- Parallel lines in 3D space converge in images.
- The line of the horizon is formed by `infinitely' distant points (vanishing points).
- Any pair of parallel lines meet at a point on the horizon corresponding to their common direction.
- All `intersections at infinity' stay constant as the observer moves.

**The effects can be modelled mathematically using the `linear
perspective' or a `pin-hole camera'** (realized first by Leonardo?)

Subhashis Banerjee 2008-01-20