JP2897541B2 - Closed figure extraction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a closed figure extracting method,
In particular, layout CAE (Computer Aided Engineering)
Of CAD (Compu
ter Aided Design), and relates to a closed figure extraction method of a pattern maintenance method for a conductor region having an area or a prohibited area.

[0002]

2. Description of the Related Art In a conventional closed figure extraction method, a line segment sharing each end point is sequentially traced for an independently given line segment group, and when a branch point is reached, the line segment found first is traced. Tracing is performed with priority, and tracing is not performed for other branch line segments. For example, if a group of line segments as shown in FIG. 4 is given,
The closed figure 300 is detected by sequentially tracing. In addition, while tracing, a flag is set on the traced line segment so that the trace is not traced again. Such a sequence is repeated until there is no line segment without a flag.

In FIG. 4, a line segment group 301 for which the first tracing has not been performed does not form a closed figure. Canceled.

[0004]

In the above-described conventional closed figure extraction method, when a branch point exists in a given line segment group, only one of the branch points is enabled and traced. Some closed figures could not be detected. Therefore, the data entry person carefully entered the data so that the computer could understand. Further, there is a drawback in that a concave figure deformed as shown in FIG. 2 cannot be handled as a donut-shaped closed figure expression in which another closed figure is included in the closed figure.

[0005]

A closed figure extracting method according to the present invention comprises the steps of extracting an arbitrary line segment from a plurality of line segments given the coordinates of both end points and storing one of the line segments as a starting point;
A procedure to repeatedly search for another line segment connected to the other end point, trace the line segments in a chain, set a traced flag at the time of tracing, and there are multiple line segments sharing the end point In this case, the procedure to select the line segment that makes the largest angle with the previous line segment, the procedure to stack other line segments, and the procedure to close the traced line when returning to the starting point by tracing Procedure to output as constituent sides, procedure to trace similarly with stacked line segment as start line segment, and procedure to cancel stacking line segment with traced flag set It is comprised including.

[0006]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart of an SPD (Structur Program Diagram) format showing an embodiment of a closed figure extracting method according to the present invention.

FIG. 1 shows a flow chart of the algorithm proposed by the present invention. The algorithm of FIG.

When a group of line segments as shown in FIG. 2 is given, an arbitrary line segment is extracted first. Here, in order to proceed the subsequent trace processing in a counterclockwise direction, the lower left end point is extracted as much as possible. Things. For this purpose, a line segment including the minimum y coordinate is first obtained, and a line segment with a smaller angle with the horizontal line is further selected. In FIG. 2, the line segments 101, 112, and 102 are candidates as the line segments including the minimum y coordinate. However, since the line segment 101 has a small angle with the horizontal line, this is selected as the start line segment. Next, start point is endpoint 1.
And the line segment 102 sharing the end point 2 is detected. Further, line segments sharing the opposite end point 3 are detected, and there are line segments 103, 107, and 108. Among these, the line segment 103 and the line segment 107 have the largest angle with the line segment 102, but the line segment 103 having a shorter length is adopted. Therefore, a line segment sharing the end point 4 is searched for as a trace. At this time, the line segment 107 and the line segment 108 are stacked. When tracing is continued in this manner, the line segment 107 is reached. However, since a similar branch also exists at the end point 3, if the same rule as above is applied, the line segment 108 is selected as a trace line segment, and Line segment 102 and line segment 103 are stacked. Thus, the line segment 110 is reached, the start point 1 is reached, and the closed figure 200 is output. At the time of output, a line segment forming a side of the closed figure is set with a flag for expressing it.

Next, again from the stacked line segments,
The detection of the closed figure is started, but since the above-mentioned flag shows that the line segment 107, the line segment 108, the line segment 102, and the line segment 103 have already been detected as the closed figure, it is determined from the candidates as the start line segment. Is removed, and the process ends because the stack is empty.

As another example, the case of FIG. 3 will be described.
As a phase in which a graphic as shown in FIG. 3 is input, first, the input person first inputs a line segment 120, a line segment 121, a line segment 122, and a line segment 123.
After creating the closed graphic composed of the following, an attempt is made to modify the graphic so as to increase the size of the graphic. At this time, the line segment 122
There is no problem if is deleted, but since the entity as a closed figure does not matter whether the line segment 122 exists or not,
There is no problem if the drawings are left as they are. First, the end point 20 is selected as the starting point, and the segment 12 is selected as the starting segment.
0 is chosen. The tracing is started to reach the line segment 121, where the line segment 124 is stacked, and the trace is advanced at the line segment 122. Further, the line segment 126 is stacked,
Since the start point 20 is reached at the line segment 123, the closed figure 201
Is output.

Next, tracing is started from the line segment 124 in the stack with the start point as the end point 22. Proceeding to the line segment 125 and the line segment 126 and reaching the end point 23 which is a branch point, the line segment 123 is stacked and the trace is restarted at the line segment 122. At this stage, since the end point 22 which is the start point is reached, the second closed figure 202 is output.

Although the remaining stack includes the line segment 123 and the line segment 126, since the flag as a component of the side of the already output closed figure is set, the line segment as the start line segment is set. The process ends without being a candidate.

[0014]

As described above, according to the closed figure extracting method of the present invention, when a plurality of line segments share an end point, by stacking the branch points, a figure which can be a closed figure is not leaked. It is possible to detect. Furthermore, by providing a method for uniquely determining which of the plurality of line segments in the branch is to be traced and which is to be stacked, it is possible to eliminate contingency at the time of execution. Also, in the extraction of the trace target in the branch, the condition that the angle with the immediately preceding line segment is the maximum and the method of determining the line segment at the start of the trace output the closed figure as little as possible. It is possible to consider the information of the obtained line segment group as a closed figure without leaking.

[Brief description of the drawings]

FIG. 1 is an SP showing an embodiment of a closed figure extracting method according to the present invention;
It is a flowchart of D (Structur Program Diagram) format.

FIG. 2 is a diagram illustrating an example of an operation in the closed figure extracting method according to the embodiment;

FIG. 3 is a diagram illustrating an example of an operation in the closed figure extracting method according to the embodiment;

FIG. 4 is a diagram showing an operation in a conventional closed figure extracting method.

[Explanation of symbols]

 1 to 25 Endpoint 101 to 126 Line segment 200 to 300 Closed figure 301 Line segment group

Claims (1)

(57) [Claims] 1. A procedure for extracting an arbitrary line segment from a plurality of line segments given the coordinates of both end points and storing one of the line segments as a start point, and searching for another line segment connected to the other end point. Repeat the steps to trace the line segments in a chain, to set the traced flag at the time of tracing, and to make the angle between the line segment in front when there are multiple line segments sharing the end point the most. A procedure to select a line segment to be enlarged, a procedure to stack other line segments, a procedure to output a traced line segment as a closed figure when returning to the starting point by tracing, A closed figure extracting method characterized by comprising a procedure of similarly performing a trace using a line segment as a start line segment and a procedure of canceling a stuck line segment having a traced flag set.