-Effects are used to wrap other renderables and give them additional visual
-properties. An Effect's render method should set up the necessary state, call
-the wrapped Renderable's render method, and clean up after itself.
+Base class for visual effects.
+
+Effects wrap other renderables and provide additional textures or uniform
+values which can be used by shaders to modify the appearance of the content
+renderable. Some material properties require certain Effects to be present in
+order to function properly.
+
+If an Effect subclass needs to do any sideband rendering to prepare for a
+frame, that should be done in setup_frame(). The render() function should only
+set up the necessary state and call the content renderable's render() function.