# SubDFriendlyKnotType enum

Namespace: [Rhino.Geometry](https://developer.rhino3d.com/api/rhinocommon/namespace/rhino.geometry.md) · Assembly: [RhinoCommon](https://developer.rhino3d.com/api/rhinocommon/assembly/rhinocommon.md)

```cs
public enum SubDFriendlyKnotType
```

ON_SubD::SubDFriendlyKnotType identifies the types of subd friendly NURBS knot vectors. SubD friendly NURBS curves and surfacaes are always cubic and nonrational. Any time there is a multiple knot, the 2nd derivative is zero at the corresponding parameter. SubD friendly NURBS curves are either periodic or have zero 2nd derivative at the ends.

## Values

| Name | Value | Description |
| --- | --- | --- |
| Unset | 0 | Not a valid type. Used to indicate the type has not been set and to encourage developers to explicitly specify a type. |
| UnclampedUniform | 1 | NURBS knot vector is an unclamped uniform cubic knot vector. Every knot interval has the same length. Every knot has multiplicity 1. |
| ClampedUniform | 2 | NURBS knot vector is a clamped uniform cubic knot vector. Every interior knot interval has the same length. End knots have multiplicity 3 and interior knots have multiplicity 1. |
| ClampedPiecewiseUniform | 4 | NURBS knot vector is a clamped piecewise uniform cubic knot vector. All nonzero knot intervals have the same length. End knots have multiplicity 3 and interior knots have multiplicity 1 or 3. Interior knots with multiplicity 3 correspond to interior SubD creases. |
| Unfriendly | 127 | NURBS knot vector is not subd friendly. |