Computer graphics processing and selective visual display system – Computer graphic processing system – Integrated circuit
Reexamination Certificate
1997-02-06
2001-01-30
Nguyen, Chanh (Department: 2775)
Computer graphics processing and selective visual display system
Computer graphic processing system
Integrated circuit
C345S520000
Reexamination Certificate
active
06181354
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to image generation.
As shown in
FIG. 1
, for purposes of simulating the motion of objects
8
in a three-dimensional (3-D) image
6
, a typical graphics system generates and displays successive frames (i.e., snapshots) of the image
6
. The graphics system may update the position, orientation, and viewpoint of all the objects
8
for each frame.
However, to reduce the required memory bandwidth and memory capacity, the graphics system may take advantage of the fact that some objects
8
a
(e.g., background objects farther from the viewer) do not require updates as frequently as other objects
8
b
(e.g., foreground objects closer to the viewer). As shown in
FIG. 2
, a graphics system
10
recognizes this advantage by dividing the image
6
into image layers (typically parallel with the X-Y plane) with each image layer containing one or more objects
8
. The graphics system
10
selectively updates the image layers (i.e., the objects in the image layers) according to a rate at which the image layer changes which allows some objects (e.g., foreground objects) to be updated more frequently than other objects (e.g., background objects).
The physical properties (e.g., size and appearance) of each object
8
are typically defined by a data structure
12
(e.g., a “sprite”) stored in a memory
15
. To perform affine transformations (e.g., rotation and translation) of the objects
8
of a selected image layer, the graphics system
10
has a polygon object processor
14
. An image layer compositor
16
combines the image layers (whether updated or not) to form image data which a video output circuit
22
uses to form horizontal scan lines (and thus, the image
6
) on a display
26
(FIG.
3
).
To form a frame of an image, the video output circuit
22
generates the horizontal scan lines in a predetermined sequence. Each scan line is generated in a left to right fashion across the display
26
, and to generate one frame (assuming no interlacing) the sequence begins at the top (i.e., for the first scan line) and ends at the bottom (i.e., for the last scan line) of the display
26
.
The compositor
16
forms the image data in a piecewise fashion by subdividing the image
6
along an X-Y plane into horizontal bands
24
(i.e., blocks of scan lines) extending across the screen
26
. The compositor
16
forms the image data for each band
24
inside a compositing buffer
18
. To minimize delays between the forming of the image data of the band
24
and the retrieving of image data by the video output circuit
22
, the compositing buffer
18
has two band buffers
20
used alternatively by the video output circuit
22
and the image layer compositor
16
. The image layer compositor
16
forms image data for one of the bands
24
in one band buffer
20
while the video output circuit
22
simultaneously retrieves the image data for another one of the bands
24
from the other buffer
20
.
SUMMARY OF THE INVENTION
The invention provides a graphics system that allows a region of memory to be updated with data while the same region of memory is being used to generate scan lines. In this manner, the graphics system stores image data for a first set of scan lines (e.g., a horizontal band of scan lines) in the region of memory. Data for a second set of scan lines which sequentially follow the first set of scan lines (e.g., an adjacent horizontal band of scan lines) may be stored in the same region of memory before all of the image data for the first set of scan lines is retrieved. As a result, an entire frame of the image may be generated using a region of memory no larger than that required to store the image data for a few scan lines (e.g., one horizontal band of scan lines).
In general, in one aspect, the invention features a method for use with a display capable of displaying a frame of an image via a sequence of scan lines. The method includes storing data associated with one or more scan lines of the frame in a region of a memory. The data is retrieved from the region, and one or more scan lines are formed on the display using the data. Before all of the data is retrieved from the region, other data associated with the next scan line in the sequence is stored in the region of the memory. This other data is used to form the next scan line in the sequence after the other scan lines are formed.
In preferred embodiments, the data has at least one data patch associated with a portion of the image, and the portion of the image has a maximum scan oriented dimension less than the predetermined scan dimension. The data patches are substantially the same size. Each data patch includes multiple subsets of data, and each of the multiple subsets of data is associated with one of the scan lines. The subsets of data are associated with exactly one scan line. The image has horizontal bands, and the data patches form one of the horizontal bands. Some of another data patch is stored in the memory outside of the first region. The scan lines are substantially horizontal. Storing the data in the memory includes compressing the data to form compressed data and transferring the compressed data to the memory. The region has rows and columns, and storing the data in the memory includes alternating the storage of the data associated with some of the scan lines and the other data between the rows and columns of the region.
In general, in one aspect, the invention features a method for use with a graphics system capable of furnishing data representative of an image and having a display capable of displaying the image via scan lines. Each of the scan lines has a predetermined scan dimension. The method includes forming a data patch associated with a portion of the image. The portion of the image has a maximum scan oriented dimension less than the predetermined scan dimension. The data patch is used to generate at least one of the scan lines on the display.
In preferred embodiments, the image has horizontal bands of scan lines. Each horizontal band has a scan oriented dimension close to the predetermined scan dimension. The data patch is stored in a memory that is used to store data associated with one of the horizontal bands, and more than one data patch is stored in the memory to form the data associated with one of the horizontal bands. The data furnished by the graphics system includes image layers of the image, and portions of the image layers are combined to form the data patch. The portion of the image is substantially rectangular. Other data patches stored in the memory are used to form one scan line on the display.
In general, in another aspect, the invention features a graphics system for use with another system capable of furnishing data representative of an image and having a display capable of displaying the image via scan lines. Each of the scan lines has a predetermined scan dimension. The graphics system has a patch generator connected to form a data patch associated with a portion of the image. The portion of the image has a maximum scan oriented dimension less than the predetermined scan dimension. The graphics system also has a display interface connected to use the data patch to generate at least one of the scan lines on the display.
In general, in another aspect the invention features a graphics system for use with a display capable of displaying a frame of an image via a sequence of scan lines. The graphics system has a memory and an image generator. The image generator is connected to store the data associated with some of the scan lines of the frame in a region of the memory, and before all of the data is retrieved from the region, store other data associated with another scan line in the region. The graphics system also has a display interface that is connected to retrieve the data associated with some of the scan lines from the region and use the data to form some of the scan lines on the display. The display interface is also connected to use the other data to form the next scan line in the sequence after the other scan lines are formed.
Other
ATI Technologies Inc.
Nguyen Chanh
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