Smooth Edges

step creates hard edges, but many effects need soft transitions. smoothstep interpolates smoothly between two thresholds.

What is smoothstep

smoothstep(edge0, edge1, x) transitions smoothly from 0 to 1 between edge0 and edge1:

• x <= edge0 → returns 0.0
• x >= edge1 → returns 1.0
• in between → smooth transition

• d < 0.2: mask = 1.0 (inside circle, white)
• d > 0.3: mask = 0.0 (outside circle, black)
• 0.2 < d < 0.3: soft edge

step vs smoothstep

step snaps at the boundary; smoothstep eases from edge0 to edge1. Transition width = edge1 - edge0 — narrower means harder edge.

Exercise

The exercise has mask = 0.0 (solid black). Use smoothstep(0.2, 0.3, d) to create a soft-edged circle mask.

Answer Breakdown

smoothstep(0.2, 0.3, d) starts rising at d = 0.2 and reaches 1.0 at d = 0.3. The 1.0 - inverts it: white at center, black outside.

Transition range is 0.3 - 0.2 = 0.1. Change 0.3 to 0.25 for a sharper edge; change it to 0.5 for a wider blur.