Cool, I did spend some time trying to figure out perspective too, especially if you're at different distances and eye levels for an object. What I did in the end was to draw two rectangles. A larger rectangle in front, and a smaller rectangle at the back, at any position. You can play around with the size and positions of the rectangles and connect them to see how you instinctively identify the perspective there.

^ With that I can basically extrapolate how an object looks in its 3d space.

Maybe the rectangles (extrapolated into cuboids) would be useful for you? There is both the back-to-front and below-to-above aspect you have to deal with. I could poke you on telegram to show you what I mean if you'd like :3

Yes, I'm interested, sorry, I just can't check FA at my new job (it's blocked because "contains porn therefore it will hijack our computers") and when Saturday came...I forgot