formula_14 is the center of the rectangle formula_332. The side formula_333 of the rectangle is divided into n equal spaced line segments and this division is projected parallel with the diagonal formula_334 as direction onto the line segment formula_335 and assign the division as shown in the diagram. The parallel projection together with the reverse of the orientation is part of the projective mapping between the pencils at formula_314 and formula_337 needed. The intersection points of any two related lines formula_338 and formula_339 are points of the uniquely defined ellipse. With help of the points formula_340 the points of the second quarter of the ellipse can be determined. Analogously one obtains the points of the lower half of the ellipse.