**Diagonals, mid-lines**

Fig. 1, left: The lines *a* and *b* presenting top and bottom of a
wall (*ABCD*) of even heights throughout, converge to a common Vanishing
Point (*VP1*) on the Horizontal Line (*HL*).

Fig. 1, right: Top- and bottom-lines of posts of equal heights and standing
in line converge to a single *VP2*.

Fig. 2, left: The diagonals of the plane define its mid-point *M*.

Fig. 2, right: drawing further diagonals allow to create lines marking equal intercepts.

Fig. 3: A perpendicular line to the Ground Plane (GP) through *M*
prepares the base to locate *D -* defining e.g. the end of the mid-line of
the roof.

Fig. 4, right: Draw line through* M* and *VP2* to create *N*, draw
line from *B* through *N* to create *Q*, draw vertical
through Q to create L. The resulting blue and yellow areas are of equal size, the distances
*AD* and *DQ* of equal length.

Figures 5 and 6: The sets of diagonals of areas of equal size converge to Vanishing Points (VP) located on a vertical line to the Horizontal Line (HL).