JP2000268191A - Hidden surface treatment method - Google Patents

Abstract

(57) [Summary] A hidden surface processing method capable of executing accurate hidden surface processing with a small processing amount in three-dimensional graphics processing is provided. A representative value of X, Y, Z coordinates representative of an object is obtained from coordinates of vertices of a plurality of polygons constituting an object (100), and a representative value of X, Y, Z coordinates of each obtained object is obtained. To determine the positional relationship between the objects and extract the Z-buffer application area (102). When the overlap of the representative values of the coordinates is detected in all three directions of X, Y and Z, the hidden surface processing (210) is performed by the Z buffer method, and when not detected, the hidden surface processing by overwriting (202) is performed. [Effect] The area using the Z buffer can be minimized,
The Z coordinate value comparison and update processing using the Z buffer can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hidden surface processing method for three-dimensional graphics processing, and more particularly to a hidden surface processing method that can be efficiently realized with a small processing amount.

[0002]

2. Description of the Related Art Conventionally, in three-dimensional graphics processing, a visible surface area and an invisible area of an object are determined.
Hidden surface processing for displaying only the visible surface region is performed. As a method of this hidden surface processing, a Z buffer method and a Z sort method are known. In this specification, a three-dimensional object is called an object, and a polygon forming the object is called a polygon.

The above-mentioned Z-buffer method can perform accurate hidden surface processing, but requires a memory for the Z-buffer (hereinafter simply referred to as a Z-buffer) and requires a long processing time for writing and reading to and from the Z-buffer. . On the other hand, the Z-sorting method does not require a Z-buffer, but has a disadvantage that the amount of processing for performing the sorting process is enormous, and hidden surface processing between objects having a complicated positional relationship cannot be performed correctly.

On the other hand, a method for easily performing accurate hidden surface processing by combining the Z buffer method and the Z sort method is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-305792. In this hidden surface processing method, Z-sorting is performed for all polygons in the screen in units of polygons, and then the Z-buffer method is applied to polygons within a predetermined amount in order from the polygon in front of the viewpoint. .

[0005]

However, according to the conventional example in which the above-described hidden surface processing is simply performed, in order to select a polygon to which the Z-buffer method is applied, Z-coordinate values of all polygons in the screen are compared. It is necessary to sort polygons. For this reason, when the number of polygons is large, the processing amount becomes enormous. Further, a memory for the Z buffer is required, and there is a problem that the memory amount is large.

An object of the present invention is to provide a hidden surface processing method capable of executing accurate hidden surface processing with a small processing amount.

Another object of the present invention is to provide a hidden surface processing method which can be realized with a Z buffer having a small memory amount.

It is another object of the present invention to provide a hidden surface processing apparatus using the above hidden surface processing method.

[0009]

In order to achieve the above object, a hidden surface processing method according to the present invention uses an X, Y, Z coordinate representative of an object from coordinates of vertices of a plurality of polygons constituting the object. Is determined, and the obtained X, Y, and Z coordinate representative values of each object are compared to determine the positional relationship between the objects.
Then, by determining the positional relationship, X, Y, Z
When the overlap of the representative values of the coordinates is detected in all three directions, the hidden surface processing is performed using the Z-buffer method, and when not detected, the hidden surface processing by overwriting is performed.

According to the above-described hidden surface processing method, it is possible to minimize an area where the hidden surface processing is performed by using the Z buffer method (hereinafter, referred to as a Z buffer application area). As a result, the processing of writing to the Z buffer, reading from the Z buffer, and comparing Z coordinate values can be reduced.

Therefore, the hidden surface processing apparatus according to the present invention using the above hidden surface processing method obtains representative values of X, Y and Z coordinates representing the object from the coordinates of the vertices of a plurality of polygons constituting the object. Means for determining the positional relationship between the objects by comparing the obtained representative values of the X, Y, and Z coordinates of each object, and X, Y, and Z by means for determining the positional relationship. Means for performing hidden surface processing using the Z-buffer method when overlap of coordinate representative values is detected in all three directions, and performing hidden surface processing by overwriting when not detected. It is a feature.

Further, the hidden surface processing method according to the present invention divides the Z-buffer application area into small areas, newly defines a polygon in which all vertices are included in each small area, and places the newly defined polygon in the small area. The hidden surface processing may be performed by using the above. With this hidden surface processing method, hidden surface processing can be performed for each small area even when the size of the Z buffer is smaller than the screen size.

The hidden surface processing apparatus is provided with means for dividing the Z-buffer application area into small areas and means for newly defining a polygon including all vertices in each small area. It is preferable to further comprise means for performing hidden surface processing by the Z-buffer method for each of the small areas using, and forming a display image in each of the small areas.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a hidden surface processing method according to the present invention will be described in detail using specific examples with reference to the accompanying drawings. In the following description, it is assumed that the polygon has a triangular shape. Further, the description will be made on the assumption that the horizontal direction of the display image plane is the X axis, the vertical direction is the Y axis, and the depth is the Z axis.

<Embodiment 1> This embodiment is a hidden surface processing method in which a rectangular parallelepiped containing each object is obtained, and processing is varied depending on the positional relationship between the obtained rectangular parallelepipeds. Specifically, rectangular parallelepipeds containing each object are X, Y,
When there are overlaps in all three directions in the Z direction, hidden surface processing using the Z buffer method is performed on polygons included in the overlap region. In other cases, the hidden surface processing is performed by drawing objects in order from objects farther from the viewpoint to objects closer to the viewpoint, and overwriting objects farther away with objects closer to the viewpoint. It is assumed that the object handled in this embodiment is a three-dimensional convex object.

FIG. 1 shows a processing flow of the hidden surface processing method of this embodiment. An outline of the hidden surface processing method will be described using this processing flow. Here, it is assumed that there are n objects in one screen.

First, in step 100, the inputted n object data is stored in the memory 10 as described later with reference to FIG. The object data input here describes data of polygons constituting each object, and corresponds to a polygon list (see FIG. 6C) described later.

Next, in step 101, a representative value of each object is obtained for each input object data. Here, the representative value refers to X,
These are the minimum and maximum values of the Y and Z coordinates, respectively.

Next, in step 102, using the obtained representative value, an area that requires processing by the Z-buffer method (Z-buffer application area) is extracted and described in a Z-buffer application area list.

Further, in step 103, an object sorting process is performed to create an object list in which the objects are arranged in order from the farthest from the viewpoint.

Next, the routine proceeds to a drawing processing routine 200, in which the object drawing processing is performed in the order described in the object list. That is, drawing processing is started in order from the object farthest from the viewpoint.

In step 201, it is first determined whether or not the first object to be drawn farthest from the viewpoint has a Z-buffer application area.

If the object has a Z-buffer application area, the flow advances to step 210 to perform hidden surface processing by the Z-buffer method. If the object does not have a Z-buffer application area, the flow advances to step 202 to perform hidden surface processing by overwriting. , Draw objects.

In step 203, it is determined whether or not there is an object to be subsequently subjected to a drawing process. Here, n
Since it is described that there are three objects, the process proceeds to step 204, the process proceeds to the next second farthest object drawing process, and the processes of steps 201 and 202 or steps 201 and 210 are performed in the same manner as described above.
Then, the process proceeds to step 204 via 3 to proceed to the next third farthest object drawing process. As described above, the drawing processing routine is repeated up to the n-th object. When it is determined in step 203 that there is no object to be processed, the drawing processing is terminated. The above is the outline of the hidden surface processing method of the present embodiment.

Incidentally, the hidden surface processing by the Z-buffer method in step 210 is expressed in detail as shown in FIG.
That is, if the object has a Z-buffer application area in step 201, it is determined in step 211 whether the pixel being processed in the object is outside the Z-buffer application area. If the pixel is not outside the Z-buffer application area, that is, if the pixel being processed is inside the Z-buffer application area, the process proceeds to step 212, where the Z buffer 12
Is performed, and only in the case of a visible pixel, writing to the frame memory 11 is performed, and the process proceeds to step 214. In the case of a visible pixel, the Z coordinate value of the Z buffer 12 is further updated to the Z coordinate value of the pixel being processed. On the other hand, if it is determined in step 211 that the area is outside the Z buffer application area, the flow advances to step 213 to overwrite the frame memory 11, and the flow advances to step 214. In step 214,
It is determined whether or not all the pixels in the object being processed have been processed, and if all the pixels have not been processed,
Returning to step 211, when the processing of all pixels is completed, the process proceeds to step 203 of FIG.

FIG. 2 is a block diagram of a hidden surface processing circuit for realizing the hidden surface processing method. The hidden surface processing circuit 15 includes a memory 10 for storing a polygon list, an object list, a Z buffer applicable area list, a frame memory 11 for storing display image data, and a Z buffer for storing Z coordinate values for one screen. 12 and so on. Further, the hidden surface processing unit 20 includes a representative value calculating unit 21, a Z buffer applied area extracting unit 22, an object sorting unit 23, a pixel interpolating unit 24,
Z buffer application area determination unit 25 and Z coordinate value comparison unit 2
Have 6. Further, the hidden surface processing unit 20 and each of the memories 10, 1
It has a data bus line 13 for exchanging data with the devices 1 and 12. The control unit 14 controls the operation of the hidden surface processing unit 20.

Hereinafter, description will be made with reference to the block diagram of FIG. First, data of an input object (polygon list) is stored in the memory 10. The contents of the object data include an object number, a polygon number constituting the object, vertex coordinates (X, Y, Z coordinates) of each polygon, and RGB color / luminance information at the vertices (FIG. 6 (c) polygon list). reference).

Next, the representative value calculation unit 21 reads the polygon list from the memory 10 via the data bus line 13 and obtains X, Y, and Z coordinates representing the object. In this embodiment, the minimum and maximum values of X, Y, and Z coordinates are obtained from the coordinates of all the vertices of all the polygons that make up the object, and these are used as representative values. Here, the minimum value and the maximum value of the X coordinate obtained as the representative value of the object are respectively xm
in, xmax, y coordinate minimum and maximum
The minimum and maximum values of min, ymax, and Z coordinate are set to zmin and zmax, respectively.

FIG. 3 shows the relationship between objects and their representative values in a three-dimensional space. X = YZ through xmin
A plane parallel to the plane, a plane parallel to the YZ plane passing through X = xmax, a plane parallel to the XZ plane passing through Y = ymin, Y
= Plane parallel to the XZ plane passing through ymax, Z = zmin
A plane parallel to the XY plane passing through XY passing through Z = zmax
A rectangular parallelepiped 30 having six planes parallel to the plane as planes
Is the smallest rectangular parallelepiped that includes the object 31 and whose faces are all parallel to one of the XY plane, the YZ plane, and the XZ plane. That is, xmin, xmax, ymin,
Determining ymax, zmin, zmax is equivalent to determining the position of the rectangular parallelepiped 30 containing the object 31. The position of a rectangular parallelepiped including the object is similarly obtained for all the objects existing on the screen. Note that these minimum and maximum values (xmin, xma
x, ymin, ymax, zmin, zmax) are hereinafter referred to as rectangular parallelepiped parameters.

Next, the Z-buffer application area extraction unit 22 determines the positional relationship between the rectangular parallelepipeds using the parameters of the rectangular parallelepiped, and creates a list to be used for the subsequent processing.
The positional relationship between two rectangular parallelepipeds is classified into two types: (1) a case where there is an overlap in a three-dimensional space, and (2) a case where there is no overlap in a three-dimensional space.

In the case of (1), since objects included in the rectangular parallelepiped may overlap in the three-dimensional space, the Z-buffer 12 is used to position the overlapping plane of the rectangular parallelepiped on the projection plane on the XY plane. Perform hidden surface processing by the method.

In the case of (2), after the object farther from the viewpoint is drawn on the frame memory 11, the hidden object processing is performed by drawing the object on the near side in the frame memory 11, that is, by overwriting. . Here, the drawing of the object is a valid polygon whose surface is facing the viewpoint from among the triangular polygons constituting the object (that is, the surface that can be seen from the viewpoint).
Means to draw. Polygons whose surfaces face down with respect to the viewpoint (that is, surfaces that cannot be seen from the viewpoint) are not drawn.

The positional relationship between the rectangular parallelepipeds is determined as follows. As an example, FIG. 4 shows a positional relationship between rectangular parallelepipeds each containing the object 1 and the object 2, and a procedure for checking the overlap will be described. FIG.
(A) shows the overlap on the XY plane, and (b) shows the overlap on the YZ plane.

First, the rectangular parallelepipeds including the object 1 and the object 2 are referred to as rectangular parallelepipeds 1 and 2, respectively. Further, xmin and xmax of the rectangular parallelepiped 1 are respectively represented by x
min1 and xmax1. Similarly, xmi of the rectangular parallelepiped 2
Let n and xmax be xmin2 and xmax2, respectively. At this time, the condition that the rectangular parallelepiped 1 and the rectangular parallelepiped 2 do not overlap in the X direction is xmax1 <xmin2 or xma
x2 <xmin1. Therefore, when this condition is satisfied, no overlap exists in the X direction. When this condition is not satisfied, it can be said that an overlap may exist in the X direction.

Similarly, in the Y direction and the Z direction, the presence or absence of the overlap is checked by using the parameters of the rectangular parallelepiped. X, Y, Z
When there is an overlap in all three directions, it can be classified into the above-mentioned (1) “when there is overlap in the three-dimensional space”. When there is no overlap in at least one of the three directions X, Y, and Z, And (2) “when there is no overlap in the three-dimensional space”.

As described above, as a result of classifying the positional relationship between the rectangular parallelepipeds, (1) “in the case of having an overlap in a three-dimensional space”
When the classification is made, the overlapping area on the XY plane is defined as a Z buffer application area Zb, and parameters defining the area are obtained. This parameter is called a region parameter. The area parameters are two X coordinates and two Y coordinates that define the four sides of the Z buffer application area Zb. In the example shown in FIG. 4, X = xmin2, xmax
1 and Y = ymin1, ymax2.

If there are three or more objects in the three-dimensional space, the positional relationship is classified according to the above procedure for all combinations of rectangular parallelepipeds containing each object, and the Z buffer application area Zb is obtained.

In the case of the above (1), hidden surface processing using the Z-buffer method is performed on the Z-buffer application area Zb in the rectangular parallelepiped area. Since the area other than the Z-buffer application area Zb is an area that does not require the Z-buffer method, polygons in a rectangular parallelepiped are drawn in order from the farthest from the viewpoint, and hidden surface processing by overwriting is performed.

The rectangular parallelepiped area classified in the above (2) is
Since the Z-buffer method is not required in the region (1) except for the region other than the Z-buffer application region, the hidden surface processing by overwriting is performed. For the hidden surface processing by this overwriting, the object sorting unit 23 performs a sorting process for arranging the rectangular parallelepipeds in the processing order, and arranges all the rectangular parallelepipeds in an order far from the viewpoint.

Next, a procedure for creating the object list and the Z-buffer application area list will be described. As an example, consider a case where four objects 1 to 4 exist in a three-dimensional space. FIG. 5 shows the positional relationship between the rectangular parallelepipeds 1 to 4 including the objects 1 to 4, respectively. In FIG. 5, (a) shows the overlap on the XY plane, and (b) shows the overlap on the YZ plane. Also, the object list in this case,
FIG. 6 shows the Z buffer application list. The processing for determining the positional relationship between the rectangular parallelepipeds is performed for the following six combinations of rectangular parallelepipeds. The six combinations are a combination of the cuboid 1 and the cuboids 2 to 4, a combination of the cuboid 2 and the cuboids 3 and 4, and a combination of the cuboid 3 and the cuboid 4.

As a result of the processing for determining the positional relationship by the Z-buffer application area extraction unit 22, the rectangular parallelepipeds 2 and 3 are classified into the above-mentioned (1) "in a case where they overlap in a three-dimensional space" and share the Z-buffer application area Zb. You can see that This Z-buffer application area Zb is defined as a Z-buffer application area 1, and an area number and an area parameter are described in the Z-buffer application area list (see FIG. 6B).

Further, the object sorting unit 23 calculates the zmin (Zin of the plane parallel to the viewpoint parallel to the XY plane) of each rectangular solid.
(Coordinates) to sort the rectangular parallelepipeds 1 to 4. As a result, the rectangular parallelepipeds are 3, 2, 4, and 1 in order of being farther from the viewpoint.
This result is described in the object list (FIG. 6A)
reference). In the object list, the presence or absence of the Z-buffer application area Zb and the number of the Z-buffer application area, if any, are described together with the object number (the number of the rectangular parallelepiped). The Z buffer application area list and the object list are written to the memory 10.

As described above, the object list, Z
After creating the buffer application area list, drawing processing is performed with reference to these lists. The outline of this processing will be described below.

First, the object list is read out one line at a time, and an object with the number described in each line is processed. For each object, read the polygon list that describes the polygon of that object,
Process the described polygons one by one. (Here, the polygon list is, as shown in FIG.
This is a list in which the coordinate values of the vertices, the color brightness, and the like are described for the polygons that make up each object, and are input from outside as object data. The pixel interpolator 24 performs a pixel interpolation process for each polygon to interpolate the color luminance of the pixels in the polygon from the coordinates and color luminance of the vertices of the polygon, and the frame memory 11
Write to. However, when processing an object having a Z-buffer application area Zb, that is, when there is a Z-buffer application area in step 201 in FIG.
It is checked whether or not the coordinates are included in the Z buffer application area Zb of the object (step 21 in FIG. 12).
1). That is, it is determined whether or not the pixel being processed is outside the Z-buffer application area, and if “no” (that is, if the pixel being included in the Z-buffer application area), it is determined in step 2
Proceeding to step S12, the pixel is processed using the Z buffer 12. However, the Z buffer 12 is defined as X,
This is a buffer memory that stores the Z coordinate value for the Y coordinate. If the pixel being processed is outside the Z-buffer application area, the flow advances to step 213 to write (overwrite) in the frame memory.

In the process using the Z buffer 12 in step 212, the Z coordinate
2, the Z coordinate value of the pixel being processed is compared with the Z coordinate value of the pixel being processed, and if the Z coordinate value of the pixel being processed is smaller, the pixel is visible; judge. If it is determined that the pixel is visible, the color luminance of the pixel is written to the frame memory 11 and the Z coordinate value of the Z buffer 12 is updated to the Z coordinate of the pixel. In addition,
In the initial state, the Z coordinate value of the Z buffer 12 is set to a Z coordinate sufficiently far from the viewpoint. Steps 211 and 212
Alternatively, the processing of steps 211 and 213 is performed on all the pixels in the object (steps 214 and 215),
When all the pixels are completed, the process proceeds to step 203 in FIG. 1. If there is the next object, the process proceeds to step 201. If there is no next object, the drawing process routine 200 ends.

Hereinafter, a case where the drawing process is performed using the object list of FIG. 6A will be described as a specific example.

First, the first line of the object list is read. In this case, since the object number is 3 and the Z-buffer application area Zb is 1, the description of the polygons constituting the object 3 is read from the polygon list shown in FIG. Perform pixel interpolation processing. At this time, if the X and Y coordinates of the processing pixel are within the Z buffer application area 1, the processing is performed using the Z buffer 12.

When the processing of the object 3 is completed,
In the frame memory 11, pixel data of the polygon of the object 3 is written. The Z buffer 12
Of the Z buffer application area 1 of the
The Z coordinate value of the polygon of the object 3 at the coordinate value is written.

Next, processing is performed on the object 2 described in the second line of the object list. The object 2 has a Z-buffer application area 1 like the object 3. Therefore, among the pixels in the polygon of the object 2, the pixels included in the Z buffer application area 1 are processed using the Z buffer 12. In the portion of the Z buffer 12 in the Z buffer application area 1 where the polygon pixels of the object 3 exist, the Z coordinate value of the object 3 has already been written. Therefore, the pixels of the polygons of the object 3 and the object 2 are XY
In the overlapping part on the plane, comparing the Z coordinate values with reference to the Z buffer 12 is equivalent to comparing the Z coordinate values of the object 2 and the object 3.

As a result of this comparison, when the pixel of the object 2 is closer to the viewpoint, the pixel of the object 2 is written into the frame memory 11 and the Z coordinate value of the Z buffer 12 is rewritten to the Z coordinate value of the object 2. If the pixel is not included in the Z buffer application area 1, the Z buffer 12
Is written to the frame memory 11 without referring to. When the processing of the object 2 is completed, the pixels of the object 2 and the object 3 have been written in the frame memory 11 in a state where the hidden surface processing has been performed.

Subsequently, according to the object list, the processing of the object 4 and the object 1 is performed in order. Since neither the object 4 nor the object 1 has the Z-buffer application area Zb, the pixels of the polygons constituting each object are written into the frame memory 11 without referring to the Z-buffer 12.

As described above, as a result of performing the processing in the order of the objects 3, 2, 4, and 1 in accordance with the object list, data obtained by performing the hidden surface processing of the objects 1 to 4 is written in the frame memory 11. . By reading and displaying the frame memory 11, a desired display image can be obtained.

As described above, in this embodiment, a three-dimensional object is represented by a rectangular parallelepiped including the object.
The order of the hidden surface processing is determined by examining the positional relationship between the rectangular parallelepipeds. For this reason, the processing amount of the sort processing is smaller than in the case of performing the sort processing in units of polygons as in the conventional example. In addition, since the area to which the Z-buffer method is applied can be minimized, the amount of processing for writing to and reading from the Z-buffer memory can be reduced. That is, the area using the Z buffer can be minimized, and the Z coordinate value comparison and update processing using the Z buffer can be reduced.

<Embodiment 2> FIG. 7 is a block diagram showing another configuration example of a hidden surface processing circuit for realizing the hidden surface processing method of the present invention. This embodiment is a hidden surface processing method in which one Z buffer is shared by a plurality of areas when the size of the Z buffer is smaller than the size of the screen. 7, the same components as those of the embodiment shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, the configuration of the present embodiment is different from the configuration in that the Z-buffer application area division unit 71 and the polygon division unit 72 are added to the hidden surface processing unit 20 of the hidden surface processing circuit 15 shown in FIG. This embodiment is different from the above embodiment in the size. The size of the Z buffer 73 in the hidden surface processing circuit 70 shown in FIG. 7 is m pixels × n pixels. Here, the screen size is M pixels × N pixels, and m, M, and n
And N are assumed to be m <M and n <N. That is, unlike the above embodiment, the Z buffer 73 of the present embodiment
Is a Z buffer having a memory amount for storing Z coordinate values smaller than one screen.

Hereinafter, the hidden surface processing method of this embodiment will be described. As in the above embodiment, the representative value calculation unit 21 obtains a rectangular parallelepiped containing the object based on the object data input to the memory 10. And Z
The buffer application area extraction unit 22 determines the positional relationship between the rectangular parallelepipeds, and the object sort unit 23 creates an object list in which the objects are arranged in order from the farthest from the viewpoint. Further, when the positional relationship between the rectangular parallelepipeds is determined and the classification is determined to have the overlap in the three-dimensional space, the Z-buffer application area extraction unit 22 obtains the area parameter of the Z-buffer application area Zb.

Further, the Z-buffer application area dividing section 71 divides the Z-buffer application area Zb so as to be included in the size of the Z-buffer 73. Here, an example of division of the Z buffer application area is shown in FIG. As shown in FIG.
For example, from the upper left to the upper right, the lower left,
The size of the Z buffer 73 is applied in the lower right order, and the Z buffer application area Zb is divided into Z buffer sub-areas S1 to S4. Note that the order of division is not limited to this order.

Next, in the polygon division section 72, for each of the Z buffer sub-areas S1 to S4,
Buffer sub-region Sk (k = positive integer, in this example k =
Extract polygon data included in (1) to (4). Here, FIG. 9 shows an example of the relationship between the Z buffer sub-region Sk and the polygon to be extracted.

FIG. 9 shows an example in which the Z buffer sub area Sk includes a part of the polygon P1. At this time, the quadrangular portion included in the Z buffer sub-region Sk is divided into two polygons, a polygon P1-1 and a polygon P1-2. Polygon P1-1 and polygon P1-
2 is a polygon in which all vertices are included in the Z buffer sub-region Sk. The parameters of the Z buffer sub-region are:
A Z buffer application area number as shown in FIG.
It is described in a Z buffer sub area list composed of the number of Z buffer sub areas, sub area numbers, and coordinate values. The vertex data and the color / luminance data of the polygon newly defined in the Z buffer sub area are composed of the Z buffer sub area number, the number of sub polygons, the sub polygon number, and the vertex coordinates as shown in FIG. Described in the sub polygon list. The sub-polygon list is collectively described for a plurality of objects sharing one Z-buffer sub-area. That is, the information of the polygon data in the Z buffer sub-area is collectively described in the sub-polygon list. These Z-buffer sub-area lists,
The sub-polygon list is stored in the memory 10.

After the above list is created, a drawing process is performed as follows. Here, FIG. 11 shows an outline of a drawing processing flow in the hidden surface processing method of the present embodiment. The difference from the drawing processing flow shown in FIG. 2 of the embodiment is that in the drawing processing routine 200, the hidden surface processing part 210 by the Z buffer method in FIG. A part 220 and a step 230 for determining whether or not the Z-buffer application area has not been processed;
The point is that the processing part 240 is replaced with a processing part 240 in the Z buffer application area which is composed of steps 241 to 243.

In the drawing process of the present embodiment, the drawing process is started in order from the object farthest from the viewpoint in accordance with the object list, and the process is performed for each object in the same manner as in the above embodiment.

In step 201, the Z-buffer application area determination unit 25 determines whether or not the object to be drawn has a Z-buffer application area.
In step 1, it is checked whether or not the pixel being processed is outside the Z-buffer application area, that is, whether or not the pixel being processed is included in the Z-buffer application area. If the pixel being processed is outside the Z-buffer application area (if not included in the Z-buffer application area), the process proceeds to step 222,
If it is included in the Z-buffer application area, the process proceeds to step 224, and the processing from step 221 is repeated for the next pixel. That is, only when the pixel under processing is not included in the Z-buffer application area, the pixel is stored in the frame memory 11.
And perform hidden surface processing by overwriting.

Next, the process proceeds to step 223, where it is determined whether or not the hidden surface processing has been completed for all pixels outside the Z-buffer application area in the object. If not, the process returns to step 221 for the next pixel, and the same. Repeat the process. If processing of all pixels outside the Z buffer application area is completed, step 2
Proceed to 30.

In step 230, it is determined whether or not the object being processed has an unprocessed portion of the Z-buffer application area. If there is an unprocessed part, the process proceeds to the processing section 240 in the Z-buffer application area. Proceed to step 203.

In step 203, it is determined whether or not there is an object to be rendered. If so, the same processing from step 201 is repeated for the next object via step 204.

The processing of the pixels in the processing portion 240 in the Z-buffer application area is performed in the following procedure independently of the pixel processing of the polygon outside the Z-buffer application area. If there is a Z-buffer application area, the Z-buffer application area dividing unit 71 divides the Z-buffer application area into Z-buffer sub-areas so as to be included in the size of the Z-buffer 73 as described above. The parameters of the Z buffer sub area are described in the Z buffer sub area list. Then, polygon data included in each Z buffer sub-region is extracted by the polygon division unit 72 and described in the sub-polygon list. These lists are stored in the memory 10.

The drawing process is performed for each Z buffer sub-region (hereinafter simply referred to as a sub-region) in the Z-buffer application region.

In step 241, hidden surface processing is performed on one of the sub-regions by the Z-buffer method. Here, first,
With reference to the Z-buffer sub-area list, a sub-area number and an area parameter are obtained. Next, polygon data included in the sub-region is obtained with reference to the sub-polygon list, and processing is performed for each polygon. For each polygon, the pixel interpolating unit 24 interpolates the pixels in the polygon, performs hidden surface processing using the Z buffer 73, that is, performs hidden surface processing using the Z buffer method, and writes the result in the frame memory 11. After processing all polygons in that sub-region,
Proceeding to the next step 242, it is determined whether there is a next sub-region to be processed. If there is a next sub-region, the process proceeds to step 243, the Z buffer 73 is initialized, and the process returns to step 241 to perform the same processing for the next sub-region.

If it is determined in step 242 that the processing has been completed for all the sub-areas within the Z-buffer application area, the drawing processing of the Z-buffer application area for the object being processed is ended. Therefore, the process proceeds to step 203 to determine the presence or absence of the next object to be subjected to the drawing process. If there is, the process proceeds to step 204, and returns to step 201 to perform the same process on the next object. On the other hand, if it is determined that there is no next object, the drawing process is terminated.

In the flowchart of FIG. 11, the case where the Z buffer applicable area is present at step 201 and the processing 240 inside the Z buffer applied area is performed after the processing 220 outside the Z buffer applied area, but the order is reversed. But it doesn't matter.

In this embodiment, the objects are processed in the order described in the object list. However, regarding the Z-buffer application area, among the two objects sharing the Z-buffer application area, the object list is used first. Before or after processing the object described in. For example, in the example of four objects used in the description of the first embodiment (see FIG. 5), objects 3, 2, 4, and 1 are described in the object list in this order. The objects 3 and 2 share the Z-buffer application area 1 as shown in FIG. In this case, the order of the processing is a part of the object 3 other than the Z buffer application area,
The Z-buffer application area 1, the part of the object 2 other than the Z-buffer application area, the object 4, and the object 1 in that order.

As described above, in the present embodiment, when an object to be processed has a Z-buffer application area, pixel processing differs between the object outside the Z-buffer application area and inside the Z-buffer application area. That is, pixels outside the Z-buffer application area overwrite the frame memory, but pixels in the Z-buffer application area are processed in units of the Z-buffer sub-area.

Further, the Z buffer application area of each object needs to be processed only once. For example, when a certain Z buffer application area is commonly referred to by the object 1 and the object 2, when the object 1 is processed, the Z
If the processing of the buffer application area is performed, the Z buffer application area does not need to be processed when the object 2 is processed. Therefore, in the processing of each object, only when the Z buffer application area is unprocessed, the Z buffer sub area unit is used. May be performed. In order to determine whether the Z-buffer application area is unprocessed or processed, for example, a 1-bit item indicating the processing state of the Z-buffer application area is added to the item of the Z-buffer application area list shown in FIG. It is possible to add a flag, process each Z-buffer application area once, and then set the flag.

In this embodiment, since the hidden surface processing can be realized with a small Z buffer amount without having the memory amount of the Z buffer for one screen, in addition to the effect of the above embodiment, the memory amount of the hidden surface processing circuit is further increased. This has the effect of reducing noise.

The hidden surface processing method of the present invention described in the first and second embodiments and the hidden surface processing apparatus to which the hidden surface processing method is applied include a memory for storing data of a three-dimensional object and the like, Z buffer for storing coordinate values, C
A three-dimensional graphics rendering device having a frame memory for storing display data to be displayed on a display device such as an RT, and an arithmetic processing circuit for performing arithmetic processing on image data such as object data, and arithmetic processing in a personal computer or the like 2 and FIG. 7 are provided in a part constituting an image data arithmetic processing function by hardware and / or software.
This can be realized by providing the arithmetic processing function described in the hidden surface processing unit 20 in the block diagram of FIG.

The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the spirit of the present invention. It is.

For example, in the above-described two embodiments, the parameters of the rectangular parallelepiped containing the object are obtained as the representative values of the object. The parameter of the minimum rectangular parallelepiped including all the valid polygons may be obtained. In this case, the processing amount for obtaining the parameters of the rectangular parallelepiped can be further reduced.

In the above description, an object having a three-dimensional convex shape is assumed as the object. When a concave object is handled, the object can be similarly processed by decomposing the object into a plurality of convex objects. In this case, among a plurality of cuboids including a plurality of objects generated by decomposition, adjacent cuboids have an overlap in a three-dimensional space.
However, it is clear that objects included in adjacent rectangular parallelepipeds do not intersect. That is, in this case, a Z-buffer is not required, and hidden surface processing by overwriting can be performed. Therefore, a convex object generated by decomposing a concave object is treated separately from other cases by adding the decomposition information, that is, by treating it as an exclusion area of the Z buffer application area, It is possible to reduce the processing amount.

[0078]

As is clear from the above-described embodiment, according to the hidden surface processing method of the present invention, a three-dimensional object is
Since the process is determined by examining the positional relationship between the objects by representing the object as a rectangular parallelepiped, the processing amount of the sort process is smaller than when the sort process is performed in units of polygons.

Further, by minimizing the area where the Z buffer is used, the processing of comparing and updating the Z coordinate value using the Z buffer can be reduced. As a result, it is possible to provide a hidden surface processing method and apparatus capable of executing accurate hidden surface processing with a small processing amount.

Further, even when the Z buffer amount is small,
Since the Z buffer can be shared by a plurality of areas, a hidden surface processing device with a small amount of memory can be realized.

[Brief description of the drawings]

FIG. 1 is a processing flowchart showing a first embodiment of a hidden surface processing method according to the present invention.

FIG. 2 is a block diagram of a hidden surface processing circuit for realizing the hidden surface processing method according to the first embodiment;

FIG. 3 is a diagram showing a relationship between objects in a three-dimensional space and their representative values in the hidden surface processing method according to the present invention.

4A and 4B are diagrams illustrating a Z-buffer application area in two rectangular parallelepipeds including an object, wherein FIG. 4A illustrates an example of an overlap on an XY plane, and FIG. 4B illustrates an example of an overlap on a YZ plane. It is.

5A and 5B are diagrams illustrating a Z-buffer application area in four rectangular parallelepipeds including an object, wherein FIG. 5A illustrates an example of an overlap in an XY plane, and FIG. 5B illustrates an example of an overlap in a YZ plane. It is.

FIG. 6 is a diagram showing an example of a list used in the hidden surface processing method according to the present invention.
FIG. 3B shows a Z buffer application area list, and FIG. 3C shows a polygon list.

FIG. 7 is a block diagram of a hidden surface processing circuit for realizing the hidden surface processing method of the second embodiment.

FIG. 8 is a diagram illustrating an example of division of a Z-buffer application area in the second embodiment.

FIG. 9 is a diagram illustrating an example of polygon division in the second embodiment.

FIGS. 10A and 10B show an example of a sublist used in the second embodiment. FIG. 10A shows a Z buffer sub area list, and FIG. 10B shows a sub polygon list.

FIG. 11 is a flowchart of hidden surface processing according to the second embodiment.

FIG. 12 is a flowchart showing step 210 of FIG. 1 in detail.

[Explanation of symbols]

10 memory, 11 frame memory, 12 Z buffer, 13 data bus line, 14 control unit, 15 hidden surface processing circuit, 20 hidden surface processing unit, 21 representative value calculation unit,
22: Z-buffer application area extraction unit, 23: object sort unit, 24: pixel interpolation unit, 25: Z-buffer application area determination unit, 26: Z coordinate value comparison unit, 30: rectangular parallelepiped containing object, 31: object, 70: Hidden surface processing circuit, 71: Z-buffer application area division unit, 72: Polygon division unit, 73: Z buffer.

Continued on the front page (72) Inventor Takashi Nakamoto 5-2-1, Kamizuhoncho, Kodaira-shi, Tokyo F-term (reference) in System LSI Development Center, Hitachi, Ltd. 5B080 AA13 GA02

Claims (6)

[Claims] 1. A method of processing a hidden surface of a plurality of objects represented by three-dimensional coordinates of X, Y, and Z, wherein three-dimensional regions representative of the plurality of objects are respectively obtained, and the plurality of three-dimensional regions are connected to each other. A three-dimensional overlap, a Z-coordinate value of pixels of the plurality of objects included in the overlap is compared to form a display image. 2. The three-dimensional area includes, among a plurality of polygons constituting an object, valid polygons whose faces are directed to the viewpoint and all six faces are XY planes and Y faces.
2. The hidden surface processing method according to claim 1, wherein the surface is a minimum rectangular parallelepiped parallel to any one of the Z plane and the XZ plane. 3. The minimum rectangular parallelepiped is X,
3. The hidden surface processing method according to claim 2, wherein the surface is a rectangular parallelepiped represented by a maximum value and a minimum value at each of the Y and Z coordinates. 4. A three-dimensional overlapping portion between the plurality of three-dimensional regions is divided into a plurality of small regions, and Z
The hidden surface processing method according to claim 1, wherein the coordinate values are compared. 5. A new polygon whose vertices are included in each small area is newly defined based on the data of the polygons included in the plurality of small areas. The hidden surface processing method according to claim 4, wherein an image is formed. 6. A memory for storing data of a three-dimensional object, a Z buffer for storing Z coordinate values of the object,
A hidden surface processing device having a frame memory for storing display data to be displayed on a display device, and a processing circuit for performing hidden surface processing of the data of the object, and a control unit for controlling the processing circuit; By comparing the representative values of the X, Y, and Z coordinates representing the object from the coordinates of the vertices of the plurality of constituent polygons with the representative values of the X, Y, and Z coordinates of each obtained object, X, by means for determining the positional relationship between the objects, and means for determining the positional relationship
Means for performing hidden surface processing using the Z-buffer method when overlap of representative values of coordinates is detected in all three directions of the Y and Z directions, and performing hidden surface processing by overwriting when no overlap is detected. A hidden surface processing device provided at least in a circuit.