Lysretning

Lysretning is the direction from which light rays arrive at a point or surface. In optics and related fields, it is described by a direction vector or by angular coordinates (for example azimuth and elevation) relative to a chosen reference frame. The light direction, together with the surface normal, determines the angle of incidence, which influences how the surface is illuminated.

In terms of reflection, light direction interacts with the material's properties. Specular reflections occur when the light direction approaches the mirror-like direction, while diffuse reflection disperses light in many directions. The apparent brightness and shading of an object depend on the angle between the light direction and the surface normal, commonly expressed by the cosine of the incidence angle.

Measurement and representation: In experiments and design, the light direction can be specified with a unit vector L pointing toward the surface. The dot product L · n gives the cosine of the incidence angle. In practice, designers or photographers describe lysretning as key light, fill light, back light to shape a subject.

Applications: Architectural lighting, product photography, and stage design use deliberate lysretning to control mood, depth, and texture. In computer graphics and 3D rendering, the light direction is a fundamental input for shading calculations. In solar energy, aligning solar collectors with the sun’s lysretning over time maximizes energy capture.