JPH0490080A - Method and device for processing hidden line in two-dimensional cad system - Google Patents

Abstract

PURPOSE:To easily execute hidden line processing by simple operation restricted only to the specification of front and rear elements by forming a closed area by outermost side elements out of front side elements and changing rear side elements included in the closed area to hidden line expression. CONSTITUTION:A closed area is stored by extracting front side elements and sorting the outermost side elements and a part shown by a slash part in Fig.(a) corresponds to the closed area on a two-dimensional plane. Then, a line of rear side elements is divided by the closed area. The state of this case is shown in Fig.(b) and the line of the rear side elements (2) is divided by the closed graphic (1). In the case of processing the inside of the closed area in the counter- clockwise direction e.g., the left side elements of respective intersecting points are deleted. The above processing is continued until the rear side elements disappear to easily complete hidden line processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for performing hidden line processing on a back side element when a drawn figure has a front side element and a back side element in a two-dimensional CAD system, and the method thereof. Regarding equipment.

[Prior Art] Conventionally, CAD systems that have been able to perform hidden line processing to represent elements on the back side of drawings with dashed lines have been developed into 3D database CAD systems that have 3D attributes such as wireframes, surfaces, and Sonorado. It was limited. This hidden line processing was performed by modeling using three-dimensional attribute data. By the way, in a CAD system aimed at creating drawings such as architectural drawings, the most important requirements are the drawing function and responsiveness, so the amount of 3D attribute data for modeling is too large to have. is the current situation. Therefore, in two-dimensional CAD, hidden line processing involves deleting lines or making them broken lines using other editing functions.

9 and 10(a) and 10(b) show the operation of hidden line processing and an example of the drawing at that time.

To explain this, in the hidden line processing menu, specify the boundary 1 of the drawing on the system display screen (#
21). This instruction uses a mouse etc. to move the cursor to the border 1
This can be done by positioning and clicking. Next, boundary 2 is designated (#22). After that, select all the back side elements #23 #24) and perform hidden line processing #25)
, check whether there is a next process <#26), and if there is a next process, return to #21. By hidden line processing, the line between boundary 1 and boundary 2 is deleted as shown in FIG. 10(b).

The concept of the hidden line processing method in the system using the above operations is shown in Figures 11 and 12. The former is a three-dimensional CA
Calculations are performed based on three-dimensional attributes between data in case D, and the latter shows the case of two-dimensional CAD. FIG. 13 is a flowchart of hidden line processing in the two-dimensional CAD shown in FIG. 12. In this process, the intersection with the boundary is calculated (#31), and the line of the back side element is divided into three parts.
32 ), delete the second line or make it a dashed line (
83B).

This process is performed for each boundary element and each back side element.

[The subject that the invention sought to solve] As described above, conventional hidden line processing has complicated operating procedures,
In particular, 2D CAD does not have 3D data, so it cannot be achieved with a one-touch operation.

The present invention solves the above problems and uses two-dimensional CAD.
The object of the present invention is to provide a method and apparatus that can easily perform hidden line processing in a system with simple operations.

Means for Solving Two Problems] In order to achieve the above object, the invention according to claim 1 provides the following: when an element on the front side and an element on the back side of a figure created in a two-dimensional CAD system overlap, This hidden line processing method changes the elements on the back side of this overlapping part to hidden line representation, and includes the step of extracting the element data on the front side, and the step of extracting the element data on the outermost side to form a closed area. This step consists of a step of extracting data of an element to be the back side, and a step of performing hidden line processing on the back side element when the back side area exists in the closed area defined above.

The invention according to claim 2 provides the above method, in which the outermost element data is extracted by vector calculation around a predetermined direction from a predetermined point of the front side element, and the closed 89R area is determined by sorting the outermost elements so as to be continuous. This is what I did.

The invention according to claim 3 changes, when an element on the front side and an element on the back side of a figure created in a two-dimensional CAD system overlap, the element on the back side of the overlapping part to a hidden line representation. A hidden line processing device, comprising means for extracting element data for the front side, means for extracting element data for the outermost part of the element data to form a closed area, means for extracting element data for the back side, and the above-mentioned When a back side area exists in the defined closed area, it consists of a means for hidden line processing of the back side element. [Operation] According to the above method or device, element data for the front side is extracted. At the same time, the outermost element data is extracted to form a closed area. Further, data of an element serving as a back side is extracted, and when a back side area exists in the closed area defined above, the back side element is changed to a hidden line.

[Embodiment 1] Hereinafter, a hidden line processing method and apparatus for a drawing creation CAD system of the present invention will be explained with reference to the drawings.

FIG. 1 shows the block configuration of this CAD system. This system consists of a main memory and a calculation and control unit.
The system consists of a ROM 2 that stores PUI, CaC2''ograms, etc., and a RAM 3 that serves as a work area for graphic processing, and various input/output devices connected via an interface 4.The input/output devices include architectural drawings, etc. A hard disk 5 that stores various graphic data such as, a keyboard 6 and a mouse 7 that input various drawing processing commands, a display 8 (display device) that displays processed graphics, and a plotter 9 that plots the graphics on paper. etc. are provided.

The operation keys consisting of the system body, keyboard 6, and mouse 7 are a means for extracting element data for the front side, a means for extracting the outermost element data to form a closed area, and a means for extracting element data for the back side. The system body performs the function of means for hidden line processing of the back side element when the back side area exists in the closed area.

The operating procedure of hidden line processing by this apparatus will be explained with reference to FIGS. 2, 3(a) and 3(b), FIG. 4, and FIG. 5. In the operation of the hidden line processing application, as shown in Figure 2, first, the elements (components) on the front side are
(#1).

Regarding the front and back elements, attributes are stored in advance in the database of the CAD system for each group or partial part. The element instructions are as shown in Figure 3(a).
The search routine is executed by positioning the cursor using the mouse 7 on a part of the line of the front part of the drawing displayed on the display 8 and clicking it. Next, designate the elements on the back side in the same way (#2). Then, hidden line processing is executed (#3). As a result, the lines of the back side elements are deleted as shown in FIG. 3(b).

The processing in the system according to the above operation is as shown in FIG. That is, the elements on the front side are extracted (#11), and the elements on the outermost side are sorted (#12). This will sort the closed area (#1
3) The shaded area in FIG. 5(a) corresponds to a closed area on a two-dimensional plane. Next, the line of the back side element is divided at the closed area (#14). The screen state at this time is 5th
As shown in Figure (b), the back side element ■ is created by the closed figure ■.
line is divided. Then, for inside the closed area,
For example, when processing counterclockwise, elements on the left side of each intersection are deleted (#15).

The hidden line processing is completed by performing the above processing until there are no more back side elements (#16).

A method of creating a closed area by sorting the outermost elements will be described below with reference to FIGS. 6, 7, and 8. Now, if we take out the figure element on the front side as shown in Figure 6, we will set the search start element for extracting the outermost element as the minimum value of the (x, y) coordinates in the element group of this figure. Let the element ■ have , and start searching clockwise. The second element has the end point of the element (2) as an end point or an intersection point, but since only the element (2) is located here, the element (2) is designated as the second element. Next, in order to determine the third element, select the element that has the end point of element ■ as an end point or intersection point.
It is decomposed into vectors a1 to a5 as shown in the figure. Then, in order to determine whether each element is on the left or right side with respect to element (2), xai-m is calculated, and if this is negative, it is determined that it is on the right side.

However, ■■ is the vector quantity of element ■, and m is the three-dimensional value (0,
0,1).

Next, a, which is determined to be the right-hand element, is a.

To determine which is more to the right, a
XB, · m 11 t2 is determined, and if this is negative, it is determined that a, 1 is on the right side.

al can be extracted by the above calculation. below,
Similar processing is performed to determine the rightmost element. Next, the elements extracted as described above are sorted so that the starting and ending points are continuous to create a closed area. Thereafter, the backside element may be divided into closed regions, and the elements within the closed regions may be taken out and deleted. At this time, the left side element within the closed area is deleted with respect to the intersection of the line of the back side element and the line of the outermost element forming the closed area. If there is no intersection, extend the line of the back side element in both directions from the start and end points, find the intersection, and follow the above process. If the intersection cannot be found, it may be determined that it is outside the closed area.

Note that the present invention is not limited to the method and device configuration of the above-described embodiments, and, for example, the method of removing the back side element existing in the closed area, etc. can be executed in various modified forms.

Effect of one invention] As described above, according to the invention according to claim 1 or 3, 3
Using two-dimensional data without dimensional data, we create a closed g-area using the outermost elements of the front side elements, and change the back side elements existing in the closed area to hidden line representations, so each element on the front and back sides can be expressed as Hidden line processing can be easily performed by simply specifying the operation.

Further, according to the invention as set forth in claim 2, in addition to the above-mentioned effects, it is possible to create a closed region by relatively simple calculations, thereby speeding up the processing.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a CAD system implementing the hidden line processing method in a two-dimensional CAD system of the present invention, FIG. 2 is a flowchart showing the operating procedure for hidden line processing, and FIG.
Figures (a) and (b) are diagrams showing the changes in the figure at that time.
The figure is a flowchart showing the processing procedure of the same layer line processing.
Figures <a) and (b) are diagrams showing the concept of the same processing method, Fig. 6,
Figures 7 and 8 are diagrams for explaining the method of extracting the outermost element, Figure 9 is a flowchart showing the conventional hidden line processing method, and Figures 10 (a) and (b) are diagrams for explaining the method for extracting the outermost element. 11 and 12 are diagrams showing the concept of the conventional hidden line processing method, and FIG. 13 is a diagram showing the conventional operation procedure. 1...CPU, 6...Keyboard, 7...Mouse, 8...Display. Applicant: Daikin Industries, Ltd. Figure 3 (a) Figure (a) Figure (a) Figure ■ Figure 13

Claims (3)

[Claims] (1) When the front and back elements of a figure created in a two-dimensional CAD system overlap, a hidden line processing method that changes the back side of the overlapping part to a hidden line representation. , a step of extracting the element data for the front side, a step of extracting the outermost element data to form a closed area, a step of extracting the data of the elements for the back side, and the step of extracting the element data for the back side. 1. A hidden line processing method in a two-dimensional CAD system, comprising the step of, when a back side area exists in a closed area, performing hidden line removal on a back side element. (2) A claim characterized in that the outermost element data is extracted by vector calculation around a predetermined direction from a predetermined point on the front side element, and the closed area is created by sorting the outermost elements so as to be continuous. Hidden line processing method in a two-dimensional CAD system according to 1. (3) When the front side element and the back side element of a figure created in a two-dimensional CAD system overlap, a hidden line processing device that changes the element on the back side of the overlapping part to a hidden line representation. means for extracting element data for the front side, a means for extracting element data for the outermost part of the element data to form a closed area, a means for extracting element data for the back side, and a closure created by the above. 1. A hidden line processing device for a two-dimensional CAD system, comprising means for performing hidden line processing on a back side element when a back side area exists in the area.