JPH0346826B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a three-dimensional cursor display circuit for a CRT display device, and in particular to a frame memory.
Memorize the data of each pixel on the CRT screen,
A CRT that reads the contents of frame memory and displays an image on a CRT screen using the raster scan method.
The present invention relates to a three-dimensional cursor display circuit that displays a cursor three-dimensionally in a display device.

Summary of the Invention The present invention controls writing of cursor data to memory in a raster scan type CRT display device by comparing the value of cursor data in the z-axis direction with the value of the displayed image in the z-axis direction. Performs hidden surface processing and displays the cursor in three dimensions.

Prior Art FIG. 3 is a block diagram of a conventional CRT display device. First, with reference to Figure 3, the conventional
A brief explanation of the CRT display device will be given below.
Data is provided from a host computer 1 to a display processor 3 via a communication control circuit 2. The display processor 3 registers data transmitted from the host computer 1. Display processor 3 is host computer 1
Register the data transmitted from. Associated with the display processor 3 are a keyboard 5, a program ROM 6, and a data RAM 7.

The keyboard 5 is used to give commands to display arbitrary data among the data registered in the display processor 3. The program ROM 6 stores programs necessary for the display processor 3 to operate.
The data RAM 7 stores commands and data for display. The data registered in the display processor 3 is given to a high speed calculation circuit 4 for coordinate transformation. This high-speed coordinate conversion calculation circuit 4 calculates the necessary matrix and its data when enlarging, reducing, rotating, or translating the display data (x, y, z) output from the display processor 3. It performs multiplication of , and outputs new data (x', y', z'). The data output from this high-speed calculation circuit for coordinate transformation 4 is given to a clip circuit 8.

When a part of a figure on the CRT display screen is surrounded by a frame, the clipping circuit 8 clips the figure that protrudes from the frame. The output of the clipping circuit 8 is applied to a filling circuit 9 and a straight line generating circuit 10. When filling in a figure, the filling circuit 9 generates line segments by decomposing the coordinates of the origin given from the clip circuit 8 into inner lines, thereby obtaining filling data.
Further, the straight line generation circuit 10 uses the coordinate data of the starting point and the ending point outputted from the clipping circuit 8 to
The intermediate coordinates of the vector connecting the starting point and the ending point are calculated, and the calculation result is sent to the gate circuit 11.
It is developed into the frame memory 12 via the . . .

The frame memory 12 stores each dot on a straight line generated by the straight line generating circuit 10.
The data of each dot stored in the frame memory 12 is provided to a monitor interface 13.
Monitor interface 13 is frame memory 1
The dot data on the dot 2 is read out and applied to the color monitor 14 together with the periodic signal. Color monitor 14
displays a graphic based on data read from the frame memory 12.

FIGS. 4 to 6 are diagrams for explaining hidden surface processing by a conventional CRT display device.

In the CRT display device shown in FIG. 3 described above, the CRT drawing is expressed by a first axis (x-axis) direction and a second axis (y-axis) direction perpendicular to the first axis. It becomes a dimensional plane. A three-dimensional cubic image as shown in FIG. 4 may be displayed on such a two-dimensional CRT screen.
However, in a CRT display device, when new data is given from the display processor 3 to the high-speed coordinate conversion calculation circuit 4, the straight line generation circuit 10 always updates the contents of the frame memory 12, so that the data drawn later is always Graphical data will be displayed with priority. That is, when displaying the image of the cube shown in Figure 4, the inner part of the cube (the shaded part) must be written first to remove hidden surfaces, and if it is written later, the image shown in Figure 5 will be displayed. The shape will look like the one shown in the figure. Also, since last writing is always given priority, when adding a new shape,
Even when processing such as rotation is performed on a displayed figure, it is necessary to newly rearrange all the figure data in the depth direction.
For this reason, it is not suitable for three-dimensionally displaying a relatively complex figure as shown in FIG.

Therefore, in order to display a figure three-dimensionally while performing hidden surface processing, it is known to manage data in the z-axis direction of the figure using a hardware configuration. That is, the respective outputs of the clipping circuit 8 and the filling circuit 9 shown in FIG. 3 are applied to the z-coordinate interpolation circuit 15. The z-coordinate interpolation circuit 15 interpolates the z-coordinate value between the starting point and the ending point based on the coordinate values of the starting point and the ending point in synchronization with the straight line generating circuit 10, and writes the interpolated z-coordinate value in the depth buffer memory 18. The z-coordinate interpolation circuit 15 provides the interpolated z-coordinate value to the comparison circuit 17. On the other hand, depth buffer memory 18
From there, the coordinate value of the coordinate z corresponding to the z coordinate value output from the z coordinate interpolation circuit 15 is read out and given to the comparison circuit 17. The comparison circuit 17 compares the z-coordinate value from the z-coordinate interpolation circuit 15 and the z-coordinate value from the depth buffer memory 18, and determines that the z-coordinate value to be written output from the z-coordinate interpolation circuit 15 has a greater depth. When the z-coordinate value is smaller than the z-coordinate value read from the buffer memory 18, that is, when it is on the near side in the z-direction or coincides with it, the gate circuits 11 and 16 are activated, and the linear generation circuit 1
The image data generated at 0 is stored in the frame memory 12.
z corresponding to the image data.
Write the coordinate values to the depth buffer memory 18.

However, when the z-coordinate value to be written is larger than the z-coordinate read from the depth buffer memory 18, that is, when it is located further in the z-direction, the comparison circuit 17 sends a prohibition signal to the gate circuits 11 and 16. is given to prohibit writing to the frame memory 12 and depth buffer memory 18. Hidden surface processing can be realized by writing this into the frame memory 12 while comparing the z-coordinate values for each pixel.

Problems to be Solved by the Invention FIGS. 7 and 8 are diagrams for explaining a method of displaying a cursor using a conventional CRT display device.

Incidentally, in a CRT display device, a cursor as shown in FIG. 7 may be displayed in order to specify an arbitrary point on the displayed image. When displaying such a cursor, the image data of the cursor is generated by a circuit (not shown) constituted by, for example, RAM, independent of the frame memory 12, and the image data of the cursor is generated by a circuit (not shown) that is independent of the frame memory 12, and is generated by a circuit (not shown) that is independent of the frame memory 12. The image is input to the face 13 and displayed on the color monitor 14. Therefore, even if the image is displayed three-dimensionally, the cursor appears to be floating above the displayed figure, as shown in FIG. Therefore, the conventional
With CRT display devices, even if you can specify any point on the x-axis and y-axis plane with the cursor, you cannot specify any point in the depth direction of the displayed figure, that is, in the z-axis direction. There were flaws.

Therefore, the main object of the present invention is to provide a three-dimensional cursor display circuit for a CRT display device that can display a cursor three-dimensionally while performing hidden surface processing without destroying displayed graphic data. That's true.

Means for Solving the Problems The present invention provides image storage means for storing a plurality of pixel data on a two-dimensional plane in first and second axial directions, and data for each pixel data in a third axial direction. By comparing the value in the depth direction in the depth storage means to be stored and the new graphic data to be written with the data in the third axis direction of each pixel stored in the depth storage means, the image storage means and A CRT display device is provided with a control means for controlling the writing of each data in the depth storage means to perform three-dimensional hidden surface processing. The data in the axial direction and the data in the third axis direction of each pixel stored in the depth storage means are compared by the control means, and based on the comparison result, writing in the cursor storage means is controlled and hidden. Performs surface processing and displays the cursor in three dimensions.

Operation In this invention, the value in the third axis direction of the cursor data stored in the cursor storage means is compared with the data in the third axis direction of each pixel stored in the depth storage means, and the cursor data is When the value of the cursor data in the third axis direction is large, writing of the cursor data to the cursor storage means is prohibited, and when the data of the cursor data in the third axis direction is small, the cursor data is written to the cursor storage means and the cursor data is written to the cursor storage means. , updating of data in the storage areas of the image storage means and depth storage means corresponding to the cursor data is prohibited. Therefore, when specifying an arbitrary point on a three-dimensionally displayed figure with the cursor, you can specify not only an arbitrary point on the two-dimensional plane of the figure, but also an arbitrary point in the third axis direction, that is, the depth direction. .

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention. The embodiment shown in FIG. 1 is the same as the embodiment shown in FIG. 3 above, except for the following points. That is, data for the cursor is generated from the host computer 1 and registered in the display processor 3. The coordinate conversion high-speed calculation circuit 4 outputs new data (x', y', z') for the coordinate data (x, y, z) for the cursor registered in the display processor 3. Furthermore, a gate circuit 20 for performing three-dimensional dragging control,
A dragging plane 22 for storing the z-coordinate value of cursor data generated by the straight line generation circuit 10;
2, and a gate circuit 21 for providing the outputs of the frame memory 12 and dragging plane 22 to the monitor interface 13.
An OR gate 23 is newly provided.

FIG. 2 is a diagram showing a cursor subjected to hidden surface processing according to an embodiment of the present invention.

Next, with reference to FIG. 2, the specific operation of the embodiment of the present invention shown in FIG. 1 will be described. First, in the embodiment of this invention, the cursor's 3
Dimensional display and dragging processing are used together.
That is, the dragging process is a process in which dynamic expression is performed by updating only target graphic data without updating other graphic data.

Coordinate data of the cursor on the x, y plane from the straight line generation circuit 10 is written to the dragging plane 22 via the gate circuit 21, and the z coordinate value of the cursor is written to the comparison circuit via the z coordinate interpolation circuit 15. given to 19. Also, this comparison circuit 1
9, the z coordinate value of the two-dimensional plane image data written in the frame memory 12 from the depth buffer memory 18 is read out and given. Then, the comparison circuit 19 determines which of the z-coordinate value of the cursor and the z-coordinate value of the two-dimensional planar image data is larger. When the z-coordinate value of the cursor is larger than the z-coordinate value of the two-dimensional plane image data, the comparison circuit 19
That is, when it is determined that the cursor is on the back side of the image, the gate circuit 21 is closed and the z-coordinate value of the cursor is prohibited from being written on the dragging plane 22.

However, when the comparison circuit 19 determines that the z-coordinate value of the cursor is smaller than the z-coordinate value of the two-dimensional plane image data, that is, when it determines that the cursor is on the front side of the image, the z-coordinate value of the cursor Write the value to the dragging plane 22. At this time, a three-dimensional dragging control signal is given to the gate circuit 20, and the output of this gate circuit 20 closes the gate circuits 11 and 16.
Writing to frame memory 12 and depth buffer memory 18 is prohibited.

In hidden surface processing mode, if the cursor data is in front of the currently displayed three-dimensional figure, the data written in the frame memory 12 and depth buffer memory 18 is updated. Therefore, when the cursor moves over the displayed figure, the two-dimensional data of the three-dimensional figure that should originally be written to the frame memory 12 and the z-coordinate value of the three-dimensional figure that should be written to the depth buffer memory 18 are Each will be rewritten to the two-dimensional data and z coordinate value of the cursor, so
This is to prohibit these rewrites. and,
The two-dimensional data of the cursor written on the dragging plane 22 or the two-dimensional data of the figure written on the frame memory 12 is given to the monitor interface 13 via the OR gate 23 and displayed on the color monitor 14. Ru.

In this way, when writing cursor data to the dragging plane 22, writing of data to the depth buffer memory 18 and the dragging plane 22 is prohibited.
It becomes possible to perform normal hidden surface processing and hidden surface processing for dragging target figures. Then, as shown in Figure 2, when the cursor is displayed on a three-dimensional figure,
If the cursor is in front of the 3D figure, the entire cursor is displayed, and the 3D figure's z
When specifying an arbitrary point in a direction with a cursor, if the cursor enters a three-dimensional figure, only that part will be erased by hidden surface processing, and only the part that protrudes from the three-dimensional figure will be displayed.

Further, depending on the z-coordinate value of the cursor, it is also possible to read the value in the z-direction of the three-dimensional figure that the cursor is pointing to.

Effects of the Invention As described above, according to the present invention, a cursor storage means for storing cursor data is provided,
The depth direction coordinate value of the cursor data is compared with the depth direction coordinate value of the display shape, and based on the comparison result, the depth direction coordinate value of the cursor is located in front of the depth direction coordinate value of the display shape. When the cursor data is written to the cursor storage means, updating of the data written to the image storage means and the depth storage means is prohibited, and the coordinate value in the depth direction of the cursor is changed to the coordinate value in the depth direction of the image data. Since writing to the cursor storage means is prohibited when the cursor is located further back than the value, the cursor can be displayed three-dimensionally by hidden surface processing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. FIG. 2 is a diagram showing a cursor subjected to hidden surface processing according to an embodiment of the present invention. FIG. 3 is a block diagram of a conventional CRT display device.
FIGS. 4 to 6 are diagrams for explaining hidden surface processing by a conventional CRT display device.
FIGS. 7 and 8 are diagrams for explaining a method of displaying a cursor using a conventional CRT display device. In the figure, 4 is a high-speed calculation circuit for coordinate transformation, 8
is a clip circuit, 9 is a fill circuit, 10 is a straight line generation circuit, 11, 16, 20, 21 are gate circuits, 12 is a frame memory, 13 is a monitor interface, 14 is a color monitor, 15 is a z coordinate interpolation circuit, 18 is a depth buffer memory, 19 is a comparison circuit, 22 is a dragging plane, and 23 is a
An OR gate is shown.

Claims (1)

[Scope of Claims] 1. Image storage means for storing a plurality of pixel data for each pixel on a CRT screen represented by a first axis direction and a second axis direction orthogonal to the first axis direction. and depth storage means for storing, for each of the pixels, a plurality of bits of data in a third axis direction perpendicular to the first and second axes; By comparing the value in the third axis direction with the data in the third axis direction of each pixel stored in the depth storage means, the information is stored in each of the image storage means and the depth storage means. A CRT display device comprising a control means for controlling data writing to perform three-dimensional hidden surface processing, further comprising a cursor storage means for storing cursor data displayed on the CRT screen, the control means for storing cursor data displayed on the CRT screen, The means includes the third data of the cursor data.
and the data in the third axis direction of each pixel stored in the depth means to control writing of the cursor data to the cursor storage means, and A three-dimensional cursor display circuit for a CRT display device, wherein the three-dimensional cursor display circuit performs hidden surface processing on the cursor data and prohibits updating of data in storage areas of the image storage means and the depth storage means corresponding to the cursor data.