You can render an existing SDL file from a command line by using one of the stand-alone render programs: renderer, raytracer, powercaster, and powertracer. By rendering from a command line you can render a batch of several SDL files at the same time; the only limitation is the amount of swap space available. (For this reason the stand-alone renderers are also referred to as batch renderers.) You can also specify options during command line rendering which override internal variables in the SDL file. This lets you change the behavior of the renderer without having to edit the SDL file.