JPH01223580A - Method for displaying three-dimensional graphic - Google Patents

Abstract

PURPOSE:To normally display a segment stuck to a patch surface by setting the (z) value increased part to the extent to absorb the accuracy of a (z) buffer memory, and after the increased part is added to respective (z) values of the calculated contour line, executing the hidden-surface erasing processing. CONSTITUTION:The graphic data of an execution starting address 302 are fetched from a segment buffer 3 and converted to a coordinate system on a display 8. Next, an (z) value Z0 of the (z) buffer memory 7 of the part to display the graphic is read, a (z) value Zn to constitute a graphic is interpolated and calculated from the peak coordinates of the graphic. Next, when it is decided to be a segment graphic, a (z) value (Zn+DELTAZ) to substrate the Zn of the segment graphic in a viewpoint direction only by DELTAZ 304 is obtained, compared with the Z0 of the memory 7, and when the (z) value (Zn+DELTAZ) is to be at this way more, the Zn, which is the (z) value of the segment, is written in the memory 7, and simultaneously, the hidden-surface erasing processing is executed, the color information of the segment graphic is written into a frame memory 6 and the segment graphic is displayed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to hidden surface removal processing during three-dimensional display, particularly when line segments such as contour lines are displayed overlappingly on a three-dimensional image by hidden surface removal processing. The present invention relates to a suitable three-dimensional graphic display method.

[Conventional technology]

Examples of hidden surface removal processing when displaying conventional three-dimensional images include:
“Development of three-dimensional graphic systems” (PIXEL)
, March 1984 issue, P, 116-P, 122, by Ito). In this conventional example, a three-dimensional image is divided into polygons (
(so-called patch division), image processing is performed based on this polygon division, and hidden surface removal processing is performed.

FIG. 3 shows an example of polycon processing. When displaying a line segment (contour line) 21 superimposed on the cylinder 20 shown in FIG. 3(a), first, as shown in FIG. is a small plane called patch plane 23 to 28, and line segment 21 is a small plane called patch plane 23 to 28, and line segment 30 to
35, respectively. However, in this figure, the cylinder is approximated by a hexagonal prism, but in reality, processing is performed by approximating it to an n-sided prism where n>1.

Next, the hidden surface removal process compares the depth information of each point of the figures to be superimposed, leaving the pixels that are closer to the field of view, and erasing the pixels that are farther away. In this way, for the overlapping portion, only the pixels in the front are displayed.

[Problem to be solved by the invention]

The above conventional example has been described as an example of hidden surface removal processing using general figures that overlap each other. On the other hand, there are cases in which circles such as equal straight lines are drawn on a three-dimensional figure, and in order to process these equal straight lines using the conventional example described above, the processing method shown in FIG. 4 can be considered.

In FIG. 4, first, depth information (Z, ) for each point of a three-dimensional figure is read out one after another from the Z buffer memory (step 100). On the other hand, the equal straight lines are also divided into line segments using a type of patch division method, and only the end points of each line segment are given. Therefore, linear interpolation is performed from the two end points given for each line segment to each point of the three-dimensional figure, and depth information for the interpolated line segment (Z
n) is determined (step 101).

Next, for each point, a comparison is made between the corresponding Zo and Zn. If zo)zn, the three-dimensional drawing information is selected because Zo is in the foreground, and conversely, the isolinear depth information 2° is discarded. At this time, the corresponding zo coordinates of the three-dimensional figure are displayed. On the other hand, if z o < z n, it is assumed that Zn is in the foreground, and isolinear coordinates corresponding to Zn are displayed. In this case, display information of isolinear coordinates corresponding to Zn is stored on the frame memory as z.

It is necessary to write in place of the pixels of the corresponding three-dimensional drawing (step 103).

However, the above processing is ideal, and in practice, accurate hidden surface processing is difficult. The first reason is the capacity of the image processing processor, and the second reason is that it is necessary to perform floating point operations to process depth information stored in the z buffer, which reduces processing speed and However, this method is difficult to employ in practice, and calculation errors are likely to occur. If this causes an error, as shown in Figure 3 (C), when contour lines with hidden surface processing are displayed, the isolines that should be displayed as solid lines on the patch surface are missing and are displayed as broken lines (A). , or there may be a portion (B) that is not displayed at all.

SUMMARY OF THE INVENTION An object of the present invention is to provide a three-dimensional graphic display method that can properly display line segments stuck on a patch surface as described above without any display errors through simple processing.

[Means to solve the problem]

The purpose of the above is to display three-dimensional line segments with hidden surfaces removed.
Set a binary increment that can absorb the calculation accuracy of the graphics processor and the accuracy of the z buffer memory,
This is achieved by adding this increment to each binary value of the calculated isoline and then performing hidden surface removal processing.

[Effect]

The operator appropriately sets the increment of the Z value using an appropriate input means. As a result, the desired isoline can be easily brought to the foreground and displayed as a solid line, and since the calculation required for this is only a simple addition, there is no problem in processing speed even when using conventional heart means. do not have.

〔Example〕

An embodiment of the present invention will be described below. FIG. 2 shows an example of the configuration of a system to which the method of the present invention is applied. The central processing unit 1 that controls the entire system includes a system path 2.
A segment buffer that stores the graphic data 200 and coordinate transformation of the graphic.

Graphics processor that performs clipping, hidden surface removal processing, etc. 4. Keyboard 10. Dial 11° Input/output controller 9 that controls input/output devices such as tablet 12
, a memory 300 that stores control information for performing hidden surface removal processing according to the present invention is connected. The graphic processor 4 also has a frame memory 6 that stores color information in one-to-one correspondence with the screen of a display 8, and a binary value (
A z-buffer memory 7 for storing depth values) is connected thereto.

1 is a flowchart of a process illustrating an embodiment of the method of the present invention, which is executed by the graphics processor 4. In the figure, first, the graphics processor 4
When receiving the display start command from the central processing unit 1,
The graphic data 200 is read from the segment buffer 3, the normal hidden surface erasing process shown in FIG. When this series of display processing 500 is completed, the graphics processor 4
takes in the contents of the memory 300 in which control information is stored, checks the ΔZ valid/invalid flag 301, and carries out validation/invalidation of the ΔZ value (step 400). flag 30
If 1 is invalid, the process stops at step 400. At this time, the operator looks at the figure displayed on the display 8 and determines whether or not to draw the line segment figure (equiline) toward the viewpoint, and operates the dial 11 if he or she wishes to draw it toward the viewpoint. The input/output controller detects the input from the dial 11, writes it into Δ2 of the memory 300, and sets the Δ2 valid/invalid flag 301 to valid. Then, the graphic processor 4 detects that the Δ2 valid/invalid flag 301 has become valid in step 400 and proceeds to step 401, where the Δz304
, and the depth start address 302 and execution end address 303 of the segment buffer 3 that have been set in advance by the central processing unit 1, and in step 402, Δ
2. The valid/invalid flag 301 is changed to invalid, and the following three-dimensional figure display process is started.

First, in step 403, the graphic data at the execution start address 302 is fetched from the segment buffer 3, and in step 404, the coordinates are converted to the coordinate system on the display 8. Next, in step 405, z of the part where this figure is displayed
The binary value (Zo) of the buffer memory 7 is read out, and further, in step 406, the Z value (Zn) of the pixels constituting the figure is calculated by interpolation from the vertex coordinates of the figure. Next, in step 407, it is determined whether or not it is a line segment figure. If it is determined that it is a line segment figure, in step 409, the z,
Binary value (zn+
Δ2) is calculated and compared with ZO in the Z buffer memory in step 410 using this. If it is determined in step 411 that the Z value (zn+Δ2) of the line segment figure is closer, the line segment 2 At the same time, the color information of the line segment figure is written to the frame memory 6.
Write and write, and display the line segment shape. If it is a figure other than a line segment (area figure), the process proceeds to step 408, where Zn of the figure is compared with Zo of the z buffer memory 7, and step 4
Proceed to 11. In step 412, the address of the next figure data is determined and the address is the execution end address 303.
It is determined whether they match, and if they do not match, the process returns to step 403 and similarly displays the graphic data. If they match, return to 5TART.

The graphic processor 4 repeatedly executes the above processing until a new display activation command is received from the central processing unit 1.

〔Effect of the invention〕

According to the present invention, an operator uses an input device such as a dial to specify an arbitrary Δ2 value, without the intervention of a central processing unit, thereby moving the display of a line segment figure back and forth in the viewpoint direction. This makes it possible to display line segments stuck on a surface normally and at high speed.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of display processing showing an embodiment of the method of the present invention, FIG. 2 is a block diagram showing an example of a system to which the method of the present invention is applied, and FIG. 3 is an example of graphic data of a three-dimensional figure and its FIG. 4, which is an explanatory diagram of the display method, is a flowchart showing a general hidden surface removal processing method. 4...Graphic processor, 7...z buffer memory, 300...control information memory, 301...Δ
2 valid/invalid flag, 302... depth start address,
303... Execution end address, 304... Increment.

Claims (1)

[Claims] 1. Compare the depth coordinate value of the currently displayed figure stored in the z-buffer with the depth coordinate value of the newly displayed figure, and store the depth coordinate value of the figure data having the depth coordinate value closer to the viewpoint in the z-buffer. In the three-dimensional figure display method that performs hidden surface removal processing, for figures specified to perform incremental processing, the depth coordinate value of each point of the figure is A method for displaying a three-dimensional figure, characterized in that, after adding an increment value, hidden surface removal processing is performed by comparing the added value with the depth coordinate value of the figure being displayed. 2. Claim 1, characterized in that means is provided that allows an operator to set the constant increment value from the outside.
Three-dimensional figure display method described in Section 3.