I am trying to work out how to draw consistently sized cubes when I have multiple three-point perspective systems. I have a cube in one system and I want to draw an identically sized cube in another system. For example, one cube may be facing up and to the left and the other will be flipped to face a different angle. I would like to be able to translate the cube from one perspective to another without any guess work. How can I do this?
In the following image the red and blue cubes are in the perspective system with VPs 1 and the green, black and purple cube is in the system with VPs numbered 2. The circle is the 90 degree cone of vision and the horizontal line is the horizon line. The 45s are 45 degree vanishing points.
I would like a method to allow me to render a cube in perspective 2 that is the same size as a cube I rendered in perspective 1 without guessing the length of a side.
This requires understanding of two actions
1) building exact cube in the same VP system (Loomis "Successful Drawing")
2) applying up to three local rotations to the cube, to get the cube with needed VP system.
Action 1) may be used first if you want to place a cube in more convenient position before rotating it.
You have an initial cube, then you make up to three local rotations of it(Top rotation - moving to side VPs on horizon, Side rotation - moving up/down horizon line, top/bottom VP, Front rotation- rotating horizon line, top/bottom VP).
From new cube you get new vanishing points, then you project result cube using Loomis perspective rules.
To the contrary, Walt Stanchfield in "Gesture Drawing for Animation" gives explanation of perspective that was used by Bruce McIntyre to teach young kids. It's pretty easy and may save time in work.
The guide you found is probably one of the best sources on the web. It is very technical but take it slowly and it will make sense. The techniques work too.
I was going to point you his way for what you're talking about. One thing to note is that your first set of cubes are actually in two point, just two-point that is rotated 90 degrees. Only your last cube is in three.