JPS62168282A - Graphic drawing system - Google Patents

Abstract

PURPOSE:To prevent the apex of a polygon formed by connecting many segments, from becoming indistinct, by rewriting it forcibly as a calescence point, when the end part of the segment is blank, and always setting a connecting part of the segment and the segment, as the calescence point. CONSTITUTION:.When a broken line for displaying a quadrilateral ABCD consists of, for instance, a full line of 4 bits and a blank of 4 bits, a prescribed value Nmin=4 is set in a comparator 22. When the end part of the sides AB goes to <=4 bits, an output of the comparator 22 becomes '1' and irrespective of an output of a register 14, a data of a calescence point is written forcibly in a frame buffer 7. Accordingly, the apex B is always displayed by a bent part of a full line. In a downcounter 21, length of a long axis of the next, for instance, sides BC is written, by a count end of the sides AB, the operation is executed in the same way, and the apex C is displayed by a bent part of a full line.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for displaying line drawings on a display, and in particular, to clearly display figures when drawing polygons using broken lines, chain lines, etc. It is related to a graphic drawing method that can be used.

[Conventional technology]

When drawing a line segment on the screen of a display device such as a cathode ray tube (CRT), whether to display it as a solid line or as a line that includes a blank space on the line segment, such as a broken line or chain line, depends on the This is done depending on whether or not the data of each pixel is completely written into the image memory that stores image data as a bright spot.

FIG. 3 shows the configuration of a conventional graphic drawing device to which the present invention is applied. In the figure, a central processing unit (CPU) 1 is connected to each peripheral circuit via a path 2, and controls the operation of the entire system. The main memory 6 stores system programs and the like, and outputs them in response to address designations from the CPU 1. The image memory 4 stores data on figures to be displayed, and the line segment generation circuit 5 generates lines representing figures such as polygons based on the data in the image memory 4 under the control of the CPU 1. minute data is generated as a series of pixels. The line segment drawing circuit 6 performs control to draw generated line segments depending on whether they are solid lines, broken lines, or the like. The generated line segment is written into the 7-frame buffer 7 and held as data for one screen. The display (CRT) 8 is not a cathode ray tube, etc., and reads out the data of 7 frames x 7 a 7 according to the scanning of the screen.
Display shapes on the screen.

FIG. 4 shows the configuration of a conventional line segment drawing circuit. The up counter 11 is a counter that counts a predetermined value, and counts distributed pulses of pixels forming a line segment. The lookup table 12 stores data on solid lines, broken lines, etc., and the data on these line segments is read out using the count value of the counter 11 as an address. The line type selection register 13 generates an address based on instructions from the CPU 1 and inputs it to the lookup table 12, whereby the line type output from the lookup table 12 is selected. The register 14 temporarily holds the output data of the look-up table 12 and outputs it in response to the line segment distribution pulse. The output of register 14 is 7 frame buffer 7.
For example, in the case of a solid line, all the pixels are written as bright spots in the 7th frame 7a7, and in the case of a broken line, bright spots and blanks are written alternately for several bits at a time. FIG. 5 is an example of a figure drawn by the apparatus shown in FIGS. 3 and 4, and illustrates the case where four feed shapes ABCD are displayed by broken lines.

[Problem that the invention seeks to solve]

In the figure illustrated in FIG. 5, which is displayed by a conventional figure drawing device, there is no bright spot in the part corresponding to the apex of the four-way shape ABCD displayed by the broken line, and therefore the position of the apex of the figure is It may become unclear.

When drawing a line segment, as is clear from the configuration of the line segment drawing circuit shown in FIG. This is because the process is performed using only the information about the number of the pixel.

As described above, in conventional image drawing devices, when displaying a polygonal figure, the vertices are not always displayed as bright spots, and therefore, the problem is that the vertices of the polygon cannot always be clearly defined. there were.

[Means for solving problems]

In order to solve the problems of the prior art, the figure drawing method of the present invention includes a line segment generating means and draws figures by line segments consisting of alternating repetition of bright spots and blank spaces of an arbitrary number of bits. The apparatus includes the following means.

A counter is provided to set the length of the long axis of the line segment at the start of each line segment and count down by the line segment distribution pulse.

It is equipped with a comparator and checks the contents of the counter and generates an output when the value is below a predetermined value.

It includes an OR circuit and generates line segment data by adding the output of the comparator and the output of the line segment generating means.

[Effect]

In the figure drawing method of the present invention, it is determined that the remaining length obtained by subtracting the length of the drawn line segment from the given length is shorter than the length of the blank part, and the final part of the line segment is When is blank, it is forcibly rewritten as a bright point, so the connection between line segments will always be a bright point, and therefore the vertices of a polygon formed by connecting many line segments will be unclear. Never.

〔Example〕

FIG. 1 shows the configuration of a line segment drawing circuit in an embodiment of the graphic drawing method of the present invention, in which the same parts as in FIG. 2 are designated by the same numbers, and 21 is a down counter;
22 is a comparator, and 23 is an OR circuit.

In the tJ111 diagram, the down counter 21 is set to the length of the long axis of the line segment at the starting point of the line segment, and is counted down in accordance with the distribution pulse of the line segment. Comparator 22
compares the value of the counter 21 with a constant value Nm1n, and generates an output of 91m when the value of the counter 21 becomes smaller than the constant value Nm1n.

On the other hand, up counter 11. Lookup table 12
．． Line type selection register 13. The circuit consisting of the register 14 is the same as the circuit shown in FIG. Output.

The output of the register 14 and the output of the comparator 22 are added together via an OR circuit 23, and the output is sent to the frame buffer 7.
A line segment is written into the 7-frame buffer 7 by providing the 2-bit enable signal of the pixel to the 7-frame buffer 7. Data in the frame buffer 7 is read out as the CRT 8 is scanned, and graphics are displayed on the screen of the CRT 8.

FIG. 2 shows an example of a figure drawn by the method of the present invention, and illustrates a case where four feed shapes ABCD are displayed by broken lines.

In FIG. 2, when the broken line indicating 4-feed type ABCD consists of, for example, a 4-bit solid line and 4-pit blanks, it is assumed that Nm1n = 4 is set in the comparator 22.

When the last part of side AB becomes 4 bits or less, the output of comparator 22 becomes @1'' and register 1
Regardless of the output of 4, the bright spot data is forced to 7.
It is written in frame 7a7. Therefore, vertex B is always displayed as a bent part of a solid line. When the count of side AB ends, the length of the next side, for example, the major axis of BC, is written in the down counter 21, and the apex C is displayed by a solid line bend in the same manner.

In this way, in the method of the present invention, even if a polygonal figure is displayed by a line including a 9n part such as a broken line, each vertex is always displayed with a 9 at the bend of the solid line, so the vertex becomes unclear. There isn't. When changing the line type, the contents of the lookup table 12 can be changed according to the line type desired to be displayed, and the method of the present invention can therefore be applied to any line type.

〔Effect of the invention〕

As explained above, according to the method of the present invention, even when a polygon is displayed in a graphic drawing device using a line type that includes blank spaces such as a broken line, each vertex is always displayed with a bend of a solid line, and the vertex is never unclear.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a line segment drawing circuit according to an embodiment of the method of the present invention, FIG. 2 is a diagram illustrating a figure drawn by the method of the present invention, and FIG. 3 is an example of the configuration of a figure drawing device. FIG. 4 is a diagram showing the configuration of a conventional line segment drawing circuit, and FIG. 5 is a diagram showing the configuration of a conventional line segment drawing circuit. FIG. Line type selection register 14...Register 21...Down counter 22...Comparator 26...OR circuit Patent applicant Fanuc Co., Ltd. agent Patent attorney Gobe Tamamushi (2 others) Line segment of the present invention Structure of tank heavy circuit Day 1 Figure 1 Diagram illustrating the figure constructed by the method of the present invention III of the drawing! Figure 3

Claims (1)

[Scope of Claims] Line segment generating means is provided for counting distribution pulses for a line segment and using the counted value as an address to read line segment data stored in a memory. In a figure drawing device that draws polygons using line segments that alternate with blank spaces, the length of the major axis of each line segment is set for each drawing of the line segment, and the length of the long axis of the line segment is set by the line segment distribution pulse. a comparator that generates an output when the content of the counter is equal to or less than a predetermined value; and a comparator that generates line segment data by adding the output of the comparator and the output of the line segment generating means. A figure drawing method characterized by