Perspective · 7 of 8 · 6 min

Where the lines already agree

You do not place a vanishing point and then force the drawing. You extend edges that are parallel in the world, and the point is where they meet.

1
Pick a parallel pair
Both sides of the ceiling. Both curbs. Both top edges of a cornice. They must be parallel in space, not merely both diagonal on the page.
2
Extend them
The meeting point is the vanishing point. For horizontal edges it must land on eye level. A third edge that misses the point was not really parallel.
3
Two points, still one horizon
On a corner, the left set and the right set each have a point. Those two points share a height. If your two guesses do not, one of them is off eye level.

Critique

Drill

The floor lines are parallel in the room. Tap where they meet. Eye level is already drawn.