Paths, sweeps, and lofts

Create exact bounded ruled lofts and line, circular-arc, or composite path sweeps.

Lofts and sweeps are exact OCCT features in 0.1. Their admitted grammar is intentionally narrower than a general-purpose surface modeler so each accepted case has explicit validation and volume checks.

Ruled solid loft

const lower = cad.sketch("lower", plane.xy(), (sketch) =>
  sketch.profile(
    sketch.rectangle("lower-outline", { width: mm(40), height: mm(30) }),
  ),
);

const upper = cad.sketch(
  "upper",
  plane.xy(vec3(mm(0), mm(0), mm(50))),
  (sketch) =>
    sketch.profile(
      sketch.rectangle("upper-outline", { width: mm(20), height: mm(15) }),
    ),
);

const loft = cad.loft("loft", [lower, upper], { ruled: true });

The current document grammar requires at least two distinct, ordered, hole-free profiles on compatible parallel principal planes. Interpolation is ruled; smooth, guided, open, and holed lofts remain future contracts.

Polyline path

const path = cad.polylinePath("path", [
  vec3(mm(0), mm(0), mm(0)),
  vec3(mm(20), mm(0), mm(0)),
  vec3(mm(20), mm(20), mm(0)),
]);

Paths are first-class nodes, not sketch profiles. The polyline must be open and simple; repeated points and redundant collinear vertices are rejected.

Three-point circular arc

const arc = cad.circularArcPath("bend", {
  start: vec3(mm(0), mm(0), mm(0)),
  through: vec3(mm(7.071), mm(2.929), mm(0)),
  end: vec3(mm(10), mm(10), mm(0)),
});

through lies on the desired arc. It is not a Bézier control point. The three points must define one conditioned arc below a full turn.

Composite line/arc route

const route = cad.compositePath("route", {
  start: vec3(mm(0), mm(0), mm(0)),
  segments: [
    { kind: "line", end: vec3(mm(5), mm(0), mm(0)) },
    {
      kind: "circularArc",
      through: vec3(mm(8.535), mm(1.465), mm(0)),
      end: vec3(mm(10), mm(5), mm(0)),
    },
    { kind: "line", end: vec3(mm(10), mm(10), mm(0)) },
  ],
});

A composite has at least two segments and at least one arc. Segments connect by construction because each begins at the previous end. Arc junctions must be forward G1 tangent; line-line junctions use right-corner semantics.

Sweep a profile

The profile plane must be seated at the path start with its normal parallel to the initial tangent:

const section = cad.sketch("section", plane.yz(), (sketch) =>
  sketch.profile(
    sketch.rectangle("section-outline", { width: mm(2), height: mm(2) }),
  ),
);

const swept = cad.sweep("swept", section, route, {
  frame: "corrected-frenet",
  transition: "right-corner",
});

Those option values are currently the only admitted frame and transition contracts; omitting them selects the same defaults.

Clearance and conditioning

InvariantCAD validates more than path syntax. It checks the full profile envelope against arc radius, remote path returns, adjacent curvature neighborhoods, native transfer floors, and numerical conditioning. Composite results are checked against an analytic transported-centroid volume oracle.

The important user-facing rule is simple: the complete cross-section needs physical clearance around every bend and between remote path segments. Shrinking only a nominal width while leaving an off-center profile can still be invalid.

For exact tolerances, major-arc restrictions, centered-profile stock-runtime behavior, and the owned-facade refinements, read the complete guide.

Not yet supported

• closed or full-circle path documents
• Bézier, B-spline, and helix paths
• guided or variable-section sweeps
• arbitrary transition and frame modes
• holed sweep profiles
• general smooth surfacing

Rejected input receives a structured diagnostic; it is not silently approximated with a different feature.