如何绘制一个球体

 DgnModel dgnModel = Session.Instance.GetActiveDgnModel();
            DgnSphere sphereData = new DgnSphere(DPoint3d.Zero, 1000);
            Element sphereElem = DraftingElementSchema.ToElement(dgnModel, sphereData, null);
            sphereElem.AddToModel();

 DgnModel dgnModel = Session.Instance.GetActiveDgnModel();
            DgnSphere sphereData = new DgnSphere(DPoint3d.Zero, 1000);
            Element sphereElem = DraftingElementSchema.ToElement(dgnModel, sphereData, null);
            sphereElem.AddToModel();