Mehrstufige Verdeckung unter Verwendung eines Maskenpuffers

摘要

Occulting apparatus (40) for use with an image generator (10) that provides for multiple-level occulting of image data. The occulting apparatus (30) comprises a mask buffer (50) and control logic (40) for processing image data to construct and store an obscurance mask in the mask buffer. Foreground entities contained in the image data are logically ORed into the mask buffer until the entities extend beyond a predefined range from a predetermined image viewpoint. Thereafter, the mask is used by the control logic to reject entities contained in subsequently processed image data that are fully obscured by the foreground entities comprising the obscurance mask. The control logic (40) includes an obscurance manager (41), a region processor (42), an object processor (43), a polygon processor (44), and insertion logic (45). The obscurance manager (41) is a controller for building and applying the obscurance mask to the image data. The region, object, and polygon processors (42, 43, 44) respectively process regions, objects, and polygons in the image to determine if they are obscured, reject obscured entities, and transmits unobscured entities to subsequent processors. The insertion logic (45) processes unobscured polygons and applies them to the obscurance manager (41) for storage and use by the respective region, object, and polygon processors (42, 43, 44). The present invention performs real-time occulting of all objects in an image scene, whether they are fixed or moving. Hidden area modules (large groups of objects in a geographic region), single objects, polygons, and pixels are sequentially filtered-out in real-time. The mask buffer (50) and control logic (40) provide three levels of occulting. A hybrid Z-buffer (51) provides pixel-level occulting. The present invention rejects regions, objects, and polygons, early in the graphics processing pipeline to reduce the number of required pixel processing computational elements in the image generator. By rendering objects generally from front to back, entities that are completely hidden by nearer objects can be detected and discarded before tiling and pixel processing.