This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
76. The somewhat symmetrical figure formed by the vanishing traces of all the planes in the object, together with all vanishing points, HPP, and the vertical and horizontal projections of the station point, is called the Vanishing Point Diagram of the object.
77. Having found the complete vanishing point diagram of the house, the perspective projection may be drawn. VH1 may be chosen in accordance with the kind of a perspective projection it is desired to produce (§ 29). In order that all the roof lines may be visible, VH1 has been chosen far below VH. The resulting perspective is a somewhat exaggerated bird's-eye view.
The point ep will be found on VHl, vertically under the point e in the diagram. ap e p lies in the picture plane, and shows the true height of the vertical wall of the house. From ap and ep, the horizontal edges of the walls of the main house vanish to vab and vad.
The points dp, bp, mp, and op are found on the upper horizontal edges of the main walls, vertically under the points where HPP is crossed by visual rays drawn through the points d, b, m, and o in the diagram. Vertical lines from dP and bp complete the visible vertical edges of the main house.
In a similar manner the perspective of the vertical walls of the porch is obtained.
Each roof line vanishes to its respective vanishing point. apf vanishes at vaf. fpdp vanishes at vfd. These two lines intersect in the point,fp. The ridge of the main house passes through fp, vanishing at vab gp ep Vanishes at v8C, passing through the point 'c p', which has already been determined by the intersection of the two upper rear horizontal edges of the main walls. bpgp vanishes at vbg, completing the perspective of the main roof.
in the porch, hp kp vanishes at Vhk, passing through the point hp. already determined by the vertical walls of the porch. kplp passes through lP, and vanishes at vkl. From kp the ridge of the porch roof vanishes at vad. From mp, a line vanishing at vmn will intersect the ridge in the point np, and represent the intersection of the roof planes Q and N. The vanishing point for OPnp falls outside the limits of the plate. opmp may be connected with a line which, if the drawing is accurate, will converge towards both TN and TR, and, if produced, would meet them at their intersection.
78. While constructing the vanishing point diagram of an object, the student should constantly keep in mind the general statements made in the note under § 69.
Plate IV. should now be solved.