Patent Document ID: 7812837
Application ID: 11741945
Patent Status: 1

Claim One:
1. A reduced Z-buffer generating method comprising: providing a reduced Z-buffer that stores, in a non-hierarchical manner, representative Z values for determining a positional relationship between plural objects or fragments constituting the objects in a depth direction, each representative Z value indicating one depth value, from a point of view, for a unit of once-grouped predetermined pixel blocks, each including a plurality of neighboring pixels; and comparing the Z values of respective rasterized pixels in a pixel block of an object or a fragment to be rendered with the representative Z value of a corresponding pixel block stored in the reduced Z-buffer, and updating the representative Z value of the pixel block with a farthest Z value if the farthest Z value indicates lying closer to the point of view than the representative Z value of the pixel block does, the farthest Z value indicating lying the farthest from the point of view among the per-pixel Z values in the pixel block, wherein the representative Z value of the pixel block in the reduced Z-buffer is updated only if the object or the fragment is rendered on all the pixels within the pixel block, and wherein when comparing the Z values of the rasterized pixels in the pixel block of the object or fragment to be rendered with the representative Z value of the corresponding pixel block stored in the reduced Z-buffer, the representative Z value is exclusively compared with: a Z value of a pixel at a vertex of a polygon of the object or fragment falling within the pixel block; a Z value of a pixel at an intersection between an edge of the polygon and a border of the pixel block; and the Z values of pixels located at the pixel block corners, among the four corners falling within the polygon.