Parallax is the apparent shift in an object's position when it is seen from two different angles. In stereo vision, that shift is measured between two cameras to estimate depth: objects that move more across the image pair are usually closer, while distant objects shift less. This geometric cue is useful because it turns ordinary images into spatial measurements.
In cyber security, parallax matters wherever cameras are used for authentication, surveillance, or inspection. Depth-aware systems can help detect spoofing, such as a flat photo or replayed video presented to a face-recognition camera, because a real 3D subject produces consistent parallax while a fake often does not. Attackers may also try to confuse vision systems by changing angle, distance, lighting, or motion, so defenders rely on calibration, synchronization, and multiple viewpoints to keep measurements trustworthy. In short, parallax is a basic physical signal that many security systems use to tell real scenes from deceptive ones.