To set points on a line perpendicular to the picture plane we can use co-planar straight lines that form an angle of 45° with the picture plane.

These straight lines **m** intersect the straight line** r** that is perpendicular to the picture plane and the trace **tπ****1** of the plane to which it belongs, identifying equal segments. The perspectives **m’ **have their vanishing point **I’m** on the distance circle and on the vanishing line **i’π****1** of the plane to which they belong.