Smoothstep Edge Fade

Use smoothstep() to achieve a fade transition at the edges of a shape, contrasting with step().

Overview

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

Learning Objectives

• Gain a deeper understanding of the application of smoothstep() in edge processing.
• Learn how to control the range and intensity of the fade by adjusting the parameters of smoothstep().
• Master creating graphical effects with soft edges.
• Be able to explain the main visual differences between smoothstep() and step().

Prerequisites

• smooth-edges
• step-function

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