I made this free tool that lets you check the vanishing points of a cube and change its focal length. I had some useful realizations about perspective thanks to it, and I hope it helps you as well! I last worked on it a few months ago, and it's not as finished as I would make a complete product, but I figured this may help someone! :) - Hold left mouse click to orbit around the cube - Use mouse wheel to change focal length (it will change the camera's distance as well to keep the cube's apparent size). - Use on-screen controls to change the cube https://code-flame.itch.io/cube-buddy