-Base class for renderable objects. All Renderables must support rendering with
-a Renderer, and may optionally provide support for standalone rendering.
-
-The render methods take a Tag to identify a render pass. It is most commonly
-used together with Techniques and Pipelines to implement multipass rendering.
+Base class for renderable objects. Rendering is performed with the help of a
+Renderer object.
+
+The render method takes a Tag to identify a render pass. It can be used with
+a Technique to select alternative rendering methods, such as simplified shaders
+for a depth-only shadow pass.
+
+The setup_frame and finish_frame methods provide a mechanism for performing
+once-per-frame operations. This is most useful for effects, which may need to
+do auxiliary rendering. With complex rendering hierarchies, these methods may
+be called multiple times for one frame, but it's guaranteed that no rendering
+will occur before a setup_frame call or after a finish_frame call.