JPH0750514B2 - 3D graphic display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a three-dimensional graphic display, and particularly a three-dimensional graphic capable of displaying a three-dimensional shape on a display device so as to be easily grasped. Regarding display device.

[Prior Art] In displaying a three-dimensional figure, an object is approximated by a polyhedron,
The polygons that compose this are displayed while performing hidden surface removal and smooth shading one by one. For more information on this method, see “Fundamentals.” James D. Foley and Andrees Van Damme.
Of Interactive Computer Graphics "Addison Wesley Publishing Company, 1982 (James D. Foley, Andries Van Dam," Fundam
entals of Interactive Computer Graphics ", Addison W
esley Publishing Company, 1982), Chapters 15: 1 and 16: 4. Further, examples of this type of device include US Pat. No. 4,475,104.

On the other hand, in order to display the three-dimensional shape of the three-dimensional figure in an easy-to-understand manner, the edges of the polygons forming the approximate polyhedron are painted in a color different from that of the inside. This display method is based on the computer graphics standard PHIGS (Pro
grammers Hierarchical Interactive Graphics Syste
In m), there are also regulations regarding the display of the edges of the fill area. For more information about this,
See Information Processing Society of Japan, Graphic Interface and Standardization Workshop Material PHIGS, September 17, 1985, page 20.

Conventionally, as shown in US Pat. No. 4,475,104, when displaying a polygon, the polygon is decomposed into triangles and then displayed. Although it is necessary to display the edge and the edge generated by dividing the edge into triangles separately, this point has not been taken into consideration in the past, and after displaying the polygon, the edge was displayed again.

On the other hand, in the display of two-dimensional figures, Japanese Patent Application No. 57-181311
As described in No. 3, the edge is stored in a special memory as pixel information, and at the time of painting processing, this memory is referred to for each pixel to determine whether this pixel is an edge. By not displaying the pixels and displaying the edges separately,
Preventing double writing of borders is done.
This conventional example is for displaying a two-dimensional figure with a border, and is not for solving the problem of hidden surface removal in the three-dimensional figure display described later.

[Problems to be Solved by the Invention] When the above-mentioned conventional technique, that is, when the polygon is filled and then the edge is drawn, the following problems occur.

That is, the depth coordinate value (that is, the Z coordinate) is calculated at the time of painting processing and edge drawing for hidden surface removal. The Z coordinate of the edge portion calculated at the time of painting processing and the Z coordinate calculated at the time of edge drawing are The calculation methods are different, so they do not match. If the pixel whose Z coordinate calculated at the time of painting is a value in front of the one calculated at the edge, even if the edge is drawn afterwards, the pixel will remain filled due to the hidden surface removal processing. , The edges are not displayed properly.

This point will be explained in a little more detail. Z when painting
The coordinates are calculated as follows. As discussed in Nikkei Electronics, No. 392 (1986), pages 189 to 190, when painting a figure divided into triangles or trapezoids, the Z coordinate of each pixel of these edges, that is, the side, is the edge. Interpolation is performed from the values at both ends according to the Y coordinate value. That is, the increment of the Z coordinate with respect to the increase of the Y coordinate is obtained, and the increment is added every time the Y coordinate is updated by +1.

On the other hand, the calculation of the Z coordinate in drawing the edge is as follows. First, the edge is drawn by generating a line segment. As discussed in Foley et al., Chapter 11, Section 2, line segment generation is usually handled by the incremental algorithm or its improved Bresenham algorithm.
In these algorithms, when the absolute value of the slope of the line segment is smaller than 1, that is, when the change amount in the X direction between both ends of the line segment is larger than the change amount in the Y direction, the X coordinate is increased by 1. The Y increment of is added every time the X coordinate is updated. In the opposite case, when the change amount in the Y direction is larger than the change amount in the X direction, the X increment is added every time the Y coordinate is updated. This two-dimensional line segment generation can be extended to a three-dimensional line segment generation by adding a process of adding Z increment in addition to adding X increment or Y increment.

As described above, the Z coordinate of the pixel on the edge, that is, the side in the painting process is always calculated by the interpolation along the Y direction, whereas the change in the drawing of the edge, that is, the generation of the line segment is large. Interpolation is performed along the axis. Therefore, when the amount of change in the X direction is large, interpolation is performed along the X axis, and the Z coordinate of the edge portion differs between the case of painting and the case of drawing an edge. As a result, when the edge and the inside thereof are drawn in different colors, if the edge in the filling process is determined to be in front of the edge drawn in the straight line, only that portion of the edge becomes different in color.

The same problem also occurs when drawing a line or a figure having a color different from the color of the polygonal figure to be painted on the plane.

An object of the present invention is to provide a three-dimensional graphic display device capable of clearly displaying the first and second three-dimensional graphics that have been subjected to hidden surface elimination processing on the display device in order to solve the above problems. It is in.

[Means for Solving Problems] In order to achieve the above object, the present invention provides a graphic information memory, a frame memory, and a depth value memory that stores the depth coordinates of a display graphic at the frontmost position in each pixel. , A depth value memory that stores the depth coordinates of the display graphic that is closest to each pixel, and the hidden surface removal processing is performed based on the depth coordinates of the display graphic that is closest to each pixel stored in the depth value memory. The first three-dimensional figure subjected to the hidden surface removal processing is drawn, the display information of the color or the brightness in each pixel is stored in the frame memory, and the area in which the first three-dimensional figure is drawn is shown. Information is stored in the graphic information memory in association with each pixel, and based on the information indicating the drawn region of the first three-dimensional graphic stored in the graphic information memory, the first three-dimensional graphic is displayed. Second A drawing processor that controls drawing of the three-dimensional figure to store display information of color or brightness in each pixel for the second three-dimensional figure in the frame memory, and each pixel stored in the frame memory by the drawing processor And a display device for displaying the first and second three-dimensional graphics that have been subjected to the hidden surface removal processing by reading out the display information of the color or the luminance in the above-mentioned three-dimensional graphic display device.

The "different color" includes the case where only the brightness is different. The “painting process” may be a shading process. The "other surface" includes lines and points.

[Operation] FIG. 1A shows a conceptual diagram for explaining the concept of the present invention. Consider a case where a three-dimensional figure that has undergone hidden surface removal and shading processing is displayed on the display screen.

First, after clearing the graphic information memory, graphic information such as edges is written in the graphic information memory. That is, the presence / absence information of dots such as edges is written corresponding to the X and Y coordinates. At this time, preferably, the Z coordinate of the dot on the frontmost surface of each pixel is written in the depth value memory, and the color information of the dot is written in the frame memory. The writing of edges and the like to the graphic information memory must always be performed before the painting processing, but the drawing of edges and the like to the frame memory may be performed after the painting processing.

At the time of painting processing of one polygon, when the pixel to be written is recognized by referring to the graphic information memory and corresponding to the pixel stored in the graphic information memory, the pixel is assigned the Z coordinate. Regardless of, it is determined that it is hidden by another surface. As a result, pixel writing for filling the frame memory is not performed for that pixel. In this manner, there are no pixels in which the drawing of the edge and the filling process are performed in duplicate, and it is possible to prevent the edge and the like from not being drawn normally due to the difference in the calculation method of the Z coordinate.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1B to 5. FIG. 1B shows the overall configuration of a device to which the present invention is applied. Reference numeral 1 is a graphic data buffer, which stores the coordinates and brightness of the vertices of the polygons forming the approximate polyhedron to be displayed in the three-dimensional space. Reference numeral 2 denotes a drawing processor, which is composed of a microprocessor and takes in polygon information on the graphic data buffer to perform display processing. Reference numeral 3 denotes a frame memory, which stores image information including luminance or color information corresponding to each pixel (X, Y coordinates), and is composed of a plurality of planes so that color shading can be displayed. In advance, the information of the designated color is written (drawn) at the pixel (X, Y coordinate) position which becomes the edge of the polygon. Depth value memory 4 stores the depth value of each pixel, that is, the Z coordinate, in order to perform hidden surface removal by the depth buffer method. Reference numeral 5 is an edge memory (graphic information memory), and 1 is written in a portion corresponding to a pixel serving as an edge of a polygon. The edge memory consists of one plane. A display device 6 displays an image output from the frame memory 3.

FIG. 2 shows a flow chart 7 when the drawing processor 2 displays a polygon with a border. Polygon 8 displayed in Fig. 3
Indicates. As will be described later, the polygon 8 is divided into three trapezoids or triangles in which the upper base or the lower base of the trapezoid is a point, and the display processing is performed. That is, the polygon 8 is divided into a triangle 81, a trapezoid 82 and a triangle 83 for processing.

The edge memory 5 is cleared to zero in block 71 of the flowchart 7. In block 72, the hidden surface is erased based on the depth value (Z coordinate) stored in the depth memory as shown in FIG. 2, and the line segment (graphic area) of the edge is converted into the pixel position (X, Y coordinate). ), The designated edge color is written in the frame memory 3, and at the same time, the edge line segment (graphic area) is shown in the edge memory 5 and “1” for inhibiting writing to the frame memory 3 is displayed. "Write. As a result, as shown in FIG. 4, 1 is written in the portion indicated by the circle in the edge memory 5.
For details of line segment generation, see Chapter 11 Section 2 of the above-mentioned book by Fori et al. The square given in block 73 is divided into trapezoids. The trapezoidal division procedure is not directly related to the present invention, and therefore its description is omitted. At block 74, the trapezoid is filled. In judgment 75, it is judged whether or not all the trapezoids have been painted. If not completed, then the next trapezoid is painted.

The trapezoidal filling process is based on Nikkei Electronics No.392 (19
86) Fill along scan line 811 shown in FIG. 3 as discussed on pages 189-190. The entire trapezoid is filled by processing from the bottom scan line to the top scan line of the trapezoid. FIG. 5 shows a flowchart 9 of the scan line drawing process. In the block 91, the scan lines, here, the X coordinates of the end points 8111 and 8112 of the scan line 811, Z
The coordinates and the brightness I are obtained from the values of the vertices V ₁ , V ₂ , V ₃ and V ₄ of the polygon. That is, the value of the end point 8111 is equal to the vertex V ₂ and the vertex
From V ₁ , the value of the end point 8112 is obtained by interpolation from the values of the vertices v ₂ and V ₃ . At block 92, X along the scan line
The increment of the Z coordinate and the increment of the brightness I when the coordinate increases are obtained from the values at both ends of the scan line. In block 93, the values of the X coordinate, Z coordinate, and brightness I of the current pixel to be painted (drawn) are set to the value of the left end 8111. In the judgment 94, the current pixel, that is, the edge memory at the position of the left end 8111 is read and it is judged whether "1" has been written, and 1
If is set, writing to the frame memory 3 is suppressed,
Jump to determination 97 of end of all pixels. Otherwise,
Proceeding to judgment 95, here, the depth value at the position of the current pixel to be painted (drawn) is read from the depth value memory 4 and it is judged whether or not it is hidden on the other surface. If it is hidden, jump to decision 97. If it is not hidden, the brightness I of the current pixel is written in the position of the current pixel in the frame memory 3 in the next block 96. The Z coordinate of the current pixel is also written in the depth value memory 4. In the judgment 97, it is judged whether or not the processing of all the pixels on the scan line has been completed. . Ie X
The coordinate is incremented by 1, the Z coordinate and the brightness I are added by the respective increment values obtained in the block 92, the process jumps to the decision 94, and the above process is repeated.

Although only the edges of the polygon have been described in the above embodiments, the present invention can be applied to any figure such as a line on the surface or a surface other than the edge when the polygon is filled.

EFFECTS OF THE INVENTION According to the present invention, it is possible to prevent the drawing of a three-dimensional figure such as an edge and the painting processing (drawing processing) on the same surface from being duplicated in the same pixel. There is an effect that it is possible to display clear first and second three-dimensional figures without causing pixel omission or the like in the figure display such as edges accompanying the hidden surface processing of the figure.

[Brief description of drawings]

FIG. 1A is a conceptual diagram of the present invention, FIG. 1B is a block diagram of the overall configuration of an apparatus to which the method of the present invention is applied, FIG. 2 is a flowchart showing a three-dimensional bordered painting processing procedure, and FIG. FIG. 4 is an explanatory diagram showing a polygon for performing three-dimensional filling with a border, FIG. 4 is an explanatory diagram showing a method of storing a border in a graphic information memory (edge memory), and FIG. 5 is a process for painting one scan line. It is a flowchart which shows a procedure. 1 ... Graphic data buffer 2 ... Drawing processor 3 ... Frame memory 4 ... Depth value memory 5 ... Graphic information memory (edge memory) 6 ... Display device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takehiko Nishida Inventor Takehiko Nishida 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Inside the Omika factory of Hitachi, Ltd. (56) Reference JP-A-63-59684 (JP, A) JP 62-49571 (JP, A)

Claims (1)

[Claims] 1. A graphic information memory, a frame memory, a depth value memory for storing depth coordinates of a display graphic in the foremost position in each pixel, and a display in the foremost position in each pixel stored in the depth value memory. Perform hidden surface removal processing based on the depth coordinates of the figure,
Information for indicating the area in which the first three-dimensional figure is drawn while storing the display information of the color or brightness of each pixel in the frame memory by drawing the first three-dimensional figure subjected to the hidden surface removal processing. Is stored in the graphic information memory in association with each pixel, and based on the information indicating the drawn area of the first three-dimensional graphic stored in the graphic information memory, Control the drawing of the second three-dimensional figure,
A drawing processor that stores in the frame memory display information of the color or brightness of each pixel for the second three-dimensional figure, and the display processor reads out the display information of the color or brightness of each pixel stored in the frame memory. A three-dimensional graphic display device, comprising: a display device that displays first and second three-dimensional graphics that have been subjected to hidden surface removal processing.