Find point on curve at distance

Demonstrates how find a point on a curve given a specified length from the start of the curve.

partial class Examples
{
public static Rhino.Commands.Result ArcLengthPoint(Rhino.RhinoDoc doc)
{
Rhino.DocObjects.ObjRef objref;
Rhino.Commands.Result rc = Rhino.Input.RhinoGet.GetOneObject("Select curve",
true, Rhino.DocObjects.ObjectType.Curve,out objref);
if(rc!= Rhino.Commands.Result.Success)
return rc;
Rhino.Geometry.Curve crv = objref.Curve();
if( crv==null )
return Rhino.Commands.Result.Failure;

double crv_length = crv.GetLength();
double length = 0;
rc = Rhino.Input.RhinoGet.GetNumber("Length from start", true, ref length, 0, crv_length);
if(rc!= Rhino.Commands.Result.Success)
return rc;

Rhino.Geometry.Point3d pt = crv.PointAtLength(length);
if (pt.IsValid)
{
doc.Views.Redraw();
}
return Rhino.Commands.Result.Success;
}
}

Partial Friend Class Examples
Public Shared Function ArcLengthPoint(ByVal doc As Rhino.RhinoDoc) As Rhino.Commands.Result
Dim objref As Rhino.DocObjects.ObjRef = Nothing
Dim rc As Rhino.Commands.Result = Rhino.Input.RhinoGet.GetOneObject("Select curve", True, Rhino.DocObjects.ObjectType.Curve,objref)
If rc IsNot Rhino.Commands.Result.Success Then
Return rc
End If
Dim crv As Rhino.Geometry.Curve = objref.Curve()
If crv Is Nothing Then
Return Rhino.Commands.Result.Failure
End If

Dim crv_length As Double = crv.GetLength()
Dim length As Double = 0
rc = Rhino.Input.RhinoGet.GetNumber("Length from start", True, length, 0, crv_length)
If rc IsNot Rhino.Commands.Result.Success Then
Return rc
End If

Dim pt As Rhino.Geometry.Point3d = crv.PointAtLength(length)
If pt.IsValid Then
doc.Views.Redraw()
End If
Return Rhino.Commands.Result.Success
End Function
End Class

import Rhino
import scriptcontext

def ArcLengthPoint():
rc, objref = Rhino.Input.RhinoGet.GetOneObject("Select curve", True, Rhino.DocObjects.ObjectType.Curve)
if rc!=Rhino.Commands.Result.Success: return rc
crv = objref.Curve()
if not crv: return Rhino.Commands.Result.Failure
crv_length = crv.GetLength()
length = 0
rc, length = Rhino.Input.RhinoGet.GetNumber("Length from start", True, length, 0, crv_length)
if rc!=Rhino.Commands.Result.Success: return rc
pt = crv.PointAtLength(length)
if pt.IsValid: