+/**
+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.
+
+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.
+*/