McNeel Wiki

public static Rhino.Commands.Result AddCylinder(Rhino.RhinoDoc doc)
{
  Rhino.Geometry.Point3d center_point = new Rhino.Geometry.Point3d(0, 0, 0);
  Rhino.Geometry.Point3d height_point = new Rhino.Geometry.Point3d(0, 0, 10);
  Rhino.Geometry.Vector3d zaxis = height_point - center_point;
  Rhino.Geometry.Plane plane = new Rhino.Geometry.Plane(center_point, zaxis);
  const double radius = 5;
  Rhino.Geometry.Circle circle = new Rhino.Geometry.Circle(plane, radius);
  Rhino.Geometry.Cylinder cylinder = new Rhino.Geometry.Cylinder(circle, zaxis.Length);
  Rhino.Geometry.Brep brep = cylinder.ToBrep(true, true);
  if (brep != null)
  {
    doc.Objects.AddBrep(brep);
    doc.Views.Redraw();
  }
  return Rhino.Commands.Result.Success;
}

Public Shared Function AddCylinder(ByVal doc As Rhino.RhinoDoc) As Rhino.Commands.Result
  Dim center_point As New Rhino.Geometry.Point3d(0, 0, 0)
  Dim height_point As New Rhino.Geometry.Point3d(0, 0, 10)
  Dim zaxis As Rhino.Geometry.Vector3d = height_point - center_point
  Dim plane As New Rhino.Geometry.Plane(center_point, zaxis)
  Const radius As Double = 5
  Dim circle As New Rhino.Geometry.Circle(plane, radius)
  Dim cylinder As New Rhino.Geometry.Cylinder(circle, zaxis.Length)
  Dim brep As Rhino.Geometry.Brep = cylinder.ToBrep(True, True)
  If brep IsNot Nothing Then
    doc.Objects.AddBrep(brep)
    doc.Views.Redraw()
  End If
  Return Rhino.Commands.Result.Success
End Function

import Rhino
import scriptcontext
import System.Guid
 
def AddCylinder():
    center_point = Rhino.Geometry.Point3d(0, 0, 0)
    height_point = Rhino.Geometry.Point3d(0, 0, 10)
    zaxis = height_point-center_point
    plane = Rhino.Geometry.Plane(center_point, zaxis)
    radius = 5
    circle = Rhino.Geometry.Circle(plane, radius)
    cylinder = Rhino.Geometry.Cylinder(circle, zaxis.Length)
    brep = cylinder.ToBrep(True, True)
    if brep:
        if scriptcontext.doc.Objects.AddBrep(brep)!=System.Guid.Empty:
            scriptcontext.doc.Views.Redraw()
            return Rhino.Commands.Result.Success
    return Rhino.Commands.Result.Failure
 
if __name__=="__main__":
    AddCylinder()