JP3293157B2 - Point closed area search processor - 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 area search processing method for identifying whether a point is inside or outside a certain closed-loop figure in processing of a plane figure by a computer. .

[0002]

2. Description of the Related Art When a graphic is processed by so-called CAD or the like, a certain point exists in a closed loop formed by a straight line and a curve, or a point outside the closed loop. Need to be identified.

[0003] Such identification is usually processed as follows. That is, as shown in FIG. 2A, the curved part is replaced with a polygonal line, the closed loop is approximated by a polygon, and the angle between a specified point (black circle in the center of the figure) and each side of the polygon is determined. , The sides are counted in order, and the angle is measured positively when viewed from the point, for example, counterclockwise.

As a result, as can be easily inferred from the examples of FIGS. 2A and 2B, if the point is inside the closed loop (FIG. 2).
(a)), the sum of the angles is 2π, and if it is outside (Fig.
(b)) Since the sum is 0, the position of the point is identified by the sum of the angles.

[0005] Actually, due to an error in the calculation of the angle,
Since the sum generally does not exactly equal 2π or 0, it is determined, for example, whether the sum is greater than or less than π. According to this method, the curve portion of the closed loop is decomposed into broken lines,
Approximate the closed loop with a polygon, and for all its sides,
It is necessary to calculate an angle for each triangle formed by each side and the designated point, and the amount of calculation required for that is relatively large.

In order to perform approximation by a straight line, for example, as shown in FIGS. 2 (c) and 2 (d), a point inside the closed loop becomes outside the approximate polygon (FIG. The example (c)) and the reverse case (the example in FIG. 2 (d)) cannot be avoided, and appropriate processing for avoiding erroneous recognition in such a case is necessary.

[0007] On the other hand, considering a half line having a point as one end,
It is well known that if a point is inside the closed loop, the number of intersections between the half line and the closed loop is odd, and if the point is outside, the intersection with the closed loop is even or zero.

FIGS. 3 (a) and 3 (b) are diagrams illustrating this relationship by way of example. FIG. 3 (a) shows that the point is inside the closed loop and there are three intersections with the half-line. Since the point is outside, there are two intersections.

However, if an attempt is made to identify an area where a point is located by using this relationship, for example, as shown in FIG. 3 (c), a half line passes through a line segment of a closed loop element or an end point of a curve. Then, the number of intersections with each element becomes one, and the number of intersections is erroneous. In the case of the example in the figure, the number of intersections is counted as three, and it may be erroneously determined that the point is inside.

When the half line is tangent to the curve of the element of the closed loop as shown in FIG. 3D, there is only one intersection, and in the case of the example shown in the figure, the point is erroneously recognized as being inside. Furthermore, in practice, due to errors, closed loops are not always completely closed, and generally result in gaps between element line segments or curves, and when a ray passes through such a gap,
There are no intersections, and the number of intersections is incorrect.

Since there is a problem that it is necessary to take measures to prevent erroneous recognition in consideration of such conditions, the method of counting the intersections of the half-lines is a method that requires a relatively short calculation time. And has not been commonly used.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a closed point search processing method for a point in which a point area can be efficiently identified by the number of intersections between a half line and a closed loop.

[0013]

FIG. 1 is a flow chart of the processing showing the configuration of the present invention. The figure is a configuration of a point closed area search processing method, for a given plane figure, whether the position of the specified point is inside or outside the specified closed loop figure, for a half line having the specified point as one end, Each intersection between the line segment and the curve, which are the elements constituting the closed-loop figure, is obtained by a predetermined calculation, and an error value is provided according to the accuracy of the calculation when making a determination based on the number of the intersections.

On the condition that both the distance between the half line and the end point of any of the elements and the distance between the tangent of any curve passing through the designated point and the tangent of the curve are larger than the error value, Is selected (processing step 1).

The intersection is obtained by the calculation for the half line having the selected inclination (processing step 2). When the obtained number of intersections is odd, it is determined that the designated point is inside the closed loop, and when it is not odd, it is outside (closed).

[0016]

According to the processing method of the present invention, the inclination of the half line can be selected so as to avoid misinterpretation of intersections due to the limit of calculation accuracy and unusual intersections that may misrecognize the number of intersections. Since the area where the designated point is located is identified by the number of intersections, accurate identification can be performed with a relatively small amount of calculation.

[0017]

FIG. 4 is a diagram showing an example of a detailed processing flow of the present invention. First, in processing step 10, a tangent line passing through a designated point is determined for each curve of the element of the designated closed-loop figure. Determine the coordinates of the point of contact.

In processing step 11, a half-line having the designated point as one end is set, and its inclination is set to be as convenient as possible for calculation, such as, for example, first horizontally rightward, and then vertically upward. I will decide.

When a semi-line having a certain inclination is selected in a predetermined order, in step 12, the end points of the respective elements of the closed loop and the distance between the contact point obtained in step 10 and the half-line are sequentially calculated. When the distance to one end point or contact point is calculated, the distance is compared with a predetermined error value in processing step 13.

If the distance is not larger than the error value, the inclination of the currently selected half-line is determined to be inappropriate, and the process returns to the processing step 11 to repeat the processing with the next selected inclination. This error value is set based on the accuracy of the intersection calculation performed later, and when the intersection of the half line coincides with the end point, the calculation result may be near the end point or pass through the gap between the end points It is possible to remove the inclination of such a half line including the case where there is a possibility. The same applies to the relationship with the contact.

If the distance is greater than the error value, it is identified in processing step 14 and the processing from processing step 12 is repeated for all elements of the closed loop. As described above, when an appropriate inclination of the half line is determined, an intersection between the half line and each element of the closed loop is obtained in processing step 15, the number of intersections with the element is accumulated in processing step 16, and in processing step 17, The above processing is repeated until all the elements are identified and processed.

When processing of all elements is completed, processing step 18
Then, it is determined whether or not the total number of accumulated intersections is an odd number. If the total number is an odd number, a result of determination is made in processing step 19 that the area of the designated point is inside the closed loop.
Or, in the case of an even number, a determination result is issued that the area of the designated point is outside the closed loop.

FIG. 5 shows an example of a point area search by the above processing. First, a horizontal half line is used as a trial. In the case of FIG. 5 (a), a horizontal half line corresponds to the exclusion condition. Therefore, when the intersection with each element (shown by adding 〜 in the figure) is calculated, there is one intersection with each element, and the intersection is 0 with the other elements, and the cumulative total is 2. It is determined that the total number of intersections is even and the designated point is outside the closed loop.

In the case of FIG. 5 (b), the first horizontal half-line passes through the closed loop elements and endpoints and is discarded as meeting the exclusion condition. Next, when the line is rotated by π / 2 to make an upward vertical half line, the intersection with each element is calculated because there is no exclusion condition. Since there is only one intersection with the element, the total number of intersections is an odd number. The designated point is determined to be inside the closed loop.

[0025]

As is apparent from the above description, according to the present invention, in regard to graphic processing by a computer, the method of using the number of intersections between a half line and a closed loop makes it possible to identify a point area accurately in a short calculation time. Therefore, there is a remarkable industrial effect of improving the processing efficiency of graphic processing.

[Brief description of the drawings]

FIG. 1 is a flowchart of a process showing a configuration of the present invention.

FIG. 2 is a diagram illustrating a conventional method.

FIG. 3 is a diagram for explaining a method based on intersections of half lines;

FIG. 4 is a flowchart of a process according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a processing example of the present invention.

[Explanation of symbols]

 1-3, 10-20 processing steps

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-64081 (JP, A) JP-A-61-213976 (JP, A) JP-A-2-130686 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G06T 7/60 G06T 11/40

Claims (1)

(57) [Claims] 1. A closed-area search processing device for a point which determines whether the position of a specified point is inside or outside a specified closed-loop figure for a given plane figure, wherein the specified closed-loop figure is formed from the specified points. Means for calculating all the tangents to the curve which is the element, calculating the coordinates of the contact point with a predetermined accuracy, a half line having the specified point as one end, and the end point of the element constituting the closed loop graphic, or the element is If it is a curve, the distance between the end point and the coordinates of the contact point of the element is determined with the predetermined accuracy, and a half line in which the distance is larger than an error value set in advance corresponding to the predetermined accuracy is determined. Means for selecting, obtaining all the intersections of the selected half-line and the elements constituting the closed-loop figure, and accumulating and storing the number of the intersections in the storage means; Identify whether the total number of intersections is odd and Means for determining that the designated point is inside the closed-loop figure if the number is a number, and that the designated point is outside the closed-loop figure if the number is not an odd number. apparatus.