public void CreateSpline() { Point3d[] pt = new Point3d[4]; pt[0] = new Point3d(0, 0, 0); pt[1] = new Point3d(10, 0, 0); pt[2] = new Point3d(30, 20, 0); pt[3] = new Point3d(60, 50, 0); Point3dCollection pts = new Point3dCollection(pt); ObjectId splineId = ModelSpace.AddSpline(pts); }