Above is a rendering I made to help explain a basic way to categorize light sources. Lighting can be broken down into three fundamental geometric categories: point sources, linear sources, and planar sources.
Now, we don’t live in a conceptually perfect Euclidean world, and the perception of relative scale of course matters in how one defines a certain light source. What is approximating a skinny “line” of light at a far distance resembles a rectangular plane of light at a near distance, so context is essential in these categorizations.
A direct result of this relative scale perception issue is that when points, lines and planes are aggregated together in clusters, they create visual textures across a meta surface. Let’s call these the “3+1” fundamental geometries of lighting.