Directional sources are described by a direction alone, and are useful for modeling light sources that are effectively infinitely far away from the objects they illuminate. The direction need not be normalized. Point sources are defined as a single point in space. They produce shadows with sharp edges and are a good replacement for extended and other computationally expensive light source. Place a point light source with the given intensity at the given position.
Spotlights are useful for creating dramatic localized lighting effects.
They are defined by their position, the direction in which they are pointing, and the width of the beam of light they produce. At , the spotlight intensity is zero. If neither angle is given, they both are effectively set to 180 degrees. Extended sources are meant to model spherical light sources. If you do not specifically desire penumbrae in your image, use a point source instead.