Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1999-12-09
2002-10-29
Luu, Matthew (Department: 2779)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S422000, C345S428000, C345S581000, C345S611000, C345S505000, C348S497000, C348S638000, C348S668000, C358S518000, C358S525000, C358S534000, C382S269000
Reexamination Certificate
active
06473091
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus for performing so-called &agr;-blending and dithering and a method for the same.
2. Description of the Related Art
Computer graphics are often used in a variety of computer aided design (CAD) systems and amusement machines. Especially, along with the recent advances in image processing techniques, systems using three-dimensional computer graphics are becoming rapidly widespread.
In three-dimensional computer graphics, the color value of each pixel is calculated at the time of deciding the color of each corresponding pixel. Then, rendering is performed for writing the calculated value to an address of a display buffer (frame buffer) corresponding to the pixel.
One of the rendering methods is polygon rendering. In this method, a three-dimensional model is expressed as an composite of triangular unit graphics (polygons). By drawing the polygons as units, the colors of the pixels of the display screen are decided.
In polygon rendering, coordinates (x, y, z), color data (R, G, B, &agr;), homogeneous coordinates (s, t) of texture data indicating a composite image pattern, and a value of the homogeneous term q for the respective vertexes of the triangle in a physical coordinate system are input and processing is performed for interpolation of values inside the triangles.
Here, the homogeneous term q is, simply stated, like an expansion or reduction rate. Coordinates in a UV coordinate system of an actual texture buffer, namely, texture coordinate data (u, v), are comprised of the homogeneous coordinates (s, t) divided by the homogeneous term q to give “s/q” and “t/q” which in turn are multiplied by texture sizes USIZE and VSIZE, respectively.
FIG. 10
is a view of the system configuration of the basic concept of a three-dimensional computer graphics system.
In a three-dimensional computer graphics system, graphic drawing data and other data are given to a rendering circuit
5
having a rendering processor
5
a
and a frame buffer memory
5
b
from a main memory
2
of a main processor
1
or an I/O interface circuit
3
for receiving graphic data from the outside via a main bus
4
.
In the rendering processor
5
a
, a frame buffer
5
b
for holding data to be displayed and a texture memory
6
for holding texture data to be applied on the surface of a graphic element to be drawn (for example, a triangle) are connected.
The rendering processor
5
a
performs processing for drawing a graphic element applied with texture on its surface for every graphic element.
The frame buffer
5
b
and the texture memory
6
are generally configured by a dynamic random access memory (DRAM).
In the system in
FIG. 10
, the frame buffer
5
b
and the texture memory
6
are configured to be physically separate memory systems.
When drawing image data, &agr;-blending is performed for blending (R, G, B) data included in the current image data and (R, G, B) data already stored in the frame buffer
5
b
by a blending value indicated by &agr;-data corresponding to the current image data. Furthermore, dithering is performed for thinning the image data after the &agr;-blending in consideration of the capacity of the frame buffer
5
b
etc., then the dithered (R, G, B) data is written back to the frame buffer
5
.
In other words, &agr;-blending is processing for linear interpolation of two colors to apply a color between the two, while dithering is processing for adding noise data to the data subjected to the &agr;-blending and then thinning out the data to make a small number of colors appear as many colors.
FIG. 11
is a block diagram of an example of the configuration of an &agr;-blending circuit and a dithering circuit of the related art.
The &agr;-blending circuit
7
is composed of a multiplier
71
for multiplying current image data S (for example, an 8-bit integer expressing [0,255]) and a blending coefficient &agr; (for example, an 8-bit integer expressing [0,2]), a subtractor
72
for subtracting the blending coefficient &agr; from 1, a multiplier
73
for multiplying image data D already stored in the frame buffer memory
5
b
(for example, an 8-bit integer expressing [0,255]) and an output of the subtractor
72
, an adder
74
for adding an output of the multiplier
71
and an output of the multiplier
73
, and a clamp circuit
75
for extracting a valid value (for example, [0,255]) of a color value from the data obtained by the adder
74
.
In the &agr;-blending circuit
7
, as shown in
FIG. 11
, data &agr;×S+(1−&agr;)×D is obtained from input values S, D, and &agr; in the same way as the output of the adder
74
.
The dithering circuit
8
is configured by an adder
81
for adding error data E (for example, a 3-bit integer expressing [−4,3]) as noise data to an output signal S
7
of the &agr;-blending circuit
7
, a clamp circuit
82
for extracting a valid value of a color value from an output of the adder
81
, and a round-off circuit (dividing circuit)
83
for discarding (thinning out) the lower three bits of an output of the clamp circuit
82
and writing back the upper 5 bits to the frame buffer
5
b.
In the dithering circuit
8
, as shown in
FIG. 11
, data &agr;(S−D)+D+E is obtained from input values &agr;×S+(1−&agr;)×D and E in the same way as an output of the adder
81
.
Summarizing the problems to be solved by the invention, as explained as above, however, since the &agr;-blending circuit
7
and the dithering circuit
8
are separately provided and configured to be connected in series in an image processing apparatus of the related art, the size of the circuit becomes large and the calculation time becomes long, which are obstacles to high speed processing.
Also, in a so-called built-in DRAM system of the related art in the above three-dimensional computer graphics system, there have been the following disadvantages when a frame buffer memory and a texture memory are provided separately in separate memory systems.
That is, there is the disadvantage that a frame buffer emptied due to a change of the display resolution cannot be used as a texture buffer or the disadvantage that the performance has to be sacrificed because of the large overhead, such as page exchange, of the DRAM in simultaneous access of the frame buffer memory and the texture buffer memory when the two are made physically integral.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image processing apparatus which can reduce the size of the circuits for &agr;-blending and dithering, can realize high speed processing, enables use of a memory region emptied due to a change in the display resolution for texture applications, can prevent an increase of overhead for page exchange etc., and enables flexible and high speed processing without causing a decline in performance, and a method for the same.
To attain the above object, according to a first aspect of the present invention, there is provided an image processing apparatus for performing &agr;-blending and dithering on image data, comprising a storage circuit in which at least display image data is drawn and a logic circuit for finding data on the amount of update of present image data to be drawn from image data already stored in the storage circuit using a given blending coefficient &agr;, finding the data comprised of noise data added to the image data stored in the storage circuit, adding the two obtained data to find data comprised of the noise data added to data obtained by linear interpolation of two colors, extracting valid value of color from the data, thinning out the extracted data, and writing back the same to the storage circuit.
According to a second aspect of the present invention, there is provided an image processing apparatus for performing rendering by receiving polygon rendering data including three-dimensional coordinates (x, y, z), R (red), G (green), and B (blue) data, a blending coefficient
Iida Ryohei
Takemoto Takashi
Fulwider Patton Lee & Utecht LLP
Luu Matthew
Sajous Wesner
Sony Corporation
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