mix(c,d,u.x), u.y);

• Map noise to color with mix or thresholds.

vec3 color = mix(colorA, colorB, n);

How To Implement (Step-by-step)

• Scale UV to control frequency (e.g. p = vUv * 6.0).
• Compute base noise (hash/valueNoise).
• Optionally sum octaves (FBM) for detail.
• Map noise to grayscale or color.

Self-check

• Does it compile without errors?
• Does the output match the goal?
• Are key values kept in [0,1]?

Common Mistakes

• Clamp t into [0,1] when needed.
• Don’t use raw pixels without normalization.
• Make sure edge0 < edge1 for smoothstep().
• Change frequency by scaling before fract().