The 180° Line: Documentary Camera Blocking

Shot Camera

Angle around subjects 45°

Distance 6.0 m

Height 1.8 m

Coverage Presets

Continuity Status

✓ Line-safe — Side A

Perp. distance from line

2.0 m

Camera angle

45.0°

Monitor screen order

A left · B right

How it works

Draw an imaginary line — the axis of action — through the two subjects of a scene. The 180° rule says: once a shot establishes which side of that line the camera is on, every following shot in the same scene should stay on that same side. Crossing it flips the two subjects' left/right positions on screen, which reads to a viewer as a jarring, disorienting jump — exactly the continuity error documentary editors are trained to avoid when cutting between an interviewer's coverage shot and reaction cutaways.

Line direction:  d = B − A  (A, B = subject positions)
Side of camera:  sign( d.x·(P−A).z − d.z·(P−A).x )
Screen order:    transform A, B into camera space;
                  compare local X — more negative X = screen-left

Angle / Distance / Height — reposition the shot camera freely in 3D around the two subjects.
Flip Across the Line — jumps 180° to the mirrored angle on the opposite side, so you can see the exact moment the monitor's left/right order reverses.
Coverage Presets — realistic documentary shot sizes (wide two-shot, medium, close-up) placed on the current safe side, showing how real coverage still respects one axis.
The small monitor is a second real camera rendering the same 3D scene — the reversal you see there is genuine perspective projection, not a scripted effect.

Real-world relevance: every multi-camera interview, verité scene and reality-TV two-shot in documentary filmmaking is blocked around this exact rule, so an editor can freely intercut coverage without confusing the audience about where people are relative to each other.

Director's Monitor

Subject A Subject B Shot camera

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The 180° Line: Documentary Camera Blocking Simulator