Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1998-09-11
2003-08-26
Nguyen, Phu K. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
Reexamination Certificate
active
06611262
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to coding and decoding apparatus and method for recording a moving picture signal on a recording medium such as an optical disc or a magnetic tape and reproducing it for display on a display device. The present invention may be used in video conference systems, video telephone systems, broadcast equipment, multimedia database retrieval systems, and the like in such a manner that a moving picture signal is transmitted from a transmission side to a reception side via a transmission line and received and displayed on the reception side. The present invention may also be used for editing and recording a moving picture signal.
In a video conference system or a video telephone system in which a moving picture signal is transmitted to a remote place, to efficiently utilize a transmission line, an image signal is compressed/coded by utilizing line correlation or frame correlation of the video signal. In recent years, with improvement in computer processing, moving picture information terminals using a computer have become widespread. In such systems, information is transmitted to remote locations via a transmission line such as a network. In this case, to efficiently utilize the transmission line, a signal to be transmitted such as an image, sound, or computer data is transmitted after being compressed/coded. On a terminal side (reception side), the compressed/coded signal that has been transmitted is decoded by a predetermined decoding method corresponding to the encoding method into an original image, sound, or computer data, which is output by a display device, speakers, or the like of the terminal. Previously, the transmitted image signal or the like was merely output, as it is, on a display device. But in information terminals using a computer, a plurality of images, sounds, or computer data can be handled or displayed in a two-dimensional or three-dimensional space after being subjected to a given conversion process. This type of process can be realized in such a manner that information of a two-dimensional or three-dimensional space is described by a given method on a transmission side, and the terminal side (reception side) executes a conversion process on an image signal or the like according to the description.
A typical example for describing spatial information is VRML (Virtual Reality Modeling Language), which has been standardized by ISO-IEC/JTC1/SC24. The latest version VRML 2.0 is described in IS14772. VRML is a language for describing a three-dimensional space and defines data for describing attributes, shapes, etc. of a three-dimensional space. Such data is called a node. To describe a three-dimensional space, it is necessary to describe in advance how to combine the nodes. Each node includes data indicating color, texture, etc., data indicating polygon shapes, and other information.
In information terminals using a computer, a given object is generated by CG (computer graphics) according to a description of the above-mentioned VRML using polygons etc. With VRML, it is possible to attach a texture to a three-dimensional object that has been generated in this manner and that has been composed of polygons. A node called “Texture” is defined for still pictures and a node called “MovieTexture” is defined for moving pictures. Information (a file name, display start time or end time, etc.) on the texture to be attached is described in these nodes. Referring to
FIG. 23
, a texture attachment process (hereinafter referred to as a texture mapping process, where appropriate) will be described.
FIG. 23
shows an example of the configuration of texture mapping apparatus. As shown in
FIG. 23
, a memory group
200
includes a texture memory
200
a
, a gray scale memory
200
b
, and a three-dimensional object memory
200
c
. The texture memory
200
a
stores texture information that is input externally. The gray scale memory
200
b
and the three-dimensional object memory
200
c
store key data indicating the degree of penetration/transparency of the texture and three-dimensional object information that are also input externally. The three-dimensional object information is necessary for generation of polygons and is related to illumination. A rendering circuit
201
generates a three-dimensional object by generating polygons based on the three-dimensional object information that is stored in the three-dimensional object memory
200
c
of the memory group
200
. Further, based on the three-dimensional object data, the rendering circuit
201
reads out the texture information and the key data indicating the degree of penetration/transparency of the texture from the memories
200
a
and
200
b
, respectively, and executes a superimposition process on the texture and a corresponding background image by referring-to the key data. The key data indicates the degree of penetration of the texture at a corresponding position, that is, the transparency of an object at the corresponding position.
A two-dimensional conversion circuit
202
outputs a two-dimensional image signal that is obtained by mapping the three-dimensional object that has been generated by the rendering circuit
201
to a two-dimensional plane based on view point information that is supplied externally. Where the texture is a moving picture, the above process is executed on a frame-by-frame basis.
With VRML, it is possible to handle, as texture information, data that has been compressed according to JPEG (Joint Photographic Experts Group) which is typically used in high-efficiency coding of a still picture, MPEG (Moving Picture Experts Group) for high-efficiency coding of a moving picture, or the like. Where an image so compressed is used as texture, the texture (image) is decoded by a decoding process corresponding to an encoding scheme. The decoded image is stored in the texture memory
200
a
of the memory group
200
and subjected to a process similar to the above process.
The rendering circuit
201
attaches the texture information that is stored in the texture memory
200
a
to an object at a given position regardless of the format of an image and whether the image is a moving picture or a still picture. Therefore, the texture that can be attached to a certain polygon is stored in one memory. In transmitting three-dimensional object information, it is necessary to transmit three-dimensional coordinates of each vertex. Real number data of 32 bits is needed for each coordinate component. Real number data of 32 bits or more is also needed for such attributes as reflection of each three-dimensional object. Therefore, information to be transmitted is enormous and further increases in transmitting a complex three-dimensional object or a moving picture. Therefore, in transmitting three-dimensional information as above or texture information via a transmission line, it is necessary to transmit compressed information for improving the transmission efficiency.
A typical example of high-efficiency coding (compression) schemes for a moving picture is the MPEG (Moving Picture Experts Group; moving picture coding for storage) scheme, which is discussed in ISO-IEC/JTC1/SC2/WG11 and was proposed as a standard. MPEG employs a hybrid scheme that is a combination of motion-compensation predictive coding and DCT (discrete cosine transform) coding. To accommodate various applications and functions, MPEG defines several profiles (classification of functions) and levels (quantities such as an image size). The most basic item is a main level of a main profile (MP@ML).
An example of configuration of an encoder (image signal coding apparatus) of MP@ML of the MPEG scheme will be described with reference to FIG.
24
. An input image signal is first input to a frame memory
1
, and then coded in a predetermined order. The image data to be coded is input to a motion vector detection circuit (ME)
2
on a macroblock basis. The motion vector detection circuit
2
processes image data of each frame as an I-picture, a P-picture, or a B-picture in accordance with a predetermined
Frommer William S.
Frommer & Lawrence & Haug LLP
Nguyen Phu K.
Polito Bruno
Sony Corporation
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