Table of Contents Glide Programming Guide

3Clipping

The grClipWindow() routine has four parameters that define the clipping rectangle. The values must be less than or equal to the current screen resolution and greater than or equal to 0; otherwise, they will be ignored. Glide does not perform any geometric clipping outside of supporting a hardware clipping window. For optimal performance, an application should perform proper geometric clipping before passing any primitives to Glide. The clipping window should not be used in place of true geometric clipping.

The default values for the clip window are the full size of the screen: (0,0,640,480) for 640´480 mode and (0,0,800,600) for 800´600 mode. To disable clipping, simply set the size of the clip window to the screen size. The Voodoo Graphics subsystem’s clipping window should not be used for general purpose primitive clipping; since clipped pixels are processed but discarded, proper geometric clipping should be done by the application for best performance. The Voodoo Graphics subsystem’s clip window should be used to prevent stray pixels that appear from imprecise geometric clipping. Note that if pixel pipeline is disabled, clipping is not performed on linear frame buffer writes (see Chapter Chapter 11. for more information).