A system and method for performing viewport clipping for multiple
viewports using a pipeline. The pixel address coordinates are compared
against boundaries of a first viewport window. The results of this
comparison, along with the pixel address coordinates, are registered and
passed on to the next pipeline stage. There, the pixel address
coordinates are compared against the boundaries of a second viewport
window. The comparison results are combined with those passed from the
previous stage, and the results are again registered. This scheme is
repeated until the pixel has been tested against all the viewport window
boundaries, with the intermediate results being combined into a single
result indicative of whether the pixel is to be passed to the subsequent
stages of the graphics pipeline or clipped.