Checking smoothness

A product looks premium when light glides over it without a break: no visible seams where a handle meets the body, no flat spots, no sudden jumps in the reflection. The smoothness check makes that visible.

Open it with ⌘K → Check smoothness, from the context ring on a sculpted or flowing shape, or from the Recipe's ⋯ → Check smoothness. A card appears at the side of the view; close it with ✕ (or run the command again).

Reflection stripes

The shape reflects a studio of long, parallel light tubes. Read the stripes like this:

• Stripes flow through a join smoothly → the surfaces meet seamlessly (the premium look).
• Stripes bend sharply at a line → the surfaces meet without an edge, but the reflection jumps there. You'll see it on a rounded edge next to a flat face.
• Stripes break (they don't line up) → there's a visible crease.

Change the number of Stripes (more stripes = finer detail) and their Direction (across, up, diagonal), and orbit around: the stripes are fixed to your view, so they slide over the surface as you turn it — creases stay put and stand out.

The stripes also work while you sculpt: leave the check open and enter Sculpt mode, and the stripes follow the shape as you drag.

Curvature colours

Switch to Curvature to colour the surface by how tightly it curves:

• Green — flat.
• Amber → red — curving outward, more and more tightly (red spots are tight corners or bumps).
• Cyan → blue — curving inward (hollows, saddles).

Smooth shapes show gentle gradients; abrupt colour changes show where the curvature jumps.

Findings and "Smooth it"

Under the stripes, a one-line verdict ("Smooth everywhere", "12 visible creases", "No creases left") and the findings in plain words:

• Visible crease — sharp edges where faces meet at an angle.
• Reflections jump — a smooth join that isn't seamless (a rounded face meeting a flat one).

Click a finding to fly the camera there; its edges light up in coral. Smooth it adds a Smooth blend step on those edges — a seamless, softer-than-fillet transition — through the normal Recipe, so ⌘Z undoes it and you can change its size in the Recipe like any other value. Smooth all blends every crease at once. You can also select edges yourself and use ⌘K → Smooth blend, or right-click an edge of an organic shape.

When the blend has to be a regular rounding

On some edges a curvature-smooth blend can't be built — for example all the edges of a box, a loop of edges that turns sharp corners, or a closed loop all the way around a post. There the blend step keeps a regular rounding instead and says so in the Recipe ("The curvature-smooth blend couldn't be built here, so a regular rounding was used instead."), and the message after Smooth it says Added a regular rounding.

The check accepts that rounding: its edges aren't listed as places where reflections jump, and there's no Smooth it on them, because another blend can't do better. The verdict reads No creases left (or the creases still left elsewhere), with one line under it: These edges keep a regular rounding: a curvature-smooth blend can't be built there, so there's nothing more to smooth.

If a rounding meets itself at a sharp corner (a loop of edges rounded on its own), that corner stays a visible crease without Smooth it: round the edges that run into the corner too, and it softens.

A sharp edge isn't always a mistake: a crisp parting line or a flat base on purpose is fine. The check shows where they are, you decide.

For CAD users: stripes are zebra analysis; a break is a G0 (position-only) join, a kink G1 (tangent), flowing stripes G2 (curvature-continuous). The curvature colours show mean curvature. Pro terms shows these names in the app.