Creates a C1 cubic NURBS approximation of a helix or spiral. For a helix, you may have radius0 == radius1. For a spiral radius0 == radius0 produces a circle. Zero and negative radii are permissible.

Namespace: Rhino.Geometry
Assembly: RhinoCommon (in RhinoCommon.dll) Version: Rhino 6.0

C#

public static NurbsCurve CreateSpiral(
	Point3d axisStart,
	Vector3d axisDir,
	Point3d radiusPoint,
	double pitch,
	double turnCount,
	double radius0,
	double radius1
)

VB

Public Shared Function CreateSpiral ( 
	axisStart As Point3d,
	axisDir As Vector3d,
	radiusPoint As Point3d,
	pitch As Double,
	turnCount As Double,
	radius0 As Double,
	radius1 As Double
) As NurbsCurve

axisStart

Type: Rhino.Geometry.Point3d
Helix's axis starting point or center of spiral.

axisDir

Type: Rhino.Geometry.Vector3d
Helix's axis vector or normal to spiral's plane.

radiusPoint

Type: Rhino.Geometry.Point3d
Point used only to get a vector that is perpedicular to the axis. In particular, this vector must not be (anti)parallel to the axis vector.

pitch

Type: System.Double
The pitch, where a spiral has a pitch = 0, and pitch > 0 is the distance between the helix's "threads".

turnCount

Type: System.Double
The number of turns in spiral or helix. Positive values produce counter-clockwise orientation, negitive values produce clockwise orientation. Note, for a helix, turnCount * pitch = length of the helix's axis.

radius0

Type: System.Double
The starting radius.

radius1

Type: System.Double
The ending radius.

Type: NurbsCurve
NurbsCurve on success, null on failure.

Supported in: 6.0.16224.21491, 5D58w

NurbsCurve Class
CreateSpiral Overload
Rhino.Geometry Namespace