aw vertical x y, cutting d b in v. Join at, cy; and these lines are the sides of the gable. If the length of the roof A A/ is also given, draw in perspective the complete parallel opiped a' d' b c, and from y draw y y' to the vanishing-point of A a', cutting 1/ b' in y'. Join a' y, and you have the…
Perspective
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.