The Illuminated Surface is a specialized ray release feature that produces reflected or refracted light directly at a surface. This can be used, for example, when the direction of incident radiation is known, but its propagation is not interesting until it has already been reflected once by an object.

The Solar Radiation computes the initial direction of rays as if they were solar rays being released at a specified latitude, longitude, date, and time. Instead of the latitude an longitude, you can also select from a list of built-in cities.