Smooth Edges

Learn to create smooth edge transition effects using the smoothstep function, contrasting with the hard edges of the step function.

Overview

• Use a distance field and a mask to shape the image.

Learning Objectives

• Understand the three parameters of the smoothstep() function and their roles.
• Learn how to use smoothstep() to create a smooth transition between two values.
• Compare the effect differences between smoothstep() and step() in edge processing.
• Master applying smoothstep() to shape edges to achieve anti-aliasing or softening effects.

Prerequisites

• simple-circle
• step-function-mask

Inputs

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

Key Concepts

• Distance to center builds a distance field.

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

• Convert distance into a mask.

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

How To Implement (Step-by-step)

• Center coordinates: p = vUv - 0.5.
• Compute distance: d = length(p).
• Build a mask with smoothstep or step.
• Mix foreground/background by the mask.

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().