Fillet

Fillet rounds sharp edges. It is topology-sensitive: selected edges are stored as kernel references with lineage so the feature can survive many upstream edits.

Constant radius

The common case is a constant radius over one or more edges. Select edges in the viewport, open Fillet, enter a radius, and add the feature. The radius can be a literal value or a formula-backed value in the IR.

Variable radius

The IR supports per-edge radius overrides and sampled radii along an edge. Kernels linearly interpolate sampled variable-radius data in the first implementation. Use this when a grip, ergonomic transition, or moulded surface needs a changing round instead of one fixed radius.

Full-round

A full-round fillet uses three faces: left, centre, and right. The centre face is rounded away into a smooth bridge between the side faces. This is useful on ribs and tabs where a semicircular crown is the design intent.

Selection

Fillet and chamfer require edge selections. If the button is not visible in the modifier row, select one or more edges first. If an edge selection breaks after a major topology change, reselect the intended edge and update the feature.