Apparatus and method for using a test window in a graphics subsystem which incorporates hardware to perform clipping of images

摘要

An apparatus and method for using a test window to improve the efficiency of clipping and inter-coordinate images which are to be displayed by a graphic display subsystem. A test window is defined which surrounds a window (the clip window) within which it is desired to render graphical images. Objects are then tested to see if their vertices are outside the test window. The utilization of this window allows for a performance optimization to be made between processing of a clipped object by a hardware based graphics subsystem which incorporates the present invention or by graphic software executed by a general purpose CPU which also interfaces to the graphics display. By properly defining the test window size relative to the clip window, objects which fall totally within the test window, will be rendered faster by the graphics subsystem rather than deferring the object to graphics software. Objects with vertices that fall outside the test window would be deferred to graphics software to render.