Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
2001-02-08
2004-05-25
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S421000, C345S619000, C341S067000
Reexamination Certificate
active
06741243
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to graphics processing in a computer system, and more particularly to a method and system for more efficiently rendering a graphical image.
BACKGROUND OF THE INVENTION
A conventional computer graphics system can display a graphical image on a display. The display includes a plurality of display elements, known as pixels, typically arranged in a grid. In order to display objects, the conventional computer graphics system typically breaks the objects into a plurality of polygons. The conventional system then typically renders the polygons in a particular order. For a three-dimensional scene, the polygons are generally rendered from back to front as measured from the viewing plane of the display. Similarly, a two-dimensional scene can be displayed where polygons are rendered based on their layer. Shallower layers occlude deeper layers.
For example,
FIG. 1
is a block diagram of a display
1
depicting a graphical image. The display includes a plurality of pixels
8
, only one of which is labeled. The graphical image includes primitives
2
,
3
,
4
,
5
, and
6
which may be part of one or more objects. Each of the primitives
2
,
3
,
4
,
5
, and
6
may cover several pixels and includes a plurality of fragments. Each fragment includes data for a pixel intersected by the corresponding primitive. Thus, a fragment may include data relating to the color, texture, &agr; values, and depth values for a particular primitive and a particular pixel.
One conventional method used in rendering the graphical image renders the image primitive by primitive in a particular order. For a three-dimensional scene, the primitives are generally rendered from back to front as measured from the viewing plane of the display. Similarly, a two-dimensional scene can be displayed where primitives are rendered based on their layer. Shallower layers occlude deeper layers. For example, the primitive
2
might be rendered first, followed in order by primitives
3
,
4
,
5
, and
6
.
FIG. 2A
depicts another conventional method
10
for rendering a graphical image.
FIG. 2B
depicts a display
20
including the primitives
2
,
3
,
4
,
5
, and
6
which are rendered using the conventional method
10
. Referring to
FIGS. 2A and 2B
, in order to render the graphic image, portions of the display
1
are rendered one at a time. Thus, a plurality of tiles, each tile having a fixed size, is defined, via step
12
. A tile is typically a two-dimensional rectangle containing n ×m pixels. The tiles
21
,
22
,
23
,
24
,
25
,
26
,
27
,
28
, and
29
are depicted in the display
20
. The primitives
2
,
3
,
4
,
5
, and
6
, or portions thereof, are then rendered tile by tile and primitive by primitive. For example, the portion of the primitive
2
in tile
21
is rendered first. When tile
21
has completed rendering, the portion of the primitive
4
in tile
22
is rendered. When tile
22
is completed, the portions of the primitives
4
and
6
in tile
23
are rendered. This process continues, rendering the graphical image primitive by primitive and tile by tile, until all primitives in all tiles have been rendered.
Although these conventional methods function, one of ordinary skill in the art will readily realize that it is desirable to provide data for an image in raster order. Furthermore, it would desirable if the image is efficiently rendered. Consequently, STELLAR SEMICONDUCTOR of San Jose, Calif. developed a system for rendering a graphical image pixel by pixel, in raster order. Raster order is from left to right and top to bottom across the display
1
. This system is described in U.S. patent application Ser. No. 08/624,261, entitled “METHOD AND APPARATUS FOR IDENTIFYING AN ELIMINATING THREE-DIMENSIONAL OBJECTS VISUALLY OBSTRUCTED FORM A PLANAR SURFACE” filed on Mar. 29, 1996 now Pat. No. 5,926,181, and assigned to the assignee of the present application and in co-pending U.S. patent application Ser. No. 08/624,260, entitled “GRAPHICS PROCESSORS, SYSTEM AND METHOD FOR GENERATING SCREEN PIXELS IN RASTER ORDER UTILIZING A SINGLE INTERPOLATOR” filed on Mar. 29, 1996 now Pat. No. 5,933,210, and assigned to the assignee of the present application.
FIG. 3
depicts a high-level block diagram of one embodiment of such a computer graphics system
50
. The system
50
includes a central processing unit (CPU)
52
, a display
54
, a user interface
56
such as a keyboard or mouse or other communicating device, a memory
58
, and an image generating unit
60
coupled with one or more buses
58
. The display
54
includes a display, such as the display
1
. The display
14
also includes a display memory
55
to which data for pixels are written prior to being shown on the display
1
. In order to display graphical images, the objects are broken into polygons to be used in rendering the objects. In a preferred embodiment, the polygons are rendered in raster order. That is, portions of the polygons are rendered pixel by pixel in the order of the pixels in the display
54
.
The image generating unit
60
is used in rendering the graphical image. The image generating unit includes an interface
61
connected to the bus
58
. The interface
61
transmits data to a data processing unit
62
. The block of processors
64
identifies data describing portions of primitives (“intersecting primitives”) which intersect the area extending along a z-axis from a selected pixel in an x-y plane corresponding to a screen of the display
14
. The block of processors
64
may include a number of processors, allowing intersecting primitives to be processed in parallel. By processing the primitives in parallel, the block of processors
64
can provide an indication of the fragments that intersect pixels currently being processed in a particular scan line. An obstructed object identifier/removal unit (Quick Z)
66
receives at least a portion of the fragment from each intersecting polygon associated with the selected pixel and removes portions of the fragments for intersecting polygons that are obstructed.
The interpolator
68
receives the remaining fragments for the intersecting polygons for the selected pixel and interpolates the data, including interpolating texture, color, and alpha values for the fragment. The interpolator
68
also provides a coverage mask for each fragment. The coverage mask indicates the portion of the pixel that the fragment covers. The fragments for remaining intersecting polygons are provided by the interpolator
68
to a hardware sorter
70
. The hardware sorter
70
sorts the fragments for the intersecting polygons based on the value of a key such as the z value, or depth value, for the fragment.
An antialiasing/blending/accumulating unit
72
performs antialiasing using the mask provided by the interpolator
68
. The antialiasing unit
72
may multiple units used in antialiasing, accumulating data, and blending data. The antialiased data is provided to the display
14
pixel by pixel in raster order.
Although the above-mentioned co-pending applications function well for their intended purpose, the processors in the block of processors
64
may overflow. In order to render the images in raster order, a number of the primitives intersecting pixels in a particular scan line (a row of pixels on the display
1
) are processed in parallel. There are also a finite number of processors in the block of processors
64
. For example, in one embodiment, sixty-four processors are provided in the block of processor block
64
. When a particular scan line contains a large number of primitives, more primitives than processors in the block of processors
64
may be attempted to be processed in parallel. The block of processors
64
may then overflow. Such an overflow is undesirable. Furthermore, efficient rendering of the graphical image is desired.
Accordingly, what is needed is a system and method for efficiently rendering a graphical image. It would be desirable if an overflow of processors can be avoided. The present invention addresses such a need.
SUMM
Kochubievski Vadim
Lewis Michael C.
Nissen Glenn
Bella Matthew C.
Broadcom Corporation
Monestime Mackly
Sawyer Law Group LLP
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