JPH02171971A - Three-dimensional graphic display device - Google Patents

Abstract

PURPOSE:To rapidly execute processing for clipping a three-dimensional graphic and displaying it on a screen by a simple constitution by previously setting up Z coordinate values most close to a visual point on respective areas of a Z buffer corresponding to the X and Y coordinate positions of respective picture elements in the outside area of a clipping boundary. CONSTITUTION:The X and Y coordinates (indicate the addresses of the Z buffer 11) of all points in the outside of a clipping area applied from a processor 13 are generated based on the boundary information of the area and a clipping boundary setting part 15 for writing a Z value (e.g. 0) arranged so that the z position is most close to your side on its corresponding position of the Z buffer 11 is formed. Since all the graphic parts on the outside of the clipping boundary out of respective plane graphics in a three-dimensional space approximating a three-dimensional object are separated far from the visual point as compared with the value of the corresponding areas in the specified Z buffer, the graphic parts are not written in a frame buffer 12 by hidden surface processing based on Z buffer algorithm and clipped as the result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a three-dimensional figure display device suitable for clipping and displaying three-dimensional figures.

(Prior art) In general, the process of displaying a three-dimensional object (three-dimensional figure) on a display monitor using the Rusk scan method is basically: ■ A three-dimensional object is expressed by three-dimensional coordinates of X, Y, and Z A process of approximation using a set of surface figures (for example, triangles) in three-dimensional space,
■X on the surface figure.

The color intensity of each pixel position specified by the Y coordinate value and the Z coordinate value (
This is realized by a process of calculating a depth direction coordinate value) and a process of filling each surface figure by so-called shading (glow shading, smooth shading) using the process result of (2) above. This filling process (■) is performed on the three-dimensional graphic display device shown in FIG.
Z buffer (Z
buffer memory) 21, and a frame buffer (frame buffer memory) 2 that stores information on screen display figures as an array of color intensities for each pixel position (X, Y coordinate values).
2, as follows.

First, the x, y, and z coordinate values and color intensity (luminance) of each pixel on the surface figure to be filled are provided pixel by pixel by the processor 23 to the hidden surface processing unit 24 that performs hidden surface processing to be described later. The hidden surface processing unit 24 calculates the Z coordinate value (new binary) of the pixel (pixel position) given by the processor 23 and the Z coordinate value in the Z buffer y21 corresponding to the X and Y coordinate values of the same pixel.
Compare the size with the coordinate value (old Z value). Through this comparison, for example, if it is determined that the new Z value is earlier than the old Z value, the hidden surface processing unit 24 updates the old Z value in the Z buffer 21 to the new Z value, and at the same time buffer 22
The color intensity (Japanese-French intensity) at the position corresponding to the X, Y coordinate values in the area is updated to the color intensity (new color intensity) at the pixel position on the figure to be filled in indicated by the X, Y coordinate values. On the other hand, if it is determined that the new Z value is further back than the old Z value, the hidden surface processing unit 24 does not perform the above update,
Therefore, the old Z value and the Japanese and French intensities in the frame buffer 22 are preserved. This is the so-called hidden surface processing,
The above update algorithm is called the Z-buffer algorithm. After repeating the above operations for all pixels (pixel positions) of each surface figure that approximates a three-dimensional object, the contents of the frame buffer 22 are displayed on the screen, making it possible to display the three-dimensional figure by smooth shading. In addition,
If the surface figure to be filled is a triangle, the x, y, z coordinate values and color intensity of its vertices are processed by the processor 23.
(host device) to the hidden surface processing section 24, the hidden surface processing section 24 receives the X of each pixel on the surface figure,
It is also known to generate Y and Z coordinate values and color intensity (luminance) (eg, Japanese Patent Application No. 308622/1982).

Now, in a three-dimensional graphic display device, there are cases where it is required to display the three-dimensional object to be displayed only within the area of the display screen, rather than displaying the three-dimensional object as it is on the screen using the above procedure. At this time, it is necessary to remove the graphic portion that protrudes from the L area. Such processing is called clipping processing. Conventionally, clipping processing of a three-dimensional figure has been performed as follows by a clipping processing section 25 provided between a hidden surface processing section 24 and a frame buffer 22, as shown in FIG. That is, first, the processor 23 supplies the clipping processing unit 25 with boundary information indicating the boundary of the area (clipping area). When the hidden surface processing unit 24 attempts to update the color intensity of the frame buffer 22, the clipping processing unit 25 checks whether the target X and Y coordinates are within the clipping area specified by the processor 23 and If so, clipping processing is performed by prohibiting the above update.

(Problems to be Solved by the Invention) As described above, in the conventional three-dimensional graphic display device, there is a hidden surface processing section that performs hidden surface processing, and writing to the frame buffer is determined by the hidden surface processing of this hidden surface processing section. If the update target Therefore, there were problems in that the configuration became complicated and the graphic display speed decreased.

Therefore, the problem to be solved by the present invention is to enable the process of clipping a three-dimensional figure and displaying it on a screen to be performed at high speed with a simple configuration.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a three-dimensional graphic display device equipped with hidden surface processing means that performs hidden surface processing according to a Z-buffer algorithm. The present invention is characterized in that means is provided for presetting a predetermined Z coordinate value indicating the farthest Z position from the viewpoint in each area of the Z buffer corresponding to the X and Y coordinate positions.

(Function) According to the above configuration, a predetermined Z coordinate value indicating the farthest Z position from the viewpoint is set in advance in each area of the Z buffer corresponding to the X and Y coordinate position of each pixel in the area outside the clipping boundary. Therefore, out of each surface figure in the three-dimensional space that approximates the three-dimensional object, all the figure parts that are outside the clipping boundary are farther from the viewpoint than the value of the corresponding area in the Z buffer set above. Therefore, it is not written to the frame buffer due to hidden surface processing according to the Z-buffer algorithm, and as a result, it is clipped.

(Embodiment) FIG. 1 is a block diagram of a three-dimensional graphic display device according to an embodiment of the present invention. In the figure, reference numeral 11 indicates information on a screen display figure corresponding to a three-dimensional object at each pixel position (X,
A Z buffer 12 stores information on the screen display figure as an array of Z coordinate values for each pixel position (Y coordinate value).
This is a frame buffer that stores color intensities as an array for (X, Y coordinate values). 13 is a processor that controls the entire device; 14 is an X of each pixel position (coordinate point) of each surface figure that approximates a three-dimensional object given by the processor 13;

A hidden surface processing unit 16 performs hidden surface processing according to a buffer algorithm based on Y and Z coordinate values and color intensities, and a hidden surface processing unit 16 processes all points outside the clipping region based on the boundary information of the clipping region given from the processor 13. X, Y coordinates (Z indicating
The address of buffer 11) is generated, and the Z value (in this case, 0
) is a clipping boundary setting section that writes. It should be noted that the apparatus of FIG. 1 is not provided with a processing block corresponding to the clipping processing section 25 of FIG. 2.

Next, the operation of the configuration shown in FIG. 1 will be explained.

First, when displaying a three-dimensional figure, initialization processing is performed to write a binary value (for example, the maximum value of Z) indicating the farthest Z position from the viewpoint into each area of the Z buffer 11, and to clear all areas of the frame buffer 12 to zero. It will be done. Next, if the three-dimensional figure needs to be clipped, clipping boundary information indicating the boundary of the clipping area is provided from the processor 13 to the clipping boundary setting unit 15. Upon receiving the clipping boundary information from the processor 13, the clipping boundary setting unit 15 sets the X and Y coordinate positions (addresses) of all points in the area outside the clipping boundary indicated by the information.
are generated in sequence, and the Z buffer 11 corresponding to the coordinate position is
Z value (for example, 0) indicating the Z position closest to the viewpoint in the area
I will write in.

When the above processing is completed, the processor 13 calculates the X, Y, Z coordinate values and color intensity (luminance) of each pixel on each surface figure for each surface figure that approximates the target three-dimensional object, pixel by pixel. It is given to the hidden surface processing section 14.

Note that it is also possible to generate the x, y, and z coordinate values and color intensity (luminance) of each pixel on the surface figure in the hidden surface processing section 14.

The hidden surface processing section 14 performs hidden surface processing on each pixel on the surface figure according to the two-buffer algorithm, similar to the hidden surface processing section 24 described in the conventional example. That is, the hidden surface processing unit 14
The Z coordinate value (new Z value) of the target pixel is compared with the Z coordinate value (old Z value) in the Z buffer 21 corresponding to the X and Y coordinate values of the same pixel. This comparison shows that the new ZtB is better than the old Z.
If it is determined that the Z position corresponding to the new Z value is smaller than the Z position corresponding to the old Z value, the hidden surface processing unit 14
The value is updated to the new Z value, and at the same time, the color intensity (Japanese and French intensity) of the position corresponding to the -L x and Y coordinate values in the frame buffer 22 is updated to the F plane figure indicated by the X and Y coordinate values. Update to the color intensity of the upper pixel position (new color intensity).

On the other hand, the new 2-value is larger than the old Z-value, so the 2-position corresponding to the new Z-value is better than the Z-position corresponding to the old ZEM.
If it is determined that the hidden surface processing unit 14 is further back than the position, the hidden surface processing unit 14 does not perform the above update, and therefore the old Z value and the Japanese and French intensities in the frame buffer 22 are saved.

Now, in this embodiment, the Z value of fnO is written in advance in the Z buffer 11 corresponding to each pixel position in the area outside the clipping boundary, as described above.

Therefore, in the hidden surface processing according to the Z algorithm by the hidden surface processing unit 14 described above, for pixels outside the crimping area, the new Z value is determined to be larger than the old Z value, which is all 0, and the above update is performed. Not done. Therefore, the intensity of one color (value 0) in the area of the frame buffer 12 (the old Z value in the area of the Z buffer 11 and the value 0) corresponding to each pixel outside the clipping area is always saved, and the intensity of one color (value 0) in the area in the frame buffer 12 is always saved. Color intensity is never written. That is, according to this embodiment, the well-known hidden surface processing according to the Z-buffer algorithm is performed by the hidden surface processing section 14, so that the processor 23 can be used without using the ripping processing section, as shown by reference numeral 25 in FIG. You can clip 3D shapes with specified clipping boundaries.

[Effects of the Invention] As detailed above, according to the present invention, surface figures outside the clipping boundary can be clipped by hidden surface processing according to the Z-buffer algorithm, so it is possible to clip three-dimensional figures. Screen display processing can be performed at high speed without using a special clipping circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a three-dimensional graphic display device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional three-dimensional graphic display device. 11...Z buffer, 12...frame buffer,
I3... Processor, 14... Hidden surface processing unit, 15.
... Clipping boundary setting section. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A three-dimensional figure display device that approximates a three-dimensional object with a plurality of surface figures in a three-dimensional space expressed by three-dimensional coordinates of X, Y, and Z, and displays each surface figure on a screen by filling it in. , there is a Z buffer for storing the information of the screen display figure as an array of Z coordinate values for each pixel's X, Y coordinate position, and a Z buffer for storing the information of the screen display figure as an array of the color intensity for each pixel's X, Y coordinate position. A frame buffer for storing as an array and a predetermined Z coordinate value indicating the farthest Z position from the viewpoint are set in advance in each area of the Z buffer corresponding to the X and Y coordinate position of each pixel in the area outside the clipping boundary. and the Z coordinate values of the X and Y coordinate positions of each pixel of each surface figure and the setting values of the area of the Z buffer corresponding to the same X and Y coordinate positions, and according to the comparison result, the same hidden surface processing means for updating setting values of both areas of the Z buffer and the frame buffer corresponding to the X and Y coordinate positions, and an area in the Z buffer where the predetermined Z coordinate value is set. and an area in the frame buffer corresponding to the same area is not updated by the hidden surface processing means.