When do I actually need three-point perspective?

The numbering confuses people because it sounds like a progression from simple to advanced. It is not. The number of vanishing points is a fact about the relationship between you and the object, not a technique you choose. Work out where you are standing and the number falls out of it.

Step by step

1. Establish the horizon line as your eye level, always.Whatever the construction, the horizon line is at the height of your eye. Everything above it you see the underside of; everything below it you see the top of. Get this wrong and no number of vanishing points will save the drawing.
2. Use one point when you are square-on to a flat face.Standing facing a wall, or looking straight down a corridor or a railway line. One set of edges runs away from you to a single point on the horizon; the other two sets stay truly horizontal and truly vertical. This is why one-point suits interiors and streets seen head-on.
3. Use two points when you can see a corner.Stand so that a building shows you two faces. Now two sets of horizontal edges recede, each to its own vanishing point on the horizon, and the verticals remain vertical because you are still looking level. This is the default for almost all architecture drawn from standing height.
4. Add the third point only when you tilt.Look up at a tower from its base and the vertical edges converge towards a point high in the sky. Look down from a rooftop and they converge towards a point far below the ground. The third vanishing point lies on a vertical line through the centre of your view, and it is what produces the dramatic worm's-eye and bird's-eye effect.
5. Place the third point a very long way out.Bringing it close produces a fish-eye exaggeration that reads as a cartoon. For a believable tall building the third point is usually well off the paper — think several sheet-widths away — and the convergence of the verticals is subtle.
6. Keep the two horizontal points wide apart as well.The same rule applies on the horizon. Vanishing points crowded onto the page produce the distorted look of a wide-angle lens held too close.
7. Check by asking which sets of parallel edges are not parallel to your picture plane.This is the actual rule underneath all of it. Any set of parallel lines that is parallel to the flat plane of your paper stays parallel in the drawing. Any set that runs away from that plane converges to a point. Count the sets that run away and you have the number of vanishing points.

Tips

• Photographs taken with the camera held level have two-point perspective. The moment you tilt the phone up to fit a building in, the verticals converge and you are looking at three-point.
• Architects usually draw two-point deliberately even for tall buildings, because converging verticals look unstable in a presentation drawing. Comic artists use three-point for exactly the same reason in reverse.
• There is no such thing as four-point perspective in the classical sense; the curvilinear five-point drawings you see are a different projection altogether, useful for very wide views.
• If you are drawing from observation rather than construction, you do not need to know the number at all — just measure the angles you actually see against a held-up pencil.

Common mistakes

• Treating three-point as more advanced and therefore better — Applying converging verticals to an object you are looking at levelly makes it look as though it is falling over. Use the construction the viewpoint actually calls for.
• Putting the horizon at the middle of the page by default — The horizon is your eye level, so it belongs where your eye actually is relative to the subject. Sitting down to draw a table puts the horizon near the tabletop, not halfway up the sheet.
• Letting the vanishing points sit inside the picture — A vanishing point inside the frame means you are looking edge-on down that set of lines, which is legitimate in one-point but produces violent distortion when it happens by accident.

Questions people ask