Circle Outline

Draw a ring by using abs(distance - radius) and smoothstep().

Overview

• Draw a ring by measuring distance to a circle boundary.

Learning Objectives

• Compute distance to center
• Build a ring mask from abs(d-r)

Prerequisites

• simple-circle
• smooth-edges

Key Concepts

• Distance to center builds a distance field.

vec2 p = vUv - 0.5;
float d = length(p);

• Convert distance into a mask.

float ringDist = abs(d - r);
float mask = 1.0 - smoothstep(w, w + aa, ringDist);

How To Implement (Step-by-step)

• Compute distance d from center.
• Compute ring distance: abs(d - r).
• Convert ring distance to mask with smoothstep.
• Mix colors and output.

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.
• Make sure edge0 < edge1 for smoothstep().