Building Procedural Grid Lines in GLSL: A Complete Learning Path

Shaders often look intimidating because a finished effect is presented all at once. The Grid Lines exercise is a perfect example. At first glance it appears to be one small shader, but underneath it introduces several fundamental GLSL concepts that are much easier to understand individually.

Instead of treating it as one lesson, we broke it down into five focused articles. Each one explains a single building block before combining everything into a complete procedural grid.

If you are following this series from the beginning, here is the recommended reading order.

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1. Understanding fract() in GLSL: The Function That Makes Patterns Repeat

Understanding fract() in GLSL: The Function That Makes Patterns Repeat

Everything begins with fract(). In this lesson, we explore how the function removes the whole number from a value while keeping only its decimal portion. Although that sounds simple, it is the foundation of repeating textures and procedural patterns throughout shader programming.

By the end of the article, you will understand why fract() is one of the most frequently used functions in GLSL.

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2. Why Multiplying UV Coordinates Changes Everything in GLSL

Why Multiplying UV Coordinates Changes Everything in GLSL

Once we understand fract(), the next question naturally follows.

Why do we write:

vUv * density

before calling fract()?

This lesson explains how scaling UV coordinates changes the number of repeated tiles across the screen. You will learn why increasing the density creates smaller and more frequent repetitions without changing the shader itself.

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3. Mastering step() in GLSL: Drawing Sharp Lines Instead of Smooth Gradients

Mastering step() in GLSL: Drawing Sharp Lines Instead of Smooth Gradients

Until this point, our repeated coordinates still looked like gradients.

In this article, we introduce the step() function, which converts smooth values into sharp transitions. Instead of producing another gradient, the shader suddenly begins drawing crisp vertical lines.

This lesson also introduces the idea of procedural masks, one of the most important concepts in shader programming.

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4. Building Your First Procedural Grid in GLSL

Building Your First Procedural Grid in GLSL

Once vertical lines are working, creating a grid becomes surprisingly simple.

By adding a second step() function that operates on the y coordinate, we combine vertical and horizontal lines into a complete procedural grid.

This lesson demonstrates how complex effects often come from combining several simple functions rather than writing complicated code.

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5. Why min() Matters in GLSL: Fixing Grid Intersections the Right Way

Why min() Matters in GLSL: Fixing Grid Intersections the Right Way

Our grid already looks correct, but one small mathematical issue remains.

At every intersection, two line masks overlap, producing values greater than we actually need.

In this final lesson, we use the min() function to keep the mask inside the proper range. Although the visual difference is subtle, it introduces an important programming habit that becomes increasingly valuable as shaders become more advanced.

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