RESEARCH: 180 degree rule

The 180degree rule is a filming technique which is shot anywhere within a 180degree perimeter. If the camera passes over the imaginary axis connecting the two subjects, it is called crossing the line. The new shot, from the opposite side, is known as a reverse angle. If broken verisimilitude will not be created and it will disorient the viewer, and break the flow of the scene. Here is an annotated drawing of the 180degree rule which shows the rule of the technique.

Here is an example of the 180degree rule; it shows filming around the 180degree perimeter.