/ic/ - Artwork/Critique

Might as well ask here instead of making a new thread.

I know about 1, 2, and 3 point perspectives, but how do you determine where those vanishing points go? What's stopping you from arbitrarily moving them to different places on the page?

I think two of the points are supposed to be on the horizon, but what's stopping you from squishing them together or pushing them waaaaaay far apart? What about how far up or down the 3rd point is?