JPH01244585A - Graphic data clipping processing system - Google Patents

Abstract

PURPOSE:To easily and promptly execute a graphic data clipping processing with an arbitrary polygon by executing the clipping processing with the free polygon by means of a depth buffer memory. CONSTITUTION:A depth buffer memory 8 is initialized by a minimum value, next, a 'forcible writing mode' is set, and a maximum value is written into the area of the depth buffer memory 8 corresponding to the inside of an arbitrary clipping polygon CP to internally display the graphic. At such a time, the maximum value is outputted by a straight line generator 7 as Zc33. Next, the depth buffer memory 8 is set at a normal 'comparative writing mode', and the comparison of a coordinate value Z outputs a writing signal 37/52 of the data depth buffer memory/a frame buffer memory 8/9 at the time of Zc<Z, and the data are updated. Thus, the graphic data outside the clipping polygon CP initialized by the minimum value are not written into the frame buffer memory 9, and the clipping processing by the arbitrary polygon can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a graphic data clip processing method using free polygons for a three-dimensional graphic display device.

[Conventional technology]

FIG. 4 shows a block diagram of an example of a conventional ripple scan type three-dimensional graphic display device of this type that performs hidden surface processing using a depth buffer memory.

In the figure, 1 is an interface signal with a computer (not shown), 2 is an interface circuit, and 3 is a control device for converting display data, display commands, etc. sent from the computer through the interface circuit 2 into an internal format. , 4 is a storage circuit for storing the display data, display commands, etc. converted into an internal format. The data stored in the storage circuit 4 is manually input to the straight line generator 7 via the coordinate conversion circuit 5 and the clip processing circuit 6 based on instructions from the control device 3. Further, 8 is a depth buffer memory, 9 is a frame buffer memory, 10 is an interface circuit for a display CRT (cathode ray tube) 11, and 12 is an input device to the control device 3.

Conventional clip processing by the clip processing circuit 6 (°
``Cripping'' is described, for example, in the literature ``Graphic processing engineering using computer displays'' (written by Fujio Yamaguchi, published by Nikkan Kogyo Shimbun on January 25, 1988), No. 138-
As shown in the description of "Two-dimensional clipper" on page 144, the X coordinate.

Since it was configured to make decisions based on the upper and lower limits of the Y coordinate, the display was always a rectangular area.

In the case of three-dimensional clipping, the processing is more complicated, but the display is a rectangular area, which is the same as in the case of two-dimensional clipping.

FIG. 5 is a detailed block diagram of the depth buffer memory 8 used to execute the hidden surface processing algorithm, and numerals 1 to 12 indicate the same or equivalent components as in FIG. 4, respectively. 31°32.33 is that-rh
The coordinate data 31 is X in each coordinate data generated by the straight line generator 7 in the x-y-z three-dimensional coordinate system. , the coordinate data 32 is Yc, and the coordinate data 33 is zc. 34 is a strobe signal for sampling and linking each coordinate data 31, 32, and 33. 35 is the Z coordinate data value Z read out from the depth buffer memory 8, and 36 is the Z coordinate (
The irf comparator compares each coordinate data Z633 and 235 and outputs an output 37. This output 37 is Zc≦Z
The flag signal becomes a write flag for the depth buffer memory 8 and a write flag for the frame buffer memory 9.

Next, the operation will be explained. The straight line generator 7 sequentially generates coordinate data from the start point to the end point based on the start point coordinate data (Xs, Ys, Zs) and the end point data (XE, YE, Zr:), and applies the hidden surface processing algorithm to the coordinate data. It is given to the depth buffer memory 8 for execution. The depth buffer memory 8 reads the coordinate data Z35 from the depth buffer memory position addressed by the coordinate data xc31 and YC32 among the coordinate data (xc, yc, zc) generated by the linear generator 7, and when zC≦2 , coordinate data Z. 33 to that memory location, and provides coordinate data Xc, YC and an update flag 37 indicating that the depth buffer memory 8 has been updated to the frame buffer memory 9. Note that if the depth buffer memory 8 is not updated, the coordinate data and update flag are not manually stored in the frame buffer memory 9.

When the frame buffer memory 9 receives the soil update flak, the frame buffer memory 9 receives the coordinate data X. , YC, the display information such as the brightness or color that has been set Pth is written to the position of the frame buffer memory 9 addressed by YC. The data written in the frame buffer memory 9 is read out according to the display address generated by the CRT interface circuit 10, and is sequentially sent to the CRT 11 for display.

Further, the configuration was such that data could be given to the control device 3 by the human-powered device 12 as needed.

[Problem to be solved by the invention]

However, conventional graphic display devices of this type are
Because it was configured as follows, it could only process clipping of rectangular areas, and clipping of graphic data using arbitrary polygons depended on a special algorithm and required a long processing time.

This invention was made in order to solve the problems of the prior art as described below. 1) Providing a means for easily and quickly clipping graphic data using arbitrary polygons. It is an object.

[Means to solve the problem]

Therefore, in the graphic display device according to the present invention, for example, it is possible to control the initialization value for the depth buffer memory, and also to provide a mode in which data is forcibly written while ignoring the Z [standard value comparison]. By configuring the present invention to be able to perform graphic data clipping processing in an arbitrary polygonal shape, the object 1 is attempted to be achieved.

(Operation) With the above configuration, it is possible to clip graphic data using a frame of an arbitrary shape in this type of three-dimensional graphic display device.

〔Example〕

The present invention will be explained below based on Examples.

FIG. 1 shows a raster scan type 3 of this type according to the present invention.
FIG. 1 shows a block diagram of an embodiment of a dimensional graphic display device.

(Structure) In the drawings, reference numerals 1 to 12 and 31 to 37 respectively indicate the same or equivalent components as in the conventional device shown in FIG. 4.5, and redundant explanation will be omitted. 50 is a forced write flag for outputting an instruction signal 51 for forcibly writing to the depth buffer memory 8, and is set by means not shown.

52 is a write flag for the frame buffer memory 9, which is controlled independently of the write flag 37 for the depth buffer memory 8.

In the "forced write mode", the coordinate data Zc33 output from the linear generator 7 is the address coordinate data X.3.
1. The configuration is such that the data is forcibly written into the depth buffer memory 8 according to Yc32.

(Processing flow) To summarize, the process flow is as follows.

(See FIG. 2, an explanatory diagram of each area of the depth buffer memory 8.) 1. First, the depth buffer memory 8 is initialized to the minimum value (area A).

2. Set the "forced write mode" and write the maximum value to the area of the depth buffer memory 8 that corresponds to any clipping polygon that displays graphics inside (-as an example, the clipping polygon cp B area).At this time, the maximum value is output from the linear generator 7 as Zc33.

(FIG. 2) At this time, a write signal may be output to the frame buffer memory 9 to paint the corresponding area with a specified background color.

3. Set the depth buffer memory 8 to the normal "comparison write mode" and perform graphic data display processing.

At this time, the minimum rectangular area surrounding the clipping polygon CP is set in the clip processing circuit 6, and line segments that do not require processing are removed in advance.

When comparing the coordinate values Z, only when ZC<Z, a write signal 37152 for the depth buffer memory/frame buffer memory 8/9 is output to update the data. the result,
Graphic data outside the clip polygon CP initialized with the minimum value is not written to the frame buffer memory 9, and clip processing using arbitrary polygons is realized.

FIG. 3 shows that, as a specific example of FIG. 2, on the country side where the dice D are displayed, the dashed line portion is clipped and only the clipping polygon C is displayed.

〔Effect of the invention〕

As described above, according to the present invention, it has become possible to easily and quickly perform clipping processing of graphic data by clipping patterns of arbitrary shapes in a three-dimensional graphic display device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the graphic display device according to the present invention, FIG. 2 is an explanatory diagram of each area of the depth buffer memory in FIG. 1, and FIG. On the national side, FIG. 4 is a block diagram of an example of a conventional graphic display device.
FIG. 5 is a detailed block diagram of the depth buffer memory shown in FIG. 4. 8... Depth buffer memory 11... CRT CP... Clipping polygon Note that in each figure, the same reference numerals represent the same or equivalent components.

Claims (1)

[Claims] A raster scan type three-dimensional graphic display device that is equipped with a depth buffer memory and performs hidden surface/line processing, wherein the depth buffer memory is used to perform clip processing using free polygons. method.