Compositing

Your application can use the stencil buffer to composite 2-D or 3-D images onto a 3-D scene. A mask in the stencil buffer is used to occlude an area of the rendering target surface. Stored 2-D information, such as text or bitmaps, can then be written to the occluded area. Alternately, your application can render additional 3-D primitives to the stencil-masked region of the rendering target surface. It can even render an entire scene.

Games often composite multiple 3-D scenes together. For instance, driving games typically display a rear-view mirror. The mirror contains the view of the 3-D scene behind the driver. It is essentially a second 3-D scene composited together with the driver's forward view.