| 摘要 |
A method and apparatus for determining a rear most Z value for a pixel block is presented, where the pixel block is a portion of the image data for a frame as stored in a frame buffer. The frame buffer is stored in a DRAM memory structure that is included on an integrated circuit along with a render backend block that blends received fragments from a three-dimensional (3D) video graphics pipeline with the image data stored in the frame buffer. The 3D video graphics pipeline is located on a video graphics processing integrated circuit separate from the integrated circuit storing the frame buffer and render backend block. The integrated circuit storing the frame buffer includes a value determination block that determines the rear most Z value. The value determination block includes a data serialization block that serializes the bits corresponding to the Z values for the pixels included in the pixel block to produce a plurality of corresponding serial bit streams. A comparison tree is coupled to the data serialization block, and the comparison tree sorts through all of the serial bit streams corresponding to the Z values for the pixel block to determine the bit stream corresponding to the rear most Z value included in the pixel block. This resultant bit stream can then be converted to a parallel format and provided to the 3D video graphics pipeline for use in comparison operations to determine if certain primitives, or portions thereof, should be fully processed.
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