Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2000-06-23
2003-02-18
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
Reexamination Certificate
active
06522337
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method, and a recording medium storing a program for causing this image processing method to be implemented in a computer, and more particularly, it relates to an image processing apparatus, image processing method and storage medium, whereby images can be displayed without significant distortion, even in cases where updating of texture data in a particular scene is not completed in time.
2. Description of the Related Art
A game apparatus or simulation apparatus generates and displays images corresponding to the progress of a game, or the like, by executing a game program or simulation program in response to operational inputs made by an operator. For this purpose, it comprises an integral image processing apparatus and display apparatus.
The image processing apparatus comprises a geometry processing unit, rendering unit, texture processing unit, frame buffer and digital/analogue (D/A) converting unit, and the like. The geometry processing unit performs co-ordinate conversion of polygon data constituting objects. More specifically, firstly, the geometry processing unit converts polygon data from an object co-ordinates system (local co-ordinates system defining object) to a global co-ordinates system (co-ordinates system wherein objects have positional relationships). Thereupon, the geometry processing unit converts polygon data from a three-dimensional (3D) global co-ordinates system to a two-dimensional (2D) screen co-ordinates system (co-ordinates system defined on a screen). In other words, the geometry processing unit carries out perspective processing.
The rendering unit converts polygon data that has been converted to the screen co-ordinates system into image data in pixel units. The texture processing unit has a texture memory storing texture data (colours, patterns, and the like, of the surfaces of objects), and it performs texture mapping.
The image data in pixel units generated by the rendering unit is stored in the frame buffer. The digital/analogue converting unit converts the digital-format image data in pixel units stored in the frame buffer into an analogue signal, which is supplied to the display apparatus, where images are displayed.
When displaying images, high speed is required in the rendering process. Consequently, it is also necessary to access the texture memory at high speed. In general, in order to perform high-speed access, it is desirable to use an SRAM (Static Random Access Memory) as a texture memory, but compared to a DRAM (Dynamic Random Access Memory), or the like, an SRAM involves extremely high cost per unit bit (high cost with respect to capacity).
On the other hand, in order to make the displayed images more realistic, it is necessary to use more texture data, and in cases where a DRAM is used for the texture memory, due to the requirement for high-speed access to the aforementioned texture memory and the requirement of low cost of the texture memory, it is difficult to enlarge capacity very greatly.
Therefore, the required texture data is stored in an external memory (hard disk, or the like) separate from the texture memory. By providing a time period during which no drawing is performed at times when the scene of the displayed image changes and by rewriting the texture data in a portion or the whole of the texture memory during this time period, it is apparently possible to handle a large amount of texture data.
FIGS. 1A-1E
illustrate modes of storing MIPMAP texture data.
FIGS. 1A-1E
show, for example, texture data having five levels of detail (hereinafter, called LOD, for the sake of convenience). The horizontal axis is the x axis and the vertical axis is the y axis.
FIG. 1A
shows texture data having LOD=0, which is the highest level of detail. This data has the highest image resolution, and the size of the x axis in this data area is Size X, whilst the size of the y axis is Size Y.
FIG. 1B
shows texture data having the next level of detail LOD=1;
FIG. 1C
shows texture data having the next level of detail LOD=2;
FIG. 1D
shows texture data having the fourth level of detail LOD=3; and
FIG. 1E
shows texture data having the lowest level of detail LOD=4. The texture data for LOD=1 to LOD=4 is derived by reducing the texture data for LOD=0. In other words, if the LOD value of the texture data rises to 1, then the x axis and y axis are reduced to ½ (surface area to ¼).
Therefore, the higher the level of detail, the lower the LOD value and the greater the amount of data, whereas the lower the level of detail, the higher the LOD value and the smaller the amount of data. Texture data of differing levels of detail, from LOD=0 to LOD=4, is used according to the size displayed on the screen. In other words, image processing is optimized in such a manner that, if the size displayed on the screen is large, then texture data of a higher level of detail is used, and if the size displayed on the screen is small, then texture data of a lower level of detail is used.
FIGS. 2A-2E
show a example of a method for updating MIPMAP texture data as shown in
FIGS. 1A-1E
. In the example in
FIGS. 2A-2E
, the updating (rewriting) process is carried out in sequence, starting from the texture data of the highest level of detail (LOD=0).
FIG. 2A
shows texture data
0
having LOD=0, which is the highest level of detail,
FIG. 2B
shows texture data
1
having LOD=1,
FIG. 2C
shows texture data
2
having LOD=2,
FIG. 2D
shows texture data
3
having LOD=3, and
FIG. 2E
shows texture data
4
having LOD=4, which is the lowest level of detail.
The texture data
0
having the highest level of detail has the largest volume of data, and therefore it has the longest updating time, but the image displayed thereby is the most clear. Thereupon, as the updating process proceeds through texture data
1
, texture data
2
, texture data
3
, texture data
4
, the volume of data becomes smaller and the data volume of texture data
4
is the smallest. Consequently, texture data
4
having the lowest level of detail has the shortest updating time period, but the image displayed thereby is the least distinct.
Here, the area of the texture data
0
where the texture data has been updated is taken as the updated texture data area
11
indicated by the diagonal lines, and the area where texture data has not yet been updated is taken as the non-updated texture data area
12
. In this case, the data at texel
21
, a texel being the picture element unit for texture data, is data for which updating has been completed, but the data at texel
22
is data which has not been updated. Therefore, since the displayed image contains a mixture of updated texture data and non-updated texture data, the image will be distorted. However, since this occurrence is undesirable, usually, texture data is used in image processing for a new scene only after it has been confirmed that updating for all texture data from texture data
0
to
4
has been completed.
Nevertheless, in cases where scenes change rapidly with the passage of time, such as in game apparatuses, there has been a problem in that the fact of having to wait for updating of MIPMAP-format texture data to be completed has interrupted the flow of scenes.
Moreover, although it is possible to regulate the volume of texture data to a smaller data volume, in order that texture data can be updated within a prescribed period of time in such a manner that the flow of scenes is not interrupted, in this case, a problem arises in that insufficient usable texture data can be created.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an image processing apparatus whereby distortion of displayed images can be suppressed, as far as possible, in cases where updating of texture data is not completed in time when displaying a prescribed scene.
In order
Dickstein , Shapiro, Morin & Oshinsky, LLP
Sega Enterprises Ltd.
Vo Cliff N.
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