JPH02115986A - Method for generating control of grid shape range of points data - Google Patents

Abstract

PURPOSE:To reduce a processing quantity compared with a method to generate a segment at every triangular unit by a generating a contour segment in rectangular unit consisting of four pieces of data in the plotting of the contour of range of points data distributed in grid shape. CONSTITUTION:A processing to generate the segment of the contour at every rectangle consisting of the four pieces of data distributed in the grid shape is performed. In other words, the number of intersections of the circumference of the rectangle consisting of the four pieces of range of points data distributed in the grid shape with the height of a prescribed contour from a memory 13 in which the height of the contour is stored is found. A processing only to perform whether or not one or two segments of the contour are generated is performed according to the number of found intersections and an intersection pattern. In such a case, the crossing of the contours with different height is prevented from occurring by identifying the intersection pattern by setting a diagonal line in a specific direction for every rectangle. In such a way, it is possible to reduce the processing quantity to generate the segment compared with the method to perform the processing at every triangle.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a contour line generation method for grid point sequence data.
In particular, it relates to a general-purpose contour line drawing method that can reduce the amount of processing.

[Conventional technology]

In conventional graphic processing using computer software, there is no simple and universal contour drawing algorithm for two-dimensional finite difference method data, and a method is often used in which all quadrangles surrounded by adjacent grid lines of the finite difference method are divided into triangles. Ta.

That is, the conventional drawing method is, for example,
As described in Japanese Patent No. 380, a process is performed for point sequence data to generate a contour line segment for each triangle made up of data of three points. In this method, 3D data subjected to surface interpolation is read from a 3D point sequence data memory, the 3D data is divided into triangles by a triangular mesh generator, and the contents corresponding to the vertices of each triangle are stored in memory. I read it out again and use the intersection calculator to calculate the intersection. Then, search for contour values and create continuous contour lines.

[Problem to be solved by the invention]

However, the method of dividing into triangles has a problem in that the contour lines within the quadrilateral are broken. Further, in such conventional methods, no consideration is given to the process of generating contour line segments for each rectangle made up of four points for point sequence data distributed in a grid state. Therefore, the processing for each triangle is 2 times the processing for each rectangle.
This required twice as much processing, resulting in a large amount of processing for segment generation.

The purpose of the present invention is to solve such conventional problems and to provide a contour line generation method for grid point sequence data that can reduce the amount of processing for segment generation compared to the method of processing each triangle. It is about providing.

[Means to solve the problem]

In order to achieve the above object, the contour line generation method of grid point sequence data according to the present invention generates segments from two-dimensional point sequence data distributed in a grid pattern and having heights and contour line height data. , in a contour line generation method that connects contour lines formed by the segments, generates the connected contour lines using a polygonal line generator, and displays the contour lines on a graphic device, when the segments are automatically generated by a program. For each rectangle consisting of four points of data, the number of different intersections on the periphery is checked, and when the number of intersections is less than 2, contour line segments are not generated, and when the number of intersections is 2, the two intersections are generated except in exceptional cases. Generates a contour line segment with the start and end points as the starting and ending points, and if the number of intersections is more than 2, generates one contour line segment unless the data values of all four vertices match the contour line height, and the data values of three vertices match the contour line height. If it matches the contour line height, a segment is generated whose start and end points are the two diagonal vertices.

Also, if two segments can be generated for one rectangle, then for the two triangles created by dividing the rectangle into two,
The feature is that a segment is generated that passes through each intersection.

[For production]

In the present invention, a process is performed to generate contour line segments for each rectangle made up of four points on point sequence data distributed in a grid pattern. That is, for a rectangle made up of four points of point sequence data distributed in a grid, the number of intersections with a predetermined contour line height is determined from a memory that stores the rectangle's circumference and contour line height.

Depending on the number of intersections and the intersection pattern, one, two, or no contour segments are generated. In this case, by identifying an intersection pattern for each rectangle based on a diagonal line in a specific direction, contour lines of different heights are prevented from intersecting. This makes it possible to reduce the amount of processing required to generate segments compared to a method in which processing is performed for each triangle.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a block diagram of a contour line drawing processing device showing one embodiment of the present invention.

In FIG. 4, 11 is a point sequence data storage memory for storing two-dimensional point sequence data that is distributed in a grid pattern and each has a height, and 12 is a point sequence data storage memory for reading data from the point sequence data storage memory 11. A data reading unit 13 is a contour line height storage memory that stores data on the heights of contour lines to be drawn arranged in a plane; 14 is a processing unit which is the center of the present invention, and is read by the data reading unit 12; A segment generation unit calculates the intersection between the generated coordinate values and a predetermined contour line height from the memory 13 and generates contour line segment coordinates; 15 is a segment storage memory for storing the generated segments; 16 is a segment storage unit An equi-level linking unit extracts the segment coordinates stored in the memory 15 and connects the segments to create an equi-level unit; 17 generates a polygonal line to output the connected segment group to the graphic device 18; A polygonal line generation unit 18 is a graphic device for displaying the generated polygonal line.

In the present invention, a processing device having such a configuration can:
4 automatically by the program within the segment main section 14.
A segment is generated for each rectangle made of point data, and these segments are connected to create parts corresponding to the ridges and valleys of the data, that is, equilevels that pass through the grid points.

FIG. 2 is a diagram showing an example of contour lines drawn by the apparatus shown in FIG. 1.

In Figure 2, e, + is the part that satisfies the height of the equigrade of the data value > solid line, and e, - is the part that satisfies the height of the equigrade of the solid line, conversely, 0 is the data value =
It is the part that satisfies the height of the solid line, and ・ is the intersection point, and here cases 1 to 4 (for these,
(Explained in FIG. 3) are shown. Further, in FIG. 2, an example of the equivalent class having a higher height than the illustrated solid line equivalent class is shown by a broken line.

Here, three solid line equilevels are shown: the lower left part, the center part, and the upper right part. In this case, a case in which two intersections with the lower left equal high-level and two intersections with the central equal high-level exist in the same rectangle 4 is called a two-segment generation case. Note that even for a rectangle with three intersection points, two segments may be generated. Furthermore, the case where the central equilevels intersect at two of the four vertices in one rectangle 1 is called a 22-vertex exception case. Furthermore, the four intersections on the upper right are the intersections of vertices that have the same height as the constant height of the solid line, and since these are included in one rectangle 3, this is called a 4-vertex case. .

In addition, the rectangle below it is called a three-vertex case, in which three of the four vertices in one rectangle 2 are at the same height as the equivalent height, and between two of them is drawn. This direction of equal height is called the reference diagonal direction.

Next, we will define each case.

(a) II’2 Vertex exception case j1 is.

When the data values at two vertices facing each other across the diagonal line of the standard match the equi-height height and those two vertices intersect), and the data values at the other two vertices are both larger (or smaller) than the equi-height height. To tell.

(b) The li'3 vertex case J2 refers to a case where the data values at three vertices match the equi-height heights (three vertices intersect).

(c) [r44 top case” 3.

This refers to the case where the data values at all four vertices match the equal height heights (the four vertices intersect).

FIG. 3 is a diagram showing an intersection pattern between a rectangle and equal heights.

In FIG. 3, rectangles numbered 1 to 4 correspond to those in FIG. 2, where 1 is the two-vertex exception case,
2 is a 3-vertex case, 3 is a 4-vertex case, and 4 is a case for generating 2 segments. There is only one case of the 4-vertex case 3 and the 2-vertex exception case 1, but there are two cases of the 3-vertex case 2: a segment from the upper left to the lower right, and a segment from the upper right to the lower left. In addition, in case 4 of 2-segment generation, 5
There are two cases. In other words, as in the above two cases, two segments are drawn in parallel from the top left to the bottom right, but
The left side is when the enclosed part is higher than the surrounding area, and the right side is when the enclosed area is lower than the surrounding area. Also, as in the three cases below, two segments are drawn in parallel from the upper left to the lower right, but one of the segments is missing, and the two parallel segments intersect at one of the three. This is the case.

The 12 rectangles in the upper right of FIG. 3 each have two intersections with the equi-high grade at positions that are not vertices, and segments are drawn from the upper right to the lower left, from the upper left to the lower right, and in the vertical and horizontal directions.

The ten rectangles shown in the lower right of FIG. 3 all have one to four vertices of equal height.

This includes 2-vertex exception case 1 and 4-vertex exception case 3.

FIG. 1 is a processing flowchart of the segment generation unit in FIG. 4.

The segment generation process will be explained in detail with reference to FIG. 1 while referring to FIGS. 2 and 3.

It is now assumed that point sequence data distributed in a lattice pattern is stored in the memory 11, and high-grade heights such as those to be drawn are stored in the memory 13. First, input a predetermined equivalent height from the memory 13 (step 101), then input the height from the memory 11.
Data for one rectangle is extracted from the data read through the data reading section 12 (step 102). Calculate the intersections between this rectangle data and the equivalent height, and check the number of different intersections of the rectangle (steps 103 and 10).
4). When the number of intersection points is less than 2 (that is, when there is 1)
There are three cases: , the number of intersections is 2, and the number of intersections is greater than 2 (that is, 3 and 4).

(i) When the number of intersections is 2: In this case, contour line segments are not generated, and if it is not the end of the data, quintic rectangular data is extracted (steps 111 and 102), and the process is repeated. Also,
If it is the end of the data, the process ends (step 11
1).

(ii) When the number of intersections = 2 In this case, ``Except for the two-vertex exception case j1, generate a contour line segment with the two intersections as the start and end points, and store this in the memory 15 (step 108).

Thereafter, the same process as in the case where the number of intersections is <2 is repeated (steps 111 and 102).

(iii) When the number of intersections>2 In the rf4 vertex case J3, no segment is generated (step 106). In addition, "In the case of 3 vertices case J2, the data values at the 3 vertices match the equi-height heights. In this case, a segment whose start and end points are the 2 vertices on the diagonal is generated and this is Store (step 110).

In other cases, it corresponds to case 4 of "Generation of 2 segments", and 2 segments are formed by dividing the rectangle into 2 along the standard diagonal line.
For each of the three triangles, a segment passing through the intersection is generated and stored (step 109). That is, in this case, two segments are generated for one rectangle. below.

The same process as in the case where the number of intersections is 2 is repeated (steps 111 and 102).

By the way, in the two-vertex exception case j1, the second
As shown in Figure 1, when generating contour segments,
It can be seen that when other equivalent levels indicated by broken lines are displayed simultaneously, they intersect. This occurs in relation to the diagonal direction of the rectangle division in case 4 of "Generation of 2 Segments". This is because by examining the intersection patterns shown in FIG. 3 one by one, it can be seen that only the two-vertex exception case j1 has a possibility of intersecting with other equal-high-level cases.

In this embodiment, contour line segments can be generated in units of rectangles for point sequence data distributed in a grid pattern, so the amount of processing can be reduced compared to the case where processing is performed in units of triangles. The approximate amount of reduction is shown below.

[1] Compared to segment generation processing performed on a triangular basis,
The processing amount of segment generation can be reduced to about ⅔.

(Segment generation processing amount) Valve (number of data units) * (
In the calculation formula for (number of intersection points per data unit), in this example, (number of data units) can handle two triangles in one rectangular unit, so the processing amount is halved, and (number of data units) Since the number of intersection points calculated is proportional to the number of sides of a data unit, the number of intersection points is 4/3 for a rectangle compared to a triangle.

Therefore, the ratio of throughput is (1/2) Monkey (4/3) = 2/3.

[2] Compared to segment generation processing performed on a triangular basis,
The number of generated segments can also be reduced by about 2/3. Therefore, the number of equal-level plots can also be reduced to about 2/3.

In other words, to explain this using Figure 3, since it is rare for the equivalent height to match the data value of the vertex of the rectangle, 1
It is sufficient to consider only the patterns in the top three rows of the diagram. The number of segments here is 16 in total. On the other hand, if the rectangle is divided along diagonals in a certain direction and processed into two triangular units, the number of segments will be 24. Therefore, in general, the ratio of the number of plots of equal grade is the ratio of the number of segments, so 16/24=2/3.

〔Effect of the invention〕

As explained above, according to the present invention, contour line segments can be generated in rectangular units consisting of data of four points in contour line drawing of point sequence data distributed in a grid pattern, so when generating segments in triangular units, In comparison, it is possible to reduce the amount of processing.

[Brief explanation of drawings]

FIG. 1 is a processing flowchart of the segment generation unit showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of contour line drawing by the processing of FIG. 1, and FIG. FIG. 4, which is a diagram showing an intersection pattern with height, is a block diagram of a contour line drawing processing device showing an embodiment of the present invention. 11: point sequence data storage memory, 12: data reading section,
13: Equal grade height storage memory, 14: Segment generation section, 15: Segment storage memory, 16: Equal grade connection section,
17: Broken line generator, 18 Nigella hook device. Fig. +・,・Data value> Equivalent height of solid line 0 ... // wm //ku intersection (shown only for cases 1 to 4) Fig.

Claims (1)

[Claims] 1. Generate segments from two-dimensional point sequence data distributed in a grid pattern and having heights and contour line height data, connect the contour lines formed by the segments, and use a polygonal line generator to generate the above-mentioned connected lines. In a contour line generation method that generates contour lines and displays the contour lines on a graphic device, when automatically generating the above segments by a program, the number of different intersection points on the periphery is calculated for each rectangle consisting of four points of data. When the number of intersection points is less than 2, a contour line segment is not generated; when the number of intersection points is 2, a contour line segment with the two intersection points as the start and end points is generated, except in exceptional cases; when the number of intersection points is greater than 2, a contour line segment is generated. , unless the data values of all four vertices match the contour line height, a contour line segment is generated, and if the data values of three vertices match the contour line height, two diagonal vertices are used as the start and end points. If two segments can be generated for one rectangle, a lattice point sequence that is characterized by generating segments that pass through the intersection of two triangles created by dividing the triangle into two along the diagonal line. How to generate data contours.