[GD-Windows] mutiple cameras

[Brett B. <res...@ga...>]

What is the recommended way to handle multiple cameras/views per "window" in
both DirectX and OpenGL (e.g. a car racing game with a rear view mirror, or
split screen 2 player)?  For example, for DX is it normal to use additional
swap chains for each camera viewport or to use render targets for each
camera and then copy the surface to the framebuffer when done?  Or is there
another way?  How about OpenGL?
Cheers,
-bb