Sweep Along Rail

Sweep a 2D profile along a 3D rail. At each rail point the profile is re-framed by a parallel-transport basis (tangent + normal + binormal), producing a smooth, non-twisting surface. A tube, a cable, a snake — any "extrusion along a non-straight path."

Node

Interactive preview is available in the interactive reader.

Sockets

profile (in): Path. Required — a 2D profile in its local XY plane (z is ignored).
rail (in): Path. Required — the 3D rail (≥2 points).
mesh (out): Mesh — the swept surface with optional caps.

Parameters

Cap start / Cap end: Close the first and last rings with a centroid fan. Defaults: on.
Closed profile: Whether the profile is a closed loop. Default: on.

How It Works

At every rail point we build an orthonormal frame via parallel transport — each frame is the previous frame rotated about the axis tangent_prev × tangent_next. This keeps the profile's orientation stable through curves, avoiding the flipping that pure Frenet frames suffer on straight segments.

The profile's local (x, y) maps to (binormal, normal) at each rail point, so a circle profile gives you a perfectly round tube.