I’ve been drawing for years and have a pretty good understanding of perspective. I had a hard time finding the answer questions like: when is it really a cube instead of having one side longer than the other. Sure, I could eyeball it fairly well and that’s usually good enough. But sometimes I really wanted it to look right.

The answer finally came in a Project Gutenberg eBook named “The Theory and Practice of Perspective”, by George Adolphus Storey, which was originally written in 1910. It’s free to download and seems to have the answer to all perspective questions. Get it at www.gutenberg.org/files/20165/20165-h/20165-h.htm.