JPH09115003A - Z-value coordinate transformation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of data to be stored in a Z buffer RAM without practically lowering the accuracy of depth while considering characters when a main body observes a perspective image. SOLUTION: A Z-value coordinate transformation circuit is connected to a frame buffer control circuit 8 at a polygon control circuit 4. This Z-value coordinate transforming circuit is composed of a shift circuit 2 as a 1st transformation means, Z buffer RAM 1 and shift circuit 3 as a 2nd transforming means. At the shift circuit 2, a Z value is transformed into a non-linear coordinate system, which is expressed and non-linearly divided so as to enlarge the dimension of the coordinate intervals in depth information with the increase of depth, and stored in the Z buffer RAM 1. In the case of write into a frame buffer, the Z value read out of the Z buffer RAM is converted to have an original bit width and a polygon is written into the frame buffer by the frame buffer control circuit 8.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a Z for storing depth information obtained by converting each polygon data into two-dimensional coordinates.
More specifically, the present invention relates to a buffer coordinate conversion circuit, and more particularly to a Z value coordinate conversion circuit that can reduce the amount of data stored in the Z buffer for the depth information.

[0002]

2. Description of the Related Art In computer graphic (CG) image processing, background images and polygons have depth information.
The priority of the polygon is determined. That is, the background image,
It recognizes the front and back of the polygon on the screen and displays the background image and polygon with depth information at the foreground on the screen.

[0003]

The depth information is 2
At the time of dimensional coordinate conversion, it is calculated corresponding to each background image and polygon, stored in the Z buffer, and sent to the frame buffer control circuit for writing the polygon in the frame buffer.
FIG. 6 is a block diagram showing an example of a circuit configuration of a conventional Z buffer. Depth information from the polygon circuit is 19
Expressed in bit width, depth information is stored in the Z buffer RAM for the frame buffer. The depth information is represented by each point obtained by equally dividing the total depth dimension. Z
The contents of the buffer RAM are sent to the frame buffer control circuit of the polygon circuit, the images are combined and sent to the frame buffer.

In the image composition, the precision is more accurate as the depth information is set more finely in order to determine the priority of the display of the background image and each polygon. FIG. 7 shows an example of modeled depth information. The smaller the value of the depth information interval a, the more accurate the accuracy.

By the way, when the subject looks at an object, the context can be accurately recognized when the object is at a short distance, but when the object is at a long distance, the anteroposterior relationship is approximate. I don't feel uncomfortable.
The present invention takes into consideration the characteristics when the subject looks at an image with perspective as described above, and an object of the present invention is to store data stored in the Z buffer RAM without substantially lowering the depth accuracy. It is to provide a Z-value coordinate conversion circuit that can reduce the amount.

[0006]

In order to achieve the above object, a Z-value coordinate conversion circuit according to the present invention temporarily stores depth information obtained by converting each polygon data into two-dimensional coordinates, and writes it in a frame buffer. In the Z buffer circuit for reading the depth information, the depth information of the polygon data expressed in a coordinate system in which the entire depth dimension is equally divided is divided into coordinate systems in which the dimension between the depth information increases as the depth increases. And a Z buffer unit for temporarily storing the depth information converted by the first conversion unit, and the depth information stored in the Z buffer unit. Second conversion means for returning the bit width of the depth information when input to the conversion means. In the above configuration, the bit width of the depth information input to the first conversion means is 19
The bit width of the nonlinear depth information output from the first conversion means may be 16 bits.

According to the above configuration, the amount of data stored in the Z buffer unit can be reduced while maintaining the accuracy of depth information that is the same as the conventional one, and the cost can be reduced. Further, if the amount of data stored in the Z buffer unit is the same as the conventional one, the accuracy of depth information can be further improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall block diagram of a 3D game machine using a Z value coordinate conversion circuit according to the present invention. When a coin is inserted into the coin-related device 14, the coin is transmitted to the CPU 21 via the input / output control device 23, and the game is started. The backup memory 22 stores set values of the number of coins, the number of plays, and the difficulty level. The CPU 21 reads a program for controlling the entire game from the program ROM 16, controls the screen control circuit 25 and the polygon control circuit 4 in accordance with the read program, and displays the initial screen on the CRT 12. Work RAM 17 is CP
This is an area used when U21 performs a calculation.

The communication RAM 18 stores a command of the CPU 21 regarding sound.
21 is used when confirming the sound condition. Sound is generated by the sound system circuit 19 and output from the speaker 20. The screen control circuit 25 specifies a background image such as a landscape to be displayed from the three-dimensional coordinates of the player, and the screen character ROM 24 connected to the screen control circuit 25 is a character (16 × 16 dots) forming the background image. Is stored, and the character at the address read from the screen memory 26 is read. The polygon data read from the polygon data memory 9 is three-dimensionally processed by the polygon control circuit 4, converted into two-dimensional data, and stored in the frame buffer 11. The contents of the frame buffer 11 pass through the polygon control circuit 4 and the color RAM / D / A
The converter 10 converts the analog RGB signal into a CRT1.
2 is displayed.

FIG. 2 is a block diagram showing an embodiment of the Z value coordinate conversion circuit according to the present invention. The polygon control circuit 4 receives the three-dimensional coordinates representing the reference points (vertices) of the three-dimensional model displayed in the world coordinate system and the vertex coordinates of the polygons forming the three-dimensional model. The three-dimensional arithmetic circuit 5 converts the three-dimensional coordinates represented by the world coordinate system into a player coordinate system having the player as the origin. The perspective conversion circuit 6 uses three polygons that form a three-dimensional model.
The dimensional coordinates are converted into two-dimensional coordinates on the CRT.

The clipping circuit 7 checks whether or not the perspective-transformed polygon falls within the display range of the CRT, and if the polygon is outside the CRT, the intersection of the polygon and the CRT is used as the vertex coordinates. In the frame buffer control circuit 8, so-called rendering processing is performed, and each polygon is written in the frame buffer based on the Z value from the Z value coordinate conversion circuit. The Z-value coordinate conversion circuit is connected to the frame buffer control circuit 8 and is the shift circuit 2 which is the first conversion means.
And a Z-buffer RAM 1 and a shift circuit 3 which is a second conversion means.

The Z value calculated by converting the three-dimensional coordinates of each polygon into the two-dimensional coordinates on the CRT by the perspective conversion circuit 6 is input to the shift circuit 2 as depth information having a 19-bit width. This Z value is depth information in a coordinate system obtained by dividing the entire depth dimension at equal intervals, and the shift circuit 2 performs conversion for expressing it in a coordinate system that is nonlinearly associated with a 16-bit width. To do. FIG. 3 shows the shift circuit 2
6 is a diagram for explaining a coordinate system conversion method in FIG. A coordinate system P (Z axis shown by a dotted line) is a coordinate system in which the entire depth dimension is equally divided, and the Z value of the polygon represented by the coordinate system P is input to the shift circuit 2. The shift circuit 2 converts the coordinate system P into a Z value when the coordinate system T is set. The coordinate system T is a non-linear coordinate system that is non-linearly divided and is divided and expressed such that the dimension of the coordinate interval of the depth information increases as the depth increases.

Therefore, the depth position P ₁ in the coordinate system P is associated with T ₁ in the coordinate system T. The depth positions P ₂ and P ₃ in the coordinate system P are associated with T _{2 of the} coordinate system T, and the depth position P ₄ is associated with T ₄ . When the depth position is far, the player cannot accurately distinguish the front-back relationship even if the dimension of the depth coordinate interval is increased. Therefore, for example, the position of the polygon is set to the coordinate system T.
Converting to T ₄ does not change the substantial accuracy.
Table 1 is a diagram showing an example of a conversion table of depth information in the coordinate system P and non-linear depth information in the coordinate system T. (Hereafter referred to as margins.)

[Table 1] In Table 1, for example, the interval of 0 to 7FFFh in the coordinate system P is 0 to 7FFFh in the coordinate system T as well, and the change amount does not change at a ratio of 1: 1 in the range of close distance.
The interval of 8000h to FFFFh in the next coordinate system P is 8000h to BFFFh in the coordinate system T, and the change amount is 1:
2 and the change amount of the coordinate system T is doubled. Further, the interval of 10000h to 17FFFh of the coordinate system P is C000h to DFFFh of the coordinate system T, the change amount is 1: 4, and the change amount of the coordinate system T is four times. This gives 19
The information amount of the bit width can be expressed by the 16-bit width. The depth information converted in this way is stored in the Z buffer RAM 1.

FIG. 4 shows the Z stored in the Z buffer RAM.
It is a figure which shows an example of a value. In the Z buffer RAM ₁ , the Z value T ₁ of the vertex coordinates of the polygon for each polygon number,
_{T 2, T 4, T 5} (16 -bit width) are stored. When writing to the frame buffer, the Z buffer RA
The Z value stored in M1 is read out, and the depth information represented by 16 bits is associated with the coordinates (19-bit width) of the coordinate system P obtained by equally dividing the total depth dimension by the shift circuit 3. For example, in FIG. 3, the depth position P ₁ input to the polygon shift circuit 2 is associated with T ₁ of the coordinate system T by the shift circuit 2, and further associated with P ₁ ′ of the coordinate system P by the shift circuit 3. That is, coordinate system T
As a result of the conversion, the depth position of P _{1 in} the coordinate system P is increased by two scales and moved to the position of P ₁ ′, but since it is a depth position with a considerable distance, the depth accuracy seen from the player is Does not matter.

FIG. 5 is a diagram for explaining writing to the frame buffer based on the Z value of the Z buffer RAM. The polygon image data is written in the frame buffer based on the Z value of the polygon written in the Z buffer RAM. Next, the Z value of the polygon is the Z buffer R
AM is written. The frame buffer control circuit 8 writes in the frame buffer based on the priority of polygons and polygons. In FIG. 5, the polygon is written after the polygon. Further, the Z value of the polygon is written in the Z buffer RAM. The frame buffer control circuit 8 writes in the frame buffer based on the priority of polygons. The polygon is written before the polygon.

[0016]

As described above, according to the present invention, the amount of information stored in the Z buffer portion can be reduced while maintaining the accuracy of depth information that is the same as the conventional one, so that a Z buffer RAM having a smaller capacity than the conventional one is used. Can contribute to cost reduction. Further, if the amount of data stored in the Z buffer unit is the same as the conventional one, the accuracy of depth information can be further improved.

[Brief description of the drawings]

FIG. 1 is an overall block diagram of a 3D game machine using a Z-value coordinate conversion circuit according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a Z-value coordinate conversion circuit according to the present invention.

FIG. 3 is a diagram for explaining a coordinate system conversion method in a shift circuit.

FIG. 4 is a diagram showing an example of Z values stored in a Z buffer RAM.

FIG. 5 is a diagram for explaining writing to a frame buffer based on a Z value of a Z buffer RAM.

FIG. 6 is a circuit block diagram showing an example of a conventional Z buffer RAM.

FIG. 7 is a diagram for explaining a conventional method of expressing depth information.

[Explanation of symbols]

 1 ... Z buffer RAM 2 ... Shift circuit 3 ... Shift circuit 4 ... Polygon control circuit 5 ... Three-dimensional arithmetic circuit 6 ... Perspective conversion circuit 7 ... Clipping circuit 8 ... Frame buffer control circuit 10 ... Color RAM / D / A converter 11 ... Frame buffer 12 ... CRT 13 ... RS-232C 14 ... Coin-related device 15 ... Operating device 16 ... Program ROM 17 ... Work RAM 18 ... Communication RAM 19 ... Sound system circuit 20 ... Speaker 21 ... CPU 22 ... Backup memory 23 ... Input Output control device 24 ... Screen character ROM 25 ... Screen control circuit 26 ... Screen memory

Claims (2)

[Claims] 1. A Z-buffer circuit that temporarily stores depth information obtained by converting each polygon data into two-dimensional coordinates and reads the depth information when writing to a frame buffer, in a coordinate system in which all depth dimensions are equally divided. A first conversion unit for converting the depth information of the represented polygon data so as to be expressed by a coordinate system divided such that the dimension between the depth information increases as the depth increases; and the first conversion unit. The Z buffer unit for temporarily storing the converted depth information, and the depth information stored in the Z buffer unit are stored in the first buffer unit.
The second conversion means for returning the bit width of the depth information when input to the conversion means, and the Z-value coordinate conversion circuit. 2. The bit width of the depth information input to the first conversion means is 19 bits, and the bit width of the nonlinear depth information output from the first conversion means is 16 bits. The described Z value coordinate conversion circuit.