Build NURBS Curve

Dependencies

This node can optionally use Geomdl library; also it can optionally use FreeCAD libraries.

Functionality

This node generates a NURBS Curve object, given all it’s details: control points, weights and knot vector.

Inputs

This node has the following inputs:

• ControlPoints. NURBS curve control points. This input is mandatory.

  

• Weights. NURBS curve control point weights. If this input is not linked, it will be assumed that all control points have weight of 1. This input is not available when Curve mode parameter is set to BSpline.

  

• Knots. NURBS curve knot vector. This input is not available if Knots parameter is set to Auto.

  

• Degree. NURBS curve degree. The default value is 3.

  

Parameters

This node has the following parameters:

• Implementation. This defines the implementation of NURBS mathematics to be used. The available options are:

  

  • Geomdl. Use Geomdl library. This option is available only when Geomdl package is installed.

  • Sverchok. Use built-in Sverchok implementation.

  • FreCAD. Use FreeCAD libraries. This option is available only when FreeCAD libraries are installed.

  In general, built-in implementation should be faster; but Geomdl implementation is better tested. The default option is Geomdl, when it is available; otherwise, built-in implementation is used.

• Curve mode. This defines the type of curve to be built:

  

  • NURBS: rational B-Spline curve (with ability to have different weights of control points)

  • BSpline: non-rational B-Spline curve (all control points have equal weight)

  The default option is NURBS.

• Knots. This defines how the knot vector is specified:

  

  • Auto: Knot vector is generated automatically (the curve will be clamped and periodic).

  • Explicit: Knot vector is explicitly defined in the Knots input of the node.

  The default option is Auto.

• Normalize knots. If checked, all knotvector values will be rescaled to [0 .. 1] range; so, the curve domain will always be from 0 to 1. If not checked, the curve domain will be defined by knotvector.

  

• Cyclic. Whether the curve should be cyclic (closed). This option is available only when the Knots parameter is set to Auto. Unchecked by default.

  

Outputs

This node has the following outputs:

• Curve. The generated NURBS curve object.

• Knots. NURBS curve knotvector.

  

Example of usage

• Curves-> Evaluate Curve

• Number-> List Input

• Vector-> Vector sort

• Text-> Stethoscope

• Viz-> Viewer Draw

• Scene-> Objects In Lite

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Updated example:

• Number-> List Input

• Vector-> Vector sort

• Viz-> Viewer Draw Curve

• Scene-> Get Objects Data