Interpolate NURBS Surface¶

Dependencies¶

This node can optionally use Geomdl and FreeCAD library to work.

Functionality¶

This node builds a NURBS Surface object, which goes through all specified points.

In fact, the generated curve always will be a non-rational curve, which means that all weights will be equal to 1.

To build a NURBS surface, one needs an array of M x N points (like “3 rows by 4 points”). There are two modes of providing this array supported:

You can provide a list of lists of points for each surface;
Or you can provide a flat list of points, and instruct the node to subdivide it into sublists of N points each.

Inputs¶

This node has the following inputs:

Vertices. Points to be interpolated. Depending on Input mode parameter, it expects either list of lists of control points per surface, or a flat list of control points per surface. This input is mandatory.
USize. This input is only available when Input mode parameter is set to Single list. The number of control points in a row. The default value is 5.
Degree U, Degree V. Available only when Geomdl or built-in Sverchok implementations used.

Degree of the surface along U and V directions, correspondingly. 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.
- FreeCAD. Use FreeCAD library. This option is available only when FreeCAD package is installed. The resulting surface is of degree 3 and continuity C2 (except we use 2x2 or 2xN grid of Vertices) .
In general (with large number of control points), 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.
Centripetal. This parameter is only available when Implementation parameter is set to Geomdl. Defines whether the node will use centripetal interpolation method. Unchecked by default.
Metric. This parameter is available only when Implementation parameter is set to Sverchok. This defines the metric used to calculate surface’s U, V parameter values corresponding to specified points. The available values are:
- Manhattan
- Euclidean
- Points (just number of points from the beginning)
- Chebyshev
- Centripetal (square root of Euclidean distance).
The default value is Euclidean.
Input mode. The available values are:
- Single list. The node expects a flat list of points for each surface. It will be subdivided into rows according to USize input value.
- Separate Lists. The node expects a list of lists of points for each surface.

Outputs¶

This node has the following outputs:

Surface. The generated NURBS surface.
ControlPoints. Control points of the generated NURBS surface.
KnotsU, KnotsV. Knot vectors of the generated NURBS surface.