Drawing Circles

Learn how to draw a basic circle using distance functions in GLSL.

Learning Objectives

- Understand distance-based shape rendering

- Learn to use the distance() function

- Practice creating smooth edges with smoothstep()

Key Concepts

Distance Function

Calculate distance from current pixel to circle center:

`glsl

float dist = distance(uv, center);

`

Circle Rendering

Create a circle by comparing distance to radius:

- Inside circle: dist < radius

- Outside circle: dist >= radius

Smooth Edges

Use smoothstep() for anti-aliased edges:

`glsl

float circle = 1.0 - smoothstep(radius - edge, radius + edge, dist);

`

Exercise

Draw a white circle on a black background, centered on the screen.

Hints

1. Center the UV coordinates: uv - 0.5

2. Choose an appropriate radius (try 0.3)

3. Use distance() to calculate pixel distance from center

4. Use step() or smoothstep() to create the circle

Expected Result

You should see a clean white circle centered on a black background.