Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1997-09-04
2001-04-17
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S440000, C345S182000
Reexamination Certificate
active
06219062
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to three-dimensional graphics display techniques for displaying three-dimensional figures (i.e., 3D graphics) and, more particularly, to a three-dimensional graphics display apparatus for executing at high speed what is known as a “fog” display process to enhance the 3D or cubic display effect.
To implement a three-dimensional graphics display requires incorporating as many aspects of the real world as possible into a display so that the display imitates reality as closely as possible.
One technique for accentuating natural phenomena is that of displaying a fog scene. To display a fog scene involves: distinctly indicating foreground objects and figures (simply called objects hereunder), making the image of the objects foggier the farther they are located from the foreground, and having objects completely fogged out beyond a certain distance.
A similar technique is sometimes used to implement what is known as a depth queuing effect. This technique involves displaying objects more darkly the farther they are located from the foreground (i.e., in the depth direction), and not displaying at all those objects beyond a certain distance or depth (expressed in Z value; the distance or depth is simply called the Z value hereunder). The technique is designed to emphasize the sense of depth so as to bring about a more pronounced 3D display stage.
The aforementioned effects (generically called the fog effect hereunder) are discussed illustratively in Open GL Reference Manual (from Addison-Wesley Publishing Company, p. 128). The publication introduces the following three algorithms:
f=(end−z)/(end−start) (Exp. 1.1)
where, “start” stands for the Z value of a figure starting to be fogged, “end” denotes the Z value beyond which objects are completely fogged in, “z” represents the Z value of the figure to be drawn, and “f” indicates the density of fog (common to the remaining two algorithms).
f=
e
{circumflex over ( )}−(density×z) (Exp. 1.2)
where, symbol {circumflex over ( )} represents a power exponent and “density” stands for a constant.
f=
e
{circumflex over ( )}−(density×z){circumflex over ( )}2 (Exp. 1.3)
Drawing data and/or display data is generated by use of the fog density value “f” from the above calculations and on the basis of color data and/or figure data.
With the above technique, the value “f” is acquired using the Z value of each pixel as the base for the calculations. This requires handling computations of exponentiation.
Therefore, one disadvantage of the conventional technique is that, with so much data to compute, a large amount of hardware is needed to realize high-speed processing.
Another disadvantage is that the calculations involved relegate the selection of the algorithm to application programs. The algorithm cannot be selected fixedly by hardware.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a three-dimensional graphics display apparatus, which is structured simply, yet is capable of implementing a display involving the fog effect at high speed.
It is another object of the present invention to provide a three-dimensional graphics display apparatus having a fog effect display capability realized through the use of any one of a plurality of algorithms.
In carrying out the invention and according to a first aspect thereof, there is provided a three-dimensional graphics display apparatus comprising: a Z value generation device for generating depth data on either a figure or an object pixel for a pixel to be displayed; a display color data holding device for holding display color data to be used for display; a blend coefficient calculation device for calculating a blend ratio coefficient representing a color blend ratio of color data on either a figure or an object to be drawn on the basis of the Z value, with respect to the display color data; and a color data blending device for generating fog display color data by operating on the color data and the display data in accordance with the calculated blend ratio coefficient.
According to a second aspect of the invention, there is provided a three-dimensional graphics display apparatus comprising:a Z value generation device for generating depth data on either a figure or an object pixel for a pixel to be displayed; a display color data holding device for holding display color data to be used for display; a blend coefficient calculation device for calculating a blend ratio coefficient representing a color blend ratio of color data on either a figure or an object to be drawn on the basis of the Z value, with respect to the display color data; a blend ratio coefficient table for holding the blend ratio coefficient calculated with respect to a generated Z value; a table reference device for reading the Z value of a figure to be displayed and then reading from the blend ratio coefficient table the blend ratio coefficient corresponding to the read-out Z value; and a color data blending device for generating fog display color data by operating on the color data and the display data in accordance with the blend ratio coefficient read out by the table reference device.
The Z value generation device generates depth data (i.e., Z values) of each figure or object to be displayed. Based on the Z values thus calculated, the blend coefficient calculation device calculates a fog blend ratio for each of the pixels involved. In accordance with the calculated ratio, the color data blending device blends the color data on the figure or object with fog color data from the display color data holding device. This makes it possible to provide the appropriate fog effect on a pixel by pixel basis.
The blend ratio coefficient table stores the blend ratio coefficient (i.e., fog coefficient) corresponding to the depth data (Z values) on each figure or object. The coefficients are calculated in advance and the results are set in the table.
Where a figure is to be drawn, the blend ratio coefficient is calculated by referencing the table settings corresponding to the Z value for each of the pixels involved.
The blend ratio coefficient is acquired per pixel in the manner described. Fog display color data is then generated on the basis of the obtained blend ratio coefficient and in accordance with the color data and display color data on the figure or object in question.
Because blend ratio coefficients are stored beforehand in the table, complicated arithmetic processing is not needed in the coefficient computations in increments of pixels. This translates into a higher processing speed and a reduction in hardware.
Switching from one algorithm to another for computations is also made possible by modifying the table contents.
REFERENCES:
patent: 5007101 (1991-04-01), Iwahashi et al.
patent: 5490239 (1996-02-01), Myers
patent: 5724561 (1998-03-01), Tarolli et al.
patent: 7-21407 (1995-01-01), None
“Computer Graphics”: James D. foley, Andries van Dam, Steven K. Feiner, John F. Hughes; Section 17.3, 1992.*
In re Iwahashi (CA FC) 12 USPQ2d 1908, decided Nov. 7, 1989.
Matsuo Shigeru
Nakatsuka Yasuhiro
Sato Jun
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Padmanabhan Mano
Zimmerman Mark
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