Ok so I am trying to introduce myself into some amateur mechanical drawing of biplanes and gliders. My problem is that I don't want to take guesses at how the foreshortening should be, I'd rather be as accurate as possible. I am not sure if this is a simple Trig question or possibly calculus. So obviously it's easy to draw something from the direct 90' angle of anything either the side or directly above, but I want to understand the "shrinking" proportions of when something is turned at an odd'ish angle. In the drawing I have circled in red the ends of the wing and put lines on the side of the wing where it slightly shrinks from direct parallel angles. So what I'd like to know is what the proportion is the wing tip furthest shrinks from the wing tip "closest" to the viewer in regards to a line, then I would like to know at the degree the parallel lines cease to be parallel and seem to become closer at the farther wing tip that make up the wing. Then after that I'd like to know what degree the tip closest points down with relation to the farther one pointing slightly up. I may not have explained it well enough so obviously let me know.