Three dimensional graphics system with early occlusion culling using Z-ranges

Abstract

An apparatus and a method for generating 3-dimensional computer graphic images. The image is first sub-divided into a plurality of rectangular areas ( 2 ). A display list memory ( 4 ) is loaded with object data for each rectangular area. The image and shading data for each picture element of each rectangular area are derived from the object data in the image synthesis processor ( 6 ) and a texturing and shading processor ( 10 ). A depth range generator ( 12 ) derives a depth range for each rectangular area from the object data as the imaging and shading data is derived. This is compared with the depth of each new object to be provided to the image synthesis processor ( 6 ) and the object may be prevented from being provided to the image synthesis processor ( 6 ) independence on the result of the comparison.

1 . A method for generating 3-dimensional computer graphic images comprising the steps of: 
 sub-dividing the image into a plurality of rectangular areas;    loading object data for each rectangular area into a display list memory;    deriving image data and shading data for each picture element of each rectangular area from the object data;    providing the shading data for display; characterised by:    deriving a range of depth values for each rectangular area from the object data;    comparing the depth of each new object to be provided to the image data deriving step for a rectangular area with the depth range for that rectangular area, and    preventing the new object data from being provided to the image data deriving step in dependence on the result of the comparison.    
     
     
         2 - 16 . (canceled)