There's something I don't understand about vanishing point art (with respects to using one, two, three, four, etc. vanishing points): which one is correct (in the sense that it matches human perception, or a photograph)? Or are they equivalent?

Quote Originally Posted by Replicon View Post
Xei is right about the angle.

Though really, distances (as well as sheer sizes) are LINEAR, not exponential. Otherwise, if you stood on parallel railroad tracks, they wouldn't look like two straight lines heading into the horizon (meeting at infinite distance), but two curved lines, due to the exponentialness. But for the reason Xei showed, as an object gets closer (say the train on the tracks ), the angle from its left to right (or top to bottom, etc.) increases and it appears to grow faster. If I remember right, the size of an object is inversely proportional to the distance (size = (some constant) * (actual size) / (distance from observer)), which if course, is not a straight line, and shoots up as distance goes to wards zero.
When you say size here, I suppose you are comparing the object to some standard (such as a metre stick one metre away), as opposed to the absolute measure of angle?