International Business Machines Corporation

Roland M Hochmuth

William Louis Luken

David C Tannenbaum

Douglas P Moore

A computer graphics system reduces the number of lighting calculations required to render a scene having objects illuminated by light sources by classifying each primitive for objects in an illuminated scene as either hidden or visible using a z-buffer. In a first approach, only one pass is made through the display list of primitives for the scene, and lighting calculations are performed only for primitives classified as visible. In a second approach, two passes are made through the display list. In the first pass, the display list is fully traversed to set-up the z-buffer, and no lighting calculations are performed. When the second pass of the display list is performed, each primitive is classified as hidden or visible, and lighting calculations are performed for each primitive classified as visible as the display list is traversed. Lighting calculations may be performed using either Gouraud or Phong shading.

Method and apparatus for reducing illumination calculations through

A method and system for processing a graphics data stream in a computer graphics system having a parallel processing system. The graphics data stream includes a plurality of elements. The method and system of the present invention involve associating tags with elements in a graphics data stream, wherein each tag indicates a display order for the element associated with the tag. The elements are processed within a parallel processing system to produce processed elements, wherein each of the processed elements maintains an association with a tag. The processed elements are rasterized in a selected sequence to determine new pixel data sets, wherein rasterization of each processed element results in a new pixel data set for each of a plurality of pixels. Each new pixel data set includes order data derived from a tag associated with each of the processed elements. For each new pixel data set resulting from the rasterization of the processed elements, a current pixel data set is determined in response to a comparison of order data in the new pixel data set with order data in an existing pixel data set for each of the pixels. The pixels are then displayed within a display device utilizing the current pixel data sets associated with each of the pixels, wherein the plurality of elements is displayed in an order indicated by the associated tags to form a image.

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Woodstock, NY, United States of America

Roland M Hochmuth