Prepares rendering of the next frame.
This method is called before IRenderable.Render, when the graphics context has not yet begun to render the scene.
All setup work that does not require a graphics context (e.g. matrix computation, per-frame visibility determination) should be done here. This can help to maximize parallelism between the CPU and the GPU.
It is expected that the GPU is busy processing the render commands of the last frame, while this method prepares the next one.