incomingDirection

Incoming direction is a term used across science and engineering to denote the direction from which a signal, particle, or wave approaches a reference point or surface. It is usually described by a unit vector or by angular coordinates in a chosen coordinate frame. The concept is inherently relative, since the same physical situation can have different incoming directions depending on the reference surface or observer.

In optics, the incoming direction refers to the incident direction of light on a surface. The angle of incidence is the angle between the incoming direction and the surface normal, and it determines how light is reflected or refracted according to laws such as Snell's law. In acoustics and audio engineering, it describes the direction from which sound reaches a microphone or listener, informing beamforming and spatial sound rendering.

In computer graphics and rendering, the incoming direction commonly denotes the vector from a shading point toward a light source. It is a fundamental input for computing illumination, shading, and reflections, and is frequently represented as a normalized vector named something like incomingDirection in shading code.

In radar, sonar, and seismology, the incoming direction identifies where a received signal originated. Direction finding uses sensor arrays to estimate this vector, enabling localization or mapping of sources and events.

Representation often uses a unit vector, direction cosines, or spherical coordinates (azimuth and elevation). Proper use requires clear definition of the reference frame and whether the direction points toward or away from the surface or observer, as conventions vary across fields.