Computer graphics processing system, computer memory, and method of use with computer graphics processing system utilizing hierarchical image depth buffer

A computer graphics method for use in rendering a portion of an object onto a two-dimensional image plane, the computer graphics method comprising:

• identifying a selected pixel corresponding to the portion of the object to be rendered;
• reading data items from a hierarchical image depth buffer, the data items including a near depth value and a far depth value for a foreground subset of a set of pixels and a near depth value for a background subset of the set of pixels, the hierarchical image depth buffer associated with a plurality of depth values for the set of pixels, the set of pixels including the selected pixel;
• and
• performing a comparison between the selected pixel and the data items to make a pixel visibility determination.

A computer graphics processing system comprising:

• an image depth buffer;
• a hierarchical image depth buffer, the hierarchical image depth buffer containing a plurality of entries, each of the plurality of entries associated with a plurality of depth values within the image depth buffer;
• and
• a processor having access to the image depth buffer and to the hierarchical image depth buffer, the processor including a computer graphics routine for use in rendering a portion of an object onto a two-dimensional image plane, the computer graphics routine comprising:
• identifying a selected pixel corresponding to the portion of the object to be rendered;
• reading an entry from the hierarchical image depth buffer, the entry containing a set of data items, the set of data items of the hierarchical image depth buffer associated with a plurality of depth values within the image depth buffer, the plurality of depth values for a set of pixels, the set of pixels including the selected pixel, the set of data items including a near depth value of a foreground subset of the set of pixels, a far depth value of the foreground subset, and a near depth value of a background subset of the set of pixels;
• and
• performing a computation with respect to the selected pixel and the set of data items, to make a pixel visibility determination.

A computer graphics processing system comprising:

• an image depth buffer;
• a hierarchical image depth buffer, the hierarchical image depth buffer containing a plurality of entries, each of the plurality of entries associated with a plurality of depth values within the image depth buffer;
• and
• a processor having access to the image depth buffer and to the hierarchical image depth buffer, the processor including a computer graphics routine for use in rendering a portion of an object onto a two-dimensional image plane, the computer graphics routine comprising:
• identifying a selected pixel corresponding to the portion of the object to be rendered;
• reading an entry from the hierarchical image depth buffer, the entry containing a set of data items, the set of data items of the hierarchical image depth buffer associated with a plurality of depth values within the image depth buffer, the plurality of depth values for a set of pixels, the set of pixels including the selected pixel;
• and
• performing a computation with respect to the selected pixel and the set of data items, to make a pixel visibility determination;
• and
• wherein the set of data items includes a flag for each pixel in the set of pixels a flag set identifies a corresponding pixel that has been rendered.

A memory for use with a computer graphics processing system, the memory comprising:

• an image depth buffer containing a plurality of image depth values;
• a hierarchical image depth buffer, the hierarchical image depth buffer containing a plurality of entries, each of the plurality of entries associated with a set of the plurality of depth values within the image depth buffer, the set containing more than one depth value, at least one of the entries containing a near depth value and a far depth value corresponding to the set of the plurality of depth values;
• and
• a third level hierarchical buffer containing a plurality of initialization flags, each of the initialization flags for a super-block of pixels corresponding to a plurality of the entries within the hierarchical image depth buffer.