JP2005084740A - Cad device, offset line drawing method, and cad program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To draw a parallel line or widened line of a clothoid curve without using any approximation. <P>SOLUTION: A user designates the clothoid curve that is a reference, and also designates an offset value and the side of drawing the offset line (parallel line or widened line) to the clothoid curve. The CAD device divides the designated clothoid curve at a predetermined dividing pitch p to specify division points. The CAD device determines, for each division point, an offset point which is located on the side designated by the user in a direction vertical to the tangent at the division point concerned and has a distance from the division point equal to the offset value. The offset points are complemented with a straight line to draw the offset line of the clothoid curve. When the offset values differ at one end side and the other end side of the clothoid curve, the difference in offset value between the one end side and the other end side is proportionally divided to the offset value at each division point according to the distance from the one end of the clothoid curve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a CAD apparatus and the like, for example, relates to an apparatus for drawing a relaxation curve in road alignment planning.

Along with the rapid development of computers in recent years, the creation of design drawings that have been performed manually using a drafter or the like has been performed using a CAD (Computer Aided Design) apparatus.
The CAD device is a design support device using a computer, and can perform drawing on a display using an input device such as a mouse, a tablet, or a keyboard.

A coordinate system is set on the display, and the user arranges various drawing elements such as points, straight lines, and circles on the coordinate system and creates a design drawing.
CAD offers a variety of products from general-purpose products to those specialized in specific fields such as architectural, mechanical design, and electronic circuit design. Select and use.
Of these fields, CAD is used to design roads in road alignment planning (civil engineering).

The road design is mainly composed of straight parts and curved parts, but usually there is a relaxation section where the radius of curvature gradually changes from the straight line in the section from the straight part to the arc part of the curve. It is done.
The shape of the relaxation section is designed along a predetermined relaxation curve. A typical example of this relaxation curve is a clothoid curve.
If the relaxation zone is a clothoid curve shape, the driver can gradually tilt the steering wheel when entering the curve and gradually return the steering wheel when exiting the curve. Can be increased.

When designing a curve portion of a road using a CAD device, the center line is first drawn with a clothoid curve. Then, the clothoid curve is offset to draw parallel lines and widening lines (described later) to design road shoulders and sidewalks.
In addition, when designing a curve portion in consideration of the difference between the inner wheels of the vehicle, the widening is set in the lane inside the curve.

By the way, although a clothoid curve can be expressed mathematically, parallel lines and widening lines of the clothoid curve cannot be expressed mathematically.
Therefore, conventionally, these parallel lines have been approximated using pseudo arcs or Bezier curves.
As described above, as a technique for approximating a curve parallel to a clothoid curve by a Bezier curve, there is a “CAD system” of the following document.

JP 2001-184514 A

However, in the conventional CAD apparatus, since these parallel lines and widening lines are approximate curves, a deviation from the original shape was observed when measured on a paper medium.
In road alignment plans, design changes are frequently made due to land acquisition progress and other reasons, but if the position and shape of the centerline are changed due to design changes, an approximate curve must be drawn from the beginning again. In other words, it has been difficult to secondarily use the already drawn approximate curve.
Therefore, it has been a heavy burden on the user to draw an approximate curve from the beginning every time the design is changed.

  Therefore, an object of the present invention is to provide a CAD apparatus and the like that can draw parallel lines and widening lines of clothoid curves without using approximation.

In order to achieve the above object, according to the present invention, in the invention described in claim 1, clothoid curve designating means for designating a clothoid curve in a design drawing composed of electronic information, and a plurality of clothoid curves on the designated clothoid curve line are provided. A point specifying unit for specifying the point, an offset value acquiring unit for acquiring an offset value, a predetermined side of the clothoid curve, and perpendicular to a tangent at the point of the clothoid curve from each of the specified points An offset point specifying means for specifying an offset point at a distance of the acquired offset value in a direction, and a presenting means for complementing a space between the acquired offset points with a straight line or a curve and presenting it together with the clothoid curve A CAD apparatus characterized by comprising: is provided.
According to a second aspect of the present invention, when the offset value acquired by the offset value acquiring unit is different between one end and the other end of the clothoid curve, the offset point specifying unit is a distance from the one end of the clothoid curve. The CAD device according to claim 1, wherein a difference between the offset values of the one end and the other end is distributed to the offset value of the specified point at a predetermined ratio according to the above.
The invention according to claim 3 provides the CAD device according to claim 1 or 2, wherein the point specifying means specifies the point at predetermined intervals along the clothoid curve. To do.
In the invention according to claim 4, the presenting means identifies points at predetermined intervals along the clothoid curve, and presents the clothoid curve by complementing the identified points with a straight line or a curve, 4. The CAD apparatus according to claim 3, wherein the predetermined interval for specifying points on the clothoid curve by the offset point specifying means is equal to the predetermined interval for specifying points on the clothoid curve by the presenting means. To do.
In a fifth aspect of the present invention, in a CAD device comprising a clothoid curve specifying means, a point specifying means, an offset value acquiring means, and a presenting means, and configured by a computer, the clothoid curve specifying means A clothoid curve designating step of designating a clothoid curve in a design drawing composed of information, a point specifying step of specifying a plurality of points on the line of the specified clothoid curve by the point specifying means, and the offset value acquiring means The offset value acquisition step of acquiring an offset value and the offset value acquisition means are on a predetermined side of the clothoid curve and from each of the identified points in a direction perpendicular to a tangent at the point of the clothoid curve The offset point that is located in the distance of the acquired offset value is specified. An offset line comprising: a set point specifying step; and a presentation step of presenting together with the clothoid curve by complementing a space between the acquired offset points with a straight line or a curve by the presenting means Provide a drawing method.
In the invention according to claim 6, a clothoid curve designating function for designating a clothoid curve in a design drawing composed of electronic information, a point identifying function for identifying a plurality of points on a line of the designated clothoid curve, and an offset value An offset value acquisition function for acquiring the distance between the acquired offset value and a predetermined side of the clothoid curve in a direction perpendicular to a tangent at the point of the clothoid curve from each of the specified points There is provided a CAD program for realizing an offset point specifying function for specifying an offset point and a presentation function for complementing a space between the obtained offset points with a straight line or a curve and presenting it together with the clothoid curve.

  The present invention can draw a parallel line or a widening line of a clothoid curve without using approximation.

(Outline of the embodiment)
First, the user specifies a reference clothoid curve, and also specifies an offset value and a side on which an offset line (parallel line or widening line) is drawn with respect to the clothoid curve.
On the other hand, the CAD device first divides a specified clothoid curve with a predetermined division pitch p and specifies a division point.

Then, the CAD device obtains, for each division point, an offset point that is on the side specified by the user in a direction perpendicular to the tangent at the division point and whose distance from the division point is an offset value.
Then, the offset line of the clothoid curve is drawn by complementing the adjacent offset points with a straight line.

  If the offset value differs between the one end side and the other end side of the clothoid curve, the difference between the offset values on the one end side and the other end side is converted into the offset value at each dividing point according to the distance from the one end of the clothoid curve. Proportional distribution.

(Details of the embodiment)
The CAD device is a computer device that supports design, and includes a display device such as a display, a printing device such as a laser printer and a plotter, and an input device such as a keyboard, a mouse, and a tablet.
The user creates a design drawing by arranging drawing elements such as a point marker, a line segment, a circle, and a dimension line on the virtual design drawing displayed on the display device using the input device. .
The created design drawing is stored in the storage device as electronic data, and is also output (printed) on a paper medium or the like by the printing device.

Various types of CAD devices are provided depending on the design object, such as civil engineering design, architectural design, mechanical design, and so on.
In the field of road alignment planning (civil engineering), design by CAD is actively performed, and roads are designed by assembling drawing elements having various geometric shapes.

The curve portion of the road is generally designed so that the shape of the center line of the curve is a clothoid curve.
Here, the clothoid curve will be described with reference to FIG.
The clothoid curve 3 can be represented by the following equation (1), where R is the curvature of a point of length L along the curve from the origin O.

R × L = A ² (1)

The radius R at the starting point is ∞. A is defined in a squared form to match the left side with the dimension.
As is clear from Equation (1), the curvature R decreases as the distance L along the clothoid curve from the starting point increases.
Therefore, when the clothoid curve section 3 is formed from the straight section 1 (R = ∞) to the arc section 2 (R = R1), the curvature of the curve portion is gradually changed from R = ∞ to R = R1. Can do.

FIG. 2 is a diagram illustrating an example of the curve portion 6 drawn using the CAD apparatus according to the present embodiment.
Note that the drawing refers to presenting a drawing target to the user by displaying on a display or printing on a paper medium.
The calculation method for drawing the curve portion and the hardware configuration of the CAD apparatus will be described in detail later.

In the curve portion 6, the straight line section on the start point side and the straight line section on the end point side are smoothly connected by the clothoid curve section and the arc section.
Note that the start point side and the end point side are defined for the sake of design, and are not related to the ups and downs of the road.

In designing the curved portion 6, first, center lines (straight line 7a, clothoid curve 7b, arc 7c, clothoid curve 7d, straight line 7e) are set based on the survey results and the like.
The curvature R of the clothoid curve 7b at the end point on the straight line 7a is ∞, and the curvature R at the end point on the arc 7c side is equal to the curvature of the arc 7c.
The same applies to the clothoid curve 7d.

The line outside the curve portion 6 is at a position that is separated from the center line by a predetermined offset value (design value).
That is, the straight line 8a, the parallel line 8b, the circular arc 8c, the parallel line 8d, and the straight line 8e are respectively centered by a predetermined offset value (Ws) from the straight line 7a, the clothoid curve 7b, the arc 7c, the clothoid curve 7d, and the straight line 7e. It is located outside.
In general, the lane portion outside the curve portion is not widened in consideration of the inner wheel difference, and the offset values from the start point side to the end point side are equal.
It is also possible to design the outer lane so as to install a widening.

The inner line of the curve portion 6 is located at a predetermined offset value from the center line, but the offset value (We) of the arc 9c portion is set to the offset value (Ws) of the straight line portion in consideration of the inner ring difference. And larger).
That is, the straight lines 9a and 9e and the straight lines 7a and 7e are parallel lines separated by the offset value Ws, respectively, and the arc 9c and the arc 7c are parallel lines separated by the offset value We. And We> Ws.

The offset values of the clothoid curve 7b and the widening line 9b are Ws on the straight line side, We on the arc side, and are set so that the offset value gradually increases from the straight line side to the arc side.
Thus, when the offset value differs between the start point and the end point, the offset amount is proportionally distributed according to the distance on the center line in the clothoid section.
Therefore, the width of the widening line 9b gradually increases from the straight line side to the arc side. A curve in which the offset value is changed in consideration of the inner ring difference is called a widening line.
Hereinafter, when the parallel lines and the widening lines are not distinguished, these are simply referred to as offset lines.

  Next, the CAD apparatus according to the present embodiment (1) draws a parallel line of the clothoid curve (parallel lines 8b and 8d), and (2) draws a widening line (widening lines 9b and 9d) of the clothoid curve. How to do will be described.

(1) A method of drawing parallel lines of clothoid curves.
A method in which the CAD apparatus of the present embodiment draws parallel lines 8b will be described with reference to FIG.
First, as shown in FIG. 3A, the CAD device divides the clothoid curve 7b at an equal pitch (referred to as a division pitch p), and obtains coordinate values of the division points 10, 10,.

Next, as shown in FIG. 3 (b), from each division point, there is a direction perpendicular to the clothoid curve 7b (more specifically, a direction perpendicular to the parallel line at the division point of the clothoid curve 7b). The coordinate values of the offset points 11, 11,... At the position of the offset value Ws from the point are obtained.
These offset points 11, 11,... Are points on a curve parallel to the clothoid curve 7b.
Next, as shown in FIG. 3C, a parallel line 8b is obtained by complementing the points between the adjacent offset points 11, 11,.

In general, when a CAD apparatus displays a curve on a display or prints it on a paper medium, the CAD apparatus divides the curve at a predetermined pitch and draws the divided points by complementing them with straight lines.
Here, the finer the pitch, the closer to the original shape of the curve to be drawn, and the rougher the pitch, the different the shape from the original curve.

On the other hand, the finer the pitch, the more calculation processing, the lower the performance of the CAD device, and the rougher the pitch, the faster the calculation processing.
Therefore, how much the pitch is set is an important factor.

In this embodiment, the curve drawing pitch is set between 0.1 [mm] and 0.5 [mm] in consideration of the calculation load applied to the CAD device and the drawing accuracy.
The division pitch p for dividing the clothoid curve 7b is also set equal to the curve drawing pitch.
Therefore, it is possible to draw the parallel line 8b as accurately as the reference clothoid curve 7b.
The parallel line 8d is obtained in the same manner.

Even when the drawing scale of the design object is changed by changing the scale of the drawing, the curve drawing pitch and the division pitch p do not change.
Further, in the present embodiment, the curve drawing pitch and the division pitch p are set equal, but the present invention is not limited to this, and other settings may be used.

For example, since the parallel lines are located outside the clothoid curve, the pitch of the offset points is larger than the division pitch. Therefore, when the offset point is complemented with a straight line, the drawing may become rough.
Therefore, in order to prevent this, the division pitch p can be set to a value smaller than the curve drawing pitch.

In the above description, the division pitch p is constant. However, the present invention is not limited to this. For example, the division pitch p may be changed according to the position on the clothoid curve.
When the offset curve is drawn outside the clothoid curve, the interval between the offset points corresponding to the portion where the curvature of the clothoid curve is small becomes larger than the portion where the curvature is large. That is, the offset line can be drawn more accurately.

Next, a procedure for generating a clothoid parallel line will be described with reference to the flowchart of FIG.
The following processing is performed by a CPU (Central Processing Unit) arranged in the CAD device according to a predetermined program.

First, the CAD device specifies a clothoid curve serving as a reference for parallel lines (step 5).
This is performed, for example, when the user designates a clothoid curve displayed on the display by operating the mouse or the like. As described above, the CAD apparatus includes a designation unit.

Next, the CAD device divides the clothoid curve specified in step 5 at a predetermined pitch p, and calculates the coordinate value of the dividing point (step 10). This function is based on the point specifying means provided in the CAD device.
The pitch p is set equal to the drawing pitch of the curve and is stored in advance in the CAD device.

Next, the CAD device draws parallel lines of the clothoid curve, and is an offset point that is in a direction perpendicular to the clothoid curve (its tangent) from each division point and whose distance from the division point is W (offset value). Is calculated (step 15). As described above, the CAD apparatus includes an offset point specifying unit.
The designation of the drawing side of the parallel lines and the designation of the offset value W are performed by the user, for example, when selecting a reference clothoid curve.

Next, the CAD device complements the interval between the offset points obtained in step 15 with a straight line, and draws a parallel line of the clothoid curve (step 20). As described above, the CAD apparatus includes a presentation unit that draws and presents an offset line.
In the present embodiment, the offset points are complemented by straight lines, but may be complemented by other curves such as arcs or Bezier curves.

Next, data held by the CAD device will be described.
In order to draw a clothoid curve, the CAD device holds data such as clothoid parameters (start point coordinates, start point direction, A, separate left and right) for each clothoid curve.
Here, the “starting point direction” is a direction in which a clothoid curve starts to be drawn from the starting point, and “A” is A in Expression (1).

In order to draw a parallel line of a clothoid curve, the CAD device holds an offset value W in addition to these clothoid parameters.
If the clothoid parameter and the offset value W are stored, the CAD apparatus can draw parallel lines according to the procedure of FIG.
Therefore, even when the shape or position of the clothoid curve is changed due to a road plan change or the like, the CAD device can draw the parallel lines of the changed clothoid curve simply by changing the corresponding part of the clothoid parameter.

That is, in the CAD apparatus, the information holding method is an abstract method of center line information and offset information, and the geometric information of the offset line itself is not held as it is.
Therefore, when updating the offset line, it is only necessary to change the information of the center line. In road design work, the design change of the center line often occurs, which is useful.

(2) A method of drawing a widening line on the basis of a clothoid curve.
With reference to FIG. 5, description will be given of a method in which the CAD apparatus of the present embodiment draws the widening line 9b.
Even when the offset values on the start point side and the end point side are different, the clothoid curve 7b is divided at the division pitch p in the same manner as in FIG. Then, the coordinate value of the offset point that is separated by a predetermined offset amount in the direction perpendicular to the clothoid curve from each division point is obtained.
At this time, the offset value Wn of the nth offset point from the start point side is defined by the following equation (2).

  Wn = Ws + Ln (We−Ws) / L (2)

However, L is the full length of the clothoid curve 7b, and Ln is the distance along the clothoid curve 7b from the start point side to the nth division point.
If defined in this way, the offset value Wn is a value obtained by proportionally distributing the difference between the start point side offset value Ws and the end point side offset value We by the distance on the clothoid curve.

  When the offset points are obtained in this way and are connected by a straight line, the offset value on the start point side is Ws and the offset value on the end point side is We as shown in FIG. 5, and from the start point side to the end point side. It is possible to draw the widening line 9b whose offset value increases in proportion to the distance from the starting point side.

The widening line 9d can be similarly drawn.
However, in the case of the widening line 9d, the width becomes narrower from the start point side to the end point side, so Wn may be defined by the following equation (3).

  Wn = We−Ln (We−Ws) / L (3)

  In the present embodiment, the offset value Wn is proportionally distributed. However, the present invention is not limited to this, and the offset value Wn can be defined using other methods.

  Next, a procedure for drawing the widening line when the offset value is different between the start point and the end point will be described using the flowchart of FIG. However, the offset value on the start point side is smaller than the offset value on the end point side.

First, the CAD device specifies a clothoid curve serving as a curve reference (step 50). This is specified when the user designates it with a mouse operation or the like.
Further, the user designates the offset value Ws on the start point side, the offset value We on the end point side, and the drawing side of the curve, and the CAD device stores them.

Next, the CAD device divides the clothoid curve identified in step 50 at a predetermined division pitch p, and calculates the coordinate value of the division point (step 55).
Here, the CAD device counts and stores the total number N of division points.

Next, the CAD device sets a counter n to 0 (step 60).
Then, the CAD device calculates Wn for the nth division point using equation (2) (step 65).
The dividing points are 0th, 1st,..., N−1th in order from the start point side.

From the nth division point, the coordinate value of the offset point located at the distance Wn in the vertical direction from the clothoid curve (its tangent) is calculated on the side designated by the user (step 70).
The CAD device stores the calculated coordinate value of the offset point.
Next, the CAD device sets n = n + 1 and increments n by 1 (step 75).

Next, the CAD device determines whether n is smaller than N (step 80).
If n is smaller than N (step 80; N), there is a division point for which an offset point has not yet been obtained, so the process returns to step 65 to obtain an offset point for the next division point.

  When n is greater than or equal to N (more specifically, when n satisfies n = N), since the offset points have been obtained for all the dividing points, the CAD apparatus determines the interval between adjacent offset points. Are connected by a straight line to draw a widening line (step 85).

According to the above procedure, when the offset value Ws on the start point side and the offset value We on the end point side are different, the difference between We and Ws is distributed in a predetermined ratio to the clothoid curve based on the offset value (here, proportional distribution) ) Can be drawn.
If the offset value on the start point side is larger than the offset value on the end point side, equation (3) may be used in step 65.

When the offset values on the start point side and the end point side are different, the CAD device uses the clothoid parameters of the reference clothoid curve (start point coordinates, start point direction, A, separate from left and right) and the start point side offset value Ws, And the offset value We on the end point side.
If these data are held, the widening line can be drawn from the formula (2) or the formula (3).

Next, the hardware configuration of the CAD apparatus according to the present embodiment will be described with reference to FIG.
In the CAD device, an input unit 82, an output unit 83, a communication control unit 84, a storage unit 85, a storage medium driving unit 88, an input / output I / F (interface) 89, and the like are connected to the control unit 76 via a bus line 77. Configured.

The control unit 76 performs various types of information processing such as various calculations, data management, and screen display when the user performs the drafting work, and controls the printing apparatus and the input apparatus.
The control unit 76 includes a CPU 78, a ROM (Read Only Memory) 80, a RAM (Random Access Memory) 81, and the like.

The CPU 78 performs information processing and control of the CAD device according to a predetermined program. The CPU 78 has a storage unit called a register. A program is read into the register from the ROM 80, the RAM 81, and the like, and various functions of the control unit 76 are exhibited by operating according to the program.
As described above, the CPU 78 can draw a parallel line of the clothoid curve based on the clothoid curve and a curve having different offset values on the start point side and the end point side.

  The ROM 80 is a read-only memory that stores various programs, data, parameters, and the like for the CPU 78 to perform various calculations and controls. The CPU 78 can read programs, data, parameters, and the like from the ROM 80, but does not rewrite or delete them.

The RAM 81 is a random access memory used as a working memory for the CPU 78. The CPU 78 can write and erase programs and data in the RAM 81.
In the present embodiment, an area for drawing the clothoid curve offset line can be secured in the RAM 81.

The input unit 82 includes an input device such as a keyboard, a mouse, or a tablet.
The input unit 82 is a device for inputting various data such as characters and numbers to the CAD device, and can designate a side on which an offset line of a clothoid curve is drawn and can input an offset value.
The keyboard includes keys for inputting kana and English characters, numeric keys for inputting numbers, various function keys, cursor keys, and other keys.

A mouse and a tablet are pointing devices. When operating a CAD apparatus using a GUI (Graphical User Interface) or the like, predetermined information can be input by clicking a button or icon displayed on the display apparatus with a mouse.
For example, it can be selected by clicking on a clothoid curve serving as a reference for drawing an offset line.

The output unit 83 includes, for example, a display device, a printing device, and the like, and is used when outputting a verification result verified by the CAD device.
The display device is a device for presenting information on a screen, for example, a CRT (Cathode Ray Tube) display, a liquid crystal display, a plasma display, or the like.
The display device can display a design drawing being created or after creation, and the user performs a design operation on the design drawing displayed on the display device.
The printing apparatus includes, for example, various printer apparatuses such as an inkjet printer, a laser printer, a thermal transfer printer, and a dot printer in addition to a plotter.

The communication control unit 84 is a device for connecting the CAD device to a network such as the Internet, and includes a modem, a terminal adapter, and other connection devices.
The CAD device can access an external terminal or server using the communication control unit 84.
The drawing data can be transmitted / received to / from another computer via the communication control unit 84.
Also, the created drawing can be delivered electronically via the communication control unit 84.

  The storage unit 85 includes a readable / writable storage medium and a drive device for reading / writing programs and data from / to the storage medium. A hard disk is mainly used as the storage medium, but other storage media that can be read and written, such as a magneto-optical disk, a magnetic disk, and a semiconductor memory, can also be used.

The storage unit 85 includes a program storage unit 86, a data storage unit 87, and the like, which store programs and data, respectively.
The program storage unit 86 includes a CAD program for causing the CAD device to exhibit a design drawing creation function, an OS (Operating System) that is a basic program for operating the CAD device such as memory management and input / output management, and communication. A communication program for controlling the control unit 84 and other various programs are stored.
The data storage unit 87 stores CAD data designed or being designed by the user.

  The storage medium driving unit 88 is a driving device for driving a removable storage medium to read / write data. Examples of the removable storage medium include a magneto-optical disk, a magnetic disk, a magnetic tape, a semiconductor memory, a paper tape punched with data, and a CD-ROM. Note that CD-ROMs and paper tapes can only be read.

  The input / output I / F 89 is configured by, for example, a serial interface or another standard interface. By connecting an external device corresponding to the interface to the input / output I / F 89, the function of the CAD device can be expanded.

According to the present embodiment described above, the following effects can be obtained.
(1) It is possible to draw an offset line of a clothoid curve without using approximation. Therefore, an original curve can be drawn.
(2) Even when the offset values on the start point side and the end point side are different, an offset line can be drawn by proportionally allocating the offset value. Therefore, an original curve can be drawn even when the road is designed in consideration of the inner ring difference.
(3) In order to draw the offset line of the clothoid curve, in addition to the data for drawing the clothoid curve (road center line), the start point side offset value and the end point side offset value (when the start point side and the end point side are the same offset value) Need only hold its offset value). Therefore, the offset line for the changed clothoid curve can be drawn only by changing the data regarding the center line (clothoid curve).

  Moreover, although the case where a clothoid curve is offset by CAD for civil engineering design as an example was demonstrated above, it is not limited to this, It can apply widely also to CAD of the other field | area which offsets a clothoid curve.

It is a figure for demonstrating a clothoid curve. It is the figure which showed an example of the drawing of the curve location by the CAD apparatus of this Embodiment. It is a figure for demonstrating the method of drawing the parallel line of a clothoid curve. It is a flowchart for demonstrating the procedure which produces | generates the parallel line of a clothoid curve. It is a figure for demonstrating the method of drawing the widening line of a clothoid curve. It is a flowchart for demonstrating the procedure which draws the widening line of a clothoid curve. It is the figure which showed an example of the hardware constitutions of the CAD apparatus of this Embodiment.

Explanation of symbols

1 straight section 2 arc section 3 clothoid curve section 7a straight line 7b clothoid curve 7c arc 7d clothoid curve 7e straight line 8a straight line 8b parallel line 8c circular arc 8d parallel line 8e straight line 9a straight line 9b widening line 9c circular line 9d widening line 9d

Claims (6)

Clothoid curve designating means for designating a clothoid curve in a design drawing composed of electronic information;
Point specifying means for specifying a plurality of points on the specified clothoid curve line;
An offset value acquisition means for acquiring an offset value;
Offset point specifying means for specifying an offset point at a distance of the acquired offset value in a direction perpendicular to a tangent at the point of the clothoid curve from each of the specified points on the predetermined side of the clothoid curve When,
The presenting means for complementing the acquired offset points with a straight line or a curve and presenting it together with the clothoid curve,
A CAD apparatus comprising: When the offset value acquired by the offset value acquisition unit is different at one end and the other end of the clothoid curve,
The offset point specifying means includes
The difference between the offset values of the one end and the other end is distributed to the offset value of the specified point at a predetermined ratio according to the distance from the one end of the clothoid curve. CAD equipment.   The CAD device according to claim 1, wherein the point specifying unit specifies the point at predetermined intervals along the clothoid curve. The presenting means identifies points at predetermined intervals along the clothoid curve, and presents the clothoid curve by complementing the identified points with a straight line or a curve,
4. The CAD apparatus according to claim 3, wherein the predetermined interval at which the offset point specifying means specifies points on the clothoid curve is equal to the predetermined interval at which the presentation means specifies points on the clothoid curve. In a CAD device comprising a clothoid curve specifying means, a point specifying means, an offset value acquiring means, and a presenting means, and configured by a computer,
A clothoid curve specifying step of specifying a clothoid curve in a design drawing composed of electronic information by the clothoid curve specifying means;
A point specifying step of specifying a plurality of points on the line of the specified clothoid curve by the point specifying means;
An offset value acquisition step of acquiring an offset value by the offset value acquisition means;
An offset point that is on the predetermined side of the clothoid curve by the offset value acquisition means and is at a distance of the acquired offset value from each of the identified points in a direction perpendicular to a tangent at the point of the clothoid curve Offset point identifying step for identifying
The presenting means complements the obtained offset points with a straight line or a curve, and presents it together with the clothoid curve,
An offset line drawing method comprising: A clothoid curve designation function that designates a clothoid curve in a design drawing composed of electronic information,
A point specifying function for specifying a plurality of points on the specified clothoid curve line;
An offset value acquisition function for acquiring an offset value;
An offset point specifying function that specifies an offset point that is on the predetermined side of the clothoid curve and that is at a distance of the acquired offset value in a direction perpendicular to a tangent at the point of the clothoid curve from each of the specified points When,
A presentation function that complements the acquired offset points with a straight line or a curve, and presents it together with the clothoid curve,
CAD program that realizes the above on a computer.

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