US 5,706,479 AGranted

Method and apparatus for dynamically detecting overflow of a multi-layer buffer

AssigneeApple Computer, Inc.

InventorsStephanie Winner, Michael Kelley

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Abstract

In a computer graphic system a method and apparatus for dynamically maintaining an overflow flag in a multi-layer buffer. A circuit for maintaining an overflow signal is provided. This circuit is provided new pixel data from the computer system and old pixel data from a memory and in response dynamically asserts or de-asserts the overflow signal. An increment and decrement generator, which is coupled to the new overflow generator, is provided a new overflow signal and an old overflow signal and in response generates an increment signal and a decrement signal. An overflow tracking circuit, which is coupled to the increment and decrement generator, is provided. The overflow tracking circuit uses the increment and decrement signals to maintain an overflow count value.

Claims21

Dependent claims

For a computer graphics system having a display device and a multi-layer buffer, said display device having at least one region, said region having a plurality of pixels for displaying geometric entities, said buffer having a pixel data storage location for each pixel of said region, each pixel data storage location for storing more than one geometric entity's pixel data for its pixel, a method of dynamically detecting buffer overflows, said method comprising the steps of:

(a) initializing an overflow count value to a predetermined value, said overflow count value indicating number of overflowed pixel storage locations;
(b) submitting pixel data for a geometric entity to said multi-layer buffer;
(c) attempting to store said geometric entity's pixel data in said buffer at a pixel storage location for the pixel identified by said geometric entity's pixel data;
(d) if said pixel storage location was not overflowed prior to said attempt but is overflowed after said attempt, incrementing in a first direction said count value by a predetermined unit;
(e) if said pixel storage location was overflowed prior to said attempt but is not overflowed after said attempt, decrementing in a second direction opposite said first direction said count value by said predetermined unit;
(f) repeating steps (b) through (e) until all geometric entities' pixel data in said region have been submitted for storing in said multi-layer buffer.

3 more elements

For a computer graphics system having a display device and a multi-layer buffer, said display device having a first region, said first region having a plurality of sub regions, said first region having a plurality of pixels for displaying geometric entities, said buffer having a pixel data storage location for each pixel of said first region, each pixel data storage location for storing more than one geometric entity's pixel data for its pixel, a method of dynamically detecting buffer overflows, said method comprising the steps of:

(a) initializing a first region overflow count value and a plurality of sub region count values to a predetermined value, wherein said first region overflow count value indicates number of overflowed pixel storage locations for all pixels of said first region, and each of said sub region count value indicates number of overflowed pixel storage locations for all of its pixels
(b) submitting pixel data for a geometric entity to said multi-layer buffer;
(c) attempting to store said geometric entity's pixel data in said buffer at a pixel storage location for the pixel identified by said geometric entity's pixel data;
(d) if said pixel storage location was not overflowed prior to said attempt but is overflowed after said attempt, incrementing by one (i) said first region count value, and (ii) the sub region count value for the sub region in which said identified pixel is in;
(e) if said pixel storage location was overflowed prior to said attempt but is not overflowed after said attempt, decrementing by one (i) said first region count value, and (ii) the sub region count value for the sub region in which said identified pixel is in;
(f) repeating steps (b) through (e) until all geometric entities' pixel data have been submitted for storing in said buffer.

3 more elements

A method for dynamically removing an overflow for a pixel storage location, said pixel storage location including a predetermined number of pixel data, said method comprising the steps of:

a) receiving a first Z value and a first opaque signal, said first Z value and said first signal associated with a first pixel data, said first opaque signal indicating whether the first pixel data is opaque or transparent;
b) receiving a second Z value and a second opaque signal, said second Z value and second opaque signal being associated with a second pixel data, said second opaque signal indicating whether the second pixel data is opaque or transparent;
c) further receiving a second overflow signal associated with the second pixel data;
d) dynamically clearing the second overflow signal based upon the first Z value, the first opaque signal, the second Z value and the second opaque signal;
and
e) assigning the first Z value and the first opaque signal with the second Z value and the second opaque signal, respectively, and assigning a first overflow signal with the second overflow signal.

3 more elements

A computer graphics system having a pixel storage location, said pixel storage location including a pixel data, said computer graphics system comprising:

a) means for providing a first Z value and a first opaque signal, said first Z value and said first signal associated with a first pixel data, said first opaque signal indicating whether the first pixel data is opaque or transparent;
b) means for providing a second Z value and a second opaque signal, and a second overflow signal, said second Z value and, second opaque signal, and second overflow signal being associated with a second pixel data, said second opaque signal indicating whether the second pixel data is opaque or transparent;
and
c) means coupled to the first and second providing means for dynamically maintaining the second overflow signal.

1 more element

Dependencies are inferred from the claim text.