-organize Renderables within a pass. A Camera can be specified for the entire
-Pipeline.
-
-A Pipeline is also a Renderable itself. It will only respond to the default
-pass. The Renderables within the Pipeline will be invoked with whatever tags
-were specified when adding them.
-
-A Pipeline's render method should normally be called without a Renderer; it
-will create one itself, using the camera specified for the Pipeline. If a
-Renderer is passed, its camera will be used instead.