Curves Workbench¶
In one sentence: The Curves workbench (CurvesWB) is a FreeCAD addon dedicated to advanced NURBS curve and surface operations — blending, trimming, Gordon surfaces, sweep-on-surface, surface analysis, and more — complementing the Surface workbench for complex free-form modelling.
What is the Curves workbench for?¶
The Curves workbench extends FreeCAD's curve and surface capabilities beyond what the built-in Surface workbench provides. It focuses on:
- Advanced curve construction — parametric line, curve extension, joining multiple edges into a single B-spline, splitting curves, B-spline interpolation and approximation.
- Surface construction — Gordon surface (from a curve network), blend surface between two edges, sweep on surface, multi-loft, pipeshell sweeps, rotation sweep.
- Surface modification — flatten conical/cylindrical faces, trim faces with projected curves, segment surfaces along iso-parameter lines, truncate/extend.
- Analysis — zebra stripe continuity check, comb plot (curvature display), draft angle analysis, surface curvature analysis, reflect lines, waterline curves.
- Utilities — sketch on surface (map a sketch to a curved face), map objects on a face, extract geometry, convert to console script.
The Curves workbench is an external addon — it is not included in the FreeCAD installer. Install it via the Addon Manager (Tools → Addon Manager).
Installation¶
- Go to Tools → Addon Manager.
- Search for Curves.
- Click Install.
- Restart FreeCAD.
- The Curves workbench appears in the workbench selector.
NURBS concepts used in this workbench¶
| Concept | Description |
|---|---|
| B-spline | Piecewise polynomial curve defined by control points and knots |
| NURBS | Non-Uniform Rational B-Spline — B-spline with rational weights; can represent conics exactly |
| Iso-curve | A curve on a surface at constant U or V parameter |
| Gordon surface | A surface that exactly interpolates a network of crossing curves |
| Blend surface | A surface connecting two edges with a specified continuity (G0, G1, G2) |
| G0 / G1 / G2 continuity | Position / tangent / curvature continuity at a junction |
| Zebra stripes | Black-and-white stripe pattern that reveals G0/G1 discontinuities visually |
| Comb plot | Spines perpendicular to a curve, proportional to curvature, visualising curvature variation |
| Draft angle | Angle between a face normal and the mould release direction |
Menu structure¶
The workbench adds three menus:
| Menu | Contents |
|---|---|
| Curves | Parametric Line, Gordon Profile, Mixed Curve, Extend Curve, Join Curves, Split Curve, Discretize, Approximate, Interpolate, Blend Curve, Comb Plot, Curve on Surface |
| Surfaces | Zebra Tool, Trim Face, IsoCurve, Sketch on Surface, Map on Face, Sweep 2 Rails, Profile Support, Profile Sketch, Pipeshell, Gordon Surface, Segment Surface, Comp Spring, Reflect Lines, Multi-Loft, Blend Surface, Blend Solid, Flatten Face, Rotation Sweep, Surface Analysis, Draft Analysis, Truncate/Extend, Waterline Curves |
| Misc. | Geometry Info, Extract Shapes, Parametric Solid, Paste SVG, To Console, Adjacent Faces, B-Spline to Console |
See also¶
- Curve Tools — all curve construction and modification tools
- Surface Tools — all surface construction and modification tools
- Analysis and Utilities — analysis, inspection, and utility tools
- Surface workbench — built-in NURBS tools