Patent ID: 6768487
Filing Date: 2004-07-27
Classification: G06T

Abstract:
In a graphics system for rendering geometic objects, the graphics system including hierarchical depth buffer means having a plurality of levels ranging from a finest level to a coarsest level, the hierarchical depth buffer means organized as a plurality of nested tiles, each tile including a plurality of cells and each tile having a tile record, a method for determining whether a geometric object is occluded with respect to the hierarchical depth buffer means, the method comprising the steps of:initializing a stack of tile records with a tile record for a tile overlapped by the geometric object; testing whether the stack of tile records is empty, and if so, concluding that the geometric object is occluded and returning with processing complete; popping a tile record from the stack of tile records, which becomes the current tile; if the current tile is not at the finest level of the hierarchical depth buffer means, determining the cells within the current tile where the geometric object is potentially visible, creating a tile record corresponding to each potentially visible cell and pushing said tile record onto the stack of tile records, and returning to said testing step, if the current tile is at the finest level of the hierarchical depth buffer means, determining whether the geometric object is visible within the current tile, and if so, concluding that the geometric object is visible and returning with processing complete; and returning to said testing step.