JPH09305792A - Hidden surface processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely perform the hidden surface processing by selecting successively the objects at the forward side of a visual point in a prescribed range based on the Z coordinate value representing every object and forming a display image based on the Z coordinate value of every image. SOLUTION: A Z sort processing circuit 3 decreases the processing objects and also performs the hidden surface processing to the rectangular areas which are successively inputted at the forward side of a visual point by a Z buffer method. Under such conditions, the rectangular areas which are not necessary for display are excluded from the processing objects in the circuit 3. Accordingly, the access frequency of memory interface 6 is reduced to a display buffer 7 and a Z buffer 8. At the same time, the vertex data on the rectangular areas are successively outputted at the forward side of the visual point. As a result, the image data are stored in the buffer 7 in the order of higher possibility of display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hidden surface processing method, which is applied to, for example, a graphics drawing device, and a Z coordinate value representing each object is used as a reference in a predetermined range in front of a viewpoint. Side by side select objects,
By forming the display image based on the Z coordinate value of each pixel, the hidden surface processing can be performed easily and reliably.

[0002]

2. Description of the Related Art Conventionally, in a graphics drawing device, a three-dimensional object represented by, for example, a polygon is displayed by a hidden surface process by the so-called Z sort method or Z buffer method.

That is, in the case of processing a plurality of polygons in a graphics drawing apparatus using the Z sort method, the plurality of polygons are sorted based on the Z coordinate value of a representative point representing each polygon, and the polygons are sorted with respect to the viewpoint. The contents of the display buffer are sequentially updated from the polygon located at the back. As a result, the graphics drawing device by the Z sort method sequentially draws the image on the front side from the image displayed in the back to form a display image.

That is, as shown in FIG. 2, a rectangular shape,
When arranging circular-shaped and triangular-shaped polygons P1, P2, and P3 in order from the back, in the graphics drawing device of the Z sort method, first, the rectangular-shaped polygon P
1 is selected and the image data of this polygon P1 is stored in the display buffer (FIG. 2 (A)). Then, a circular polygon P2 located in front of this polygon P1
Is selected, the contents of the display buffer are updated with this polygon P2, and an image in which the polygon P2 is superimposed on the polygon P1 is formed (FIG. 2B). Further, the triangle-shaped polygon P3 located closest to the front is selected, the contents of the display buffer are updated by this polygon P3, and an image in which the polygons P1, P2, and P3 are sequentially overlapped is formed (FIG. 2C).

On the other hand, in a graphics drawing apparatus using the Z buffer method, a Z buffer is separately arranged in addition to the display buffer, and the Z coordinate value of each image data stored in the display buffer is held in this Z buffer. Further, in the graphics drawing apparatus using the Z buffer method, for the image data to be newly drawn, the contents of the display buffer and the Z buffer are updated only for the front side image data according to the comparison result with the Z coordinate value of the Z buffer. And display it.

That is, as shown in FIG. 3, in this graphics drawing apparatus, when displaying polygons P1, P2, and P3 whose Z coordinate values are values R, C, and T, the polygon located at the innermost position at the beginning is displayed. When processing P1, the polygon P1 is stored in the display buffer MG and the Z buffer MZ.
The image data and the Z coordinate value are stored respectively (see FIG. 3).
(A)).

When processing the polygon P2 located in front of the polygon P2, the graphics drawing apparatus uses the polygon P1 for the portion where the polygons P1 and P2 overlap each other according to the result of comparison with the Z coordinate value stored in the Z buffer MZ.
The content of the Z buffer MZ is updated with the Z coordinate value of 2 and the polygon P2 is also updated in this case for other parts of the polygon P2.
The Z coordinate value of 2 is stored in the Z buffer MZ (see FIG. 3).
(B)). Correspondingly, for the portion where the polygons P1 and P2 overlap, the contents of the display buffer MG are updated with the image data of the polygon P2,
For the other part of 2, the image data of the polygon P2 is stored in the display buffer MG.

In the case of further processing the foremost polygon P3, this graphics drawing apparatus similarly regards a portion where the polygons P2 and P3 overlap each other as a result of comparison with the Z coordinate value stored in the Z buffer MZ. The contents of the Z buffer MZ are updated with the Z coordinate value of P3, and in other parts of the polygon P3, the Z coordinate value of the polygon P3 is stored in the Z buffer MZ in this case (see FIG. 3).
(C)). Correspondingly, for the portion where the polygons P2 and P3 overlap, the contents of the display buffer MG are updated with the image data of the polygon P3, and the polygon P3 is updated.
The image data of the polygon P3 is stored in the display buffer MG with respect to the other portions of No. 3.

[0009]

By the way, in the hidden surface processing by the Z sort method, there is a problem that the load of sorting increases as the number of polygons increases, and the processing takes time. Further, as shown in FIG. 4, when the polygons P1 and P2 intersect each other, there is a problem that it becomes difficult to display the intersecting boundary without a sense of discomfort. Further, by updating the contents of the display buffer sequentially from the polygons located in the back, there is also a problem that image data not used for display is unnecessarily written in the display buffer.

On the other hand, in the hidden surface processing by the Z buffer method, the hidden surface processing can be reliably performed even in the case where polygons intersect by updating the contents of the display buffer in units of pixels. it can. That is, in the case of FIG. 4, the rhombus-shaped polygon P1 (FIG. 4A) in which the Z coordinate value of each pixel is the value 5 and the Z coordinate value of the image data that is obliquely inclined is from the value 8 to the value 2. This is a case where the parallelogram-shaped polygon P2 (FIG. 4B) intersects, and the Z buffer method can display the intersecting boundary without a sense of discomfort.

However, even in the hidden surface processing by the Z-buffer method, the image data not to be displayed is unnecessarily written in the display buffer depending on the selection order of polygons. That is, when processing the polygons arranged in the back and then processing the polygons in the front, as for the polygons arranged in the back, the display buffer and Z
The buffer is wastefully written. Further, there is a problem that the Z coordinate value stored in the memory is wastefully accessed.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a hidden surface treatment method capable of easily and surely performing hidden surface treatment.

[0013]

In order to solve such a problem, in the present invention, the Z coordinate values representing each object are compared and a plurality of objects in front of the viewpoint within a predetermined range are compared. After selecting more sequentially,
For these objects, the display image is formed by sequentially comparing the Z coordinate values of each pixel.

When the Z-coordinate values representing each object are compared and the object on the front side with respect to the viewpoint is sequentially selected from a plurality of objects within a predetermined range, when all objects are Z-sorted by that amount. In comparison, unnecessary objects can be easily removed from the processing target. Therefore, in the process of successively comparing the Z coordinate values of the respective pixels, unnecessary objects are omitted. As a result, the hidden surface can be easily processed.

Further, by sequentially comparing the Z coordinate values of the respective pixels to form a display image, it is possible to surely perform the hidden surface processing even when the polygons intersect each other. Further, by sequentially selecting from the object on the front side with respect to the viewpoint and comparing the Z coordinate values of the respective pixels, it is possible to sequentially process the pixels required for display, thereby omitting unnecessary writing processing to the video memory. You can also

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a graphics drawing device according to an embodiment of the present invention. Here, in this type of graphics drawing device 1, representative points are set in a matrix by a computer on the surface of a polygon which is a three-dimensional object, and the arithmetic processing applying the perspective transformation method is executed by each representative point. . Further, representative point data corresponding to the vertices of each triangular area is recorded in the main memory 2 so that each polygon is sequentially cut out into triangular areas by adjacent representative points. As a result, the graphics drawing apparatus 1 generates image data for each polygon by performing interpolation calculation processing between these representative points. In doing so, the main memory 2 is the main memory of this computer and records the coordinate data X, Y, Z, red, green, and blue luminance values R, G, B of each representative point for each triangular area. (Hereinafter, the data of the representative points of this triangular area are called the vertex data).

The Z sort processing circuit 3 searches the vertex data recorded in the main memory 2, selects the triangle area closest to the viewpoint, and calculates the initial value of the vertex data of this triangle area. Output to circuit 4. Then Z
The sort processing circuit 3 excludes this triangular area from the search target, searches for the vertex data of the remaining triangular area, and then sets the vertex data of the triangular area located in front of the viewpoint to the initial value calculation circuit 4. Output. In this way, the Z sort processing circuit 3 sequentially selects the vertex data from the triangular area located closest to the viewpoint and outputs the selected vertex data to the initial value calculation circuit 4, and the remaining number of each triangular area becomes When the search starts at 1/2, the search process ends.

As a result, the Z sort processing circuit 3 sets the triangular area recorded in the main memory 2 in the range of 1/2 of the triangular area from the front side with respect to the viewpoint.
The vertex data is sequentially selected, and, for example, a triangular area that does not actually need to be drawn and exists on the back side is excluded from the subsequent processing targets. In addition, a small triangular area that exists far from the viewpoint and that is hardly required to be displayed by the perspective transformation method is also excluded from the subsequent processing targets.

The initial value calculation circuit 4 calculates the initial value required for the interpolation calculation processing of the subsequent interpolation calculation processing circuit 5 from the vertex data of the triangular area thus output from the Z sort processing circuit 3. Here, the interpolation calculation processing circuit 5 is
By linear interpolation by A (Digital Differential Anarizer) calculation, Z coordinate values and brightness values R, G, B using the coordinate values X, Y in the triangular area as parameters are calculated. Therefore, the initial value calculation circuit 4 sequentially switches the Y coordinate values, calculates data for each change in the coordinate values X, Z, and the brightness values R, G, B at both ends of the triangular area, and uses these data as the initial values. Is output to the interpolation calculation processing circuit 5. The interpolation calculation processing circuit 5 sequentially switches the X coordinate values, performs linear interpolation processing by performing cyclic addition processing on the data of this initial value, and generates the above-mentioned triangular area data. As a result, the initial value calculation circuit 4 and the interpolation calculation processing circuit 5 convert the image data (R, G, B) of each triangular area and the data of the Z coordinate value into each X.
Generate and output for each Y coordinate value.

The memory interface 6 stores the brightness values R, G, B output from the interpolation calculation processing circuit 5 in the display buffer 7 and the corresponding Z coordinate values in the Z buffer 8. At this time, the memory interface 6 executes the hidden surface processing to which the Z buffer method is applied by stopping the storage processing in the display buffer 7 and the Z buffer 8 based on the Z coordinate value. That is, the memory interface 6 loads the corresponding Z coordinate value from the Z buffer 8 based on the XY coordinate value input from the interpolation calculation processing circuit 5, and inputs this Z coordinate value to the built-in Z value comparison circuit 10. To do.

The Z value comparison circuit 10 includes an interpolation calculation processing circuit 5.
By comparing the Z coordinate value input from the Z buffer with the Z coordinate value loaded from the Z buffer 8, the image data stored in the display buffer 7 and the image data output from the interpolation calculation processing circuit 5 are compared. , Which image data exists on the near side. Here, when the comparison result that the image data output from the interpolation calculation processing circuit 5 is present on the front side is obtained, the memory interface 6
Display image data R, G,
B is stored and the contents of the display buffer 7 are updated. In addition, the Z coordinate value of the corresponding image data is set to the Z buffer 8
To be stored. On the other hand, when the comparison result that the image data stored in the display buffer 7 is present on the front side is obtained, the storage in the display buffer 7 is stopped.

As a result, the memory interface 6 is
As described above with reference to FIG. 4, the diamond-shaped polygon P1 (FIG. 4A) in which the Z coordinate value is set to the value 5 and the parallelogram shape in which the diagonally tilted Z coordinate value is the value 8 to the value 1 Image data obtained by performing hidden surface processing on these polygons P1 and P2 with the Z coordinate value of 5 common to the two polygons P1 and P2 as a boundary when processing the polygon P2 (FIG. 4B). (FIG. 4C) is accumulated in the display buffer 7.

Further, the memory interface 6 transfers the image data of the display buffer 7 to the display controller 12 in a predetermined block unit in response to a request from the display controller 12.

The display controller 12 issues a display address to the memory interface 6 at a timing synchronized with the horizontal and vertical synchronizing signals of the monitor device connected to the graphics drawing device 1 to request the transfer of image data. Further display controller 1
2 holds the image data transferred from the memory interface 6 in the built-in buffer memory in response to this request, and outputs it to the output circuit 13 that follows in a predetermined cycle.

The output circuit 13 converts the image data into a digital value to be displayed on the monitor device, and then converts it into an analog signal for output. As a result, the graphics drawing device 1 displays various three-dimensional images on the monitor device.

With the above arrangement, in the graphics drawing apparatus, a representative point is set on the surface of a polygon which is a three-dimensional object, whereby a triangular area surrounded by adjacent representative points is set on each polygon. The coordinate values of these representative points are calculated in advance by a calculation process to which a perspective transformation method is applied by a computer, and the coordinate values X, Y, and Z of these representative points are calculated along with the brightness values R, G, and B of the respective representative points. It is stored in the main memory 2 for each triangular area.

In this way, the vertex data of the triangular area stored in the main memory in advance is searched for by the Z sort processing circuit 3 within a range in which the number of remaining triangular areas becomes 1/2 of the time when the search is started. Thus, the triangular areas located closest to the viewpoint are sequentially selected and output to the subsequent initial value calculation circuit 4. As a result, the vertex data of these triangular areas can be processed, for example, by a simple process that reduces the burden compared to the case of hidden surface processing by the Z-sort method. In addition, a small triangular area or the like that is distant from the viewpoint and hardly needs to be displayed by the perspective transformation method is excluded from the subsequent processing target, and the initial value calculation circuit continues in order from the viewpoint side with high possibility of display. 4 is output.

In practice, when the perspective transformation method is applied, the displayed area becomes smaller in the triangular area existing farther from the viewpoint and becomes larger in the triangular area on the front side. As a result, as in this embodiment, 1/2 of the time when the search is started
In the range up to, the triangular area on the near side is sequentially output, and the triangular area unnecessary for display can be excluded from the processing target in a practically sufficient range. It should be noted that the initial value calculation circuit 4 continues in this order from the viewpoint side having a high display possibility.
Output to the Z sort processing circuit 3 for processing time convenience.
Even if the processing in (3) is terminated midway, the object on the near side, which is easily noticeable, can be displayed, and the deterioration of the image quality of the displayed image can be effectively avoided by that amount, and the time management can be simplified.

In this way, the vertex data of the triangular area output to the initial value calculation circuit 4 is generated as initial value data, and in the subsequent interpolation calculation processing circuit 5, linear interpolation processing is performed using this initial value data. Then, the Z coordinate values, the red, green, and blue luminance values R, G, and B are generated for the pixels in each triangular area.

These data are compared with the Z value stored in the Z buffer 8 in the Z value comparison circuit 10 of the memory interface 6, whereby
It is determined which of the image data stored in the display buffer 7 exists on the front side, and the image data hidden in the image data stored in the display buffer 7 is excluded from the subsequent series of processing targets. On the contrary, when it is determined that the image data stored in the display buffer 7 exists before the image data, the contents of the Z buffer 8 are updated by the Z coordinate value, and the red, green, and blue luminance values R, Display buffer 7 for G and B
Stored in.

As a result, the Z sort processing circuit 3 performs the hidden surface processing by the Z buffer method on the triangular areas which are sequentially input from the front side while reducing the processing targets. At this time, the Z sort processing circuit 3 excludes a triangular area unnecessary for display from the processing target,
The access frequency to the display buffer 7 and the Z buffer 8 in the memory interface 6 is reduced by that amount, and unnecessary drawing is reduced. Further, since the vertex data of the triangular area is sequentially output from the front side with respect to the viewpoint, the display buffer 7 is displayed in the order of high display possibility.
Image data will be stored in. Therefore, with respect to the image data once stored in the display buffer 7, the frequency of rewriting can be reduced stepwise as compared with the case of the conventional Z buffer method, and the load required for processing can be reduced accordingly, and the Z coordinate value can be reduced. It is possible to allocate the time left for comparison. Further, regarding intersecting polygons, the boundaries can be displayed without a sense of discomfort.

The image data stored in the display buffer 7 in this way is displayed by the display controller 1.
2 is output to the output circuit 13 and the output circuit 13
Is displayed on the monitor device via.

According to the above configuration, the Z sort processing circuit 3
In, the remaining number of triangular areas is 1/2 of the beginning of the search
Up to, the vertex data of the triangular area is sequentially selected from the triangular area located closest to the viewpoint and output, and the hidden surface processing by the Z buffer method is executed in the memory interface 6. The triangular area unnecessary for display can be excluded from the processing target and the hidden surface processing can be performed by the Z buffer method, and the hidden surface processing can be performed simply and surely.

That is, in the Z sort processing circuit 3,
Even when the number of triangular areas increases by performing the search processing within a range in which the number of remaining triangular areas becomes ½ of that at the start of the search, compared with the case of the conventional Z sort method. The burden can be reduced. Further, regarding intersecting polygons, the boundaries can be displayed without a sense of discomfort.

Further, since the triangular area unnecessary for display is excluded from the processing target, the display buffer 7 and the Z buffer 8 in the memory interface 6 are correspondingly removed.
The frequency of access to is reduced, and unnecessary drawing is reduced. Further, since the vertex data of the triangular area is sequentially output from the front side with respect to the viewpoint, the image data once stored in the display buffer 7 has a rewriting frequency higher than that of the conventional Z buffer method. It is possible to reduce the number of steps, and the load required for the processing can be reduced accordingly, and the time remaining for comparison of Z coordinate values can be distributed.

In the above embodiment, the case where the Z sort processing circuit 3 executes the search processing within the range in which the number of remaining triangular areas becomes ½ of the search start time has been described. However, the present invention is not limited to this, and these ranges can be variously set within a practically sufficient range, and can be varied as necessary.

Further, in the above-described embodiment, the case where the three-dimensional object defined by the vertex data is simply subjected to the hidden surface processing and displayed is described, but the present invention is not limited to this, and in addition to this, for example, mapping is performed. It can be widely applied to processing.

Further, in the above-mentioned embodiment, the case where the graphics drawing device is constituted by the arithmetic processing circuit has been described, but the present invention is not limited to this, and a graphics image is created by arithmetic processing in a personal computer or the like. It can also be widely applied in cases.

[0040]

As described above, according to the present invention, the object on the front side with respect to the viewpoint is sequentially selected within a predetermined range with reference to the Z coordinate value representing each object.
By forming a display image with the Z coordinate value of each pixel as a reference, unnecessary drawing processing can be reduced and hidden surface processing can be performed by the Z buffer method. This enables simple and reliable hidden surface processing. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a graphics drawing device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a hidden surface process by a conventional Z sort method.

FIG. 3 is a schematic diagram for explaining a hidden surface processing by a conventional Z buffer method.

FIG. 4 is a schematic diagram for explaining the processing of a boundary in the hidden surface processing by the Z buffer method.

[Explanation of symbols]

1 ... Graphics drawing device, 2 ... Main memory,
3 ... Z sort processing circuit, 4 ... Initial value calculation circuit, 5 ...
... Interpolation calculation processing circuit, 6 ... Memory interface,
7 ... Display buffer, 8 ... Z buffer, 10 ...
… Z value comparison circuit, 12 …… Display controller

Claims (1)

[Claims] 1. A hidden surface processing method for a plurality of objects represented by three-dimensional coordinates, wherein Z coordinate values representing each of the objects are compared, and the object on the near side with respect to the viewpoint within the predetermined range is said. A hidden surface processing method, comprising: sequentially selecting from a plurality of objects, and then sequentially comparing Z coordinate values of respective pixels of the object to form a display image.