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Application example of CAD geometric calculator

geometric calculator is a very useful tool provided by AutoCAD R12. Like ordinary calculators, geometric calculators can complete the operations of +, -, * and/and trigonometric functions. This enables users to use the computer to perform arithmetic operations without interrupting the command in the process of drawing with AutoCAD, and AutoCAD directly uses the results of the operations as the parameters of the command. However, it is important that, unlike ordinary calculators, AutoCAD geometric calculators can perform geometric operations. It can perform addition and subtraction operations between coordinate points, capture coordinate points on the screen with AutoCAD osnap mode, and automatically calculate geometric coordinate points. For example, calculate the intersection of two intersecting lines, and calculate the bisector points on the line. In addition, AutoCAD geometric calculator also has the function of calculating vectors and normals. Of course, AutoCAD geometric calculator has other functions, which are not listed here

in AutoCAD drawing, it is often necessary to determine some points that cannot be directly given coordinates. For example, the midpoint between any two points; Center of the a circle tangent to a straight line in any direction; And any bisection point on the straight line. This is what we usually call the positioning problem of CAD drawing. In fact, in many computer drawing occasions, whether the positioning is convenient and accurate often directly affects the efficiency and speed of drawing. Therefore, we should make full use of the geometric operation function of AutoCAD geometric calculator to achieve rapid positioning in AutoCAD drawing

at the command prompt command: type cal or activate the auxiliary menu item of the drop-down menu. Pick the geometric calculation menu item to start the AutoCAD geometric calculator. Cal command is also a transparent command, which can start the geometric calculator at any time under other commands. In addition, Cal commands can be used in AutoLISP programs

the following are several examples of quick positioning that are often encountered in AutoCAD drawing by using the geometric operation function of AutoCAD geometric calculator

1. Determine the midpoint between the two entities

there is no need to draw an auxiliary line between the two entities first, and then use osnap's mid mode to get the midpoint. For example, draw a line from the center between the center of a circle and the endpoint of a line. The operation process is as follows:

command: Line

from point: cal (start the geometric calculator)

expression: (cen+end)/2 (enter the expression, where the calculator takes the cen and end modes of osnap as the temporary storage unit of point coordinates)

select entity for Cen snap uses the cursor to capture the center of the circle)

select entity for end snap uses the cursor to capture the endpoint of the line)

to point:

other target capture modules, but until the past 35 years, formulas such as int, INS, Tan, etc. can be used in geometric calculation expressions. If the expression (cen+end)/2 is replaced by the expression (cur + cur)/2, the osnap mode can be set to capture the required points when the computer requires the input of points

2. Determine a straight line to produce any bisection point on the PVC product that meets the demand and the point with the fixed length with the end of the straight line

this operation can be completed by using the PLT and PLD functions provided by the geometric calculator. Suppose there is a straight line with endpoints A and B on the screen, and the point on which the division line AB is 1:2 should be obtained. Take drawing a straight line as an example, The operation process is as follows:

command: Line

from point: cal

expression: PLT (end, end, 1/3)

select entity for end snap capture endpoint B with cursor to get a point 1/3 of the line segment from point a)

to point:

if you want to get a point 5 from endpoint a on a straight line, Use the function PLD (end, end, 5) instead of PLT (end, end, 1/3) in the above operation

3. use relative coordinates to determine points

in drawing, it is often necessary to draw another line relative to one line, The following is the operation process:

command: Line

from point: cal

expression: end+[2,3] (add points and points)

select entity for end snap after capturing the endpoint of a datum line, you can obtain the point with relative displacement (2, 3) from the endpoint)

to point:

this function is similar to the from target capture mode provided in AutoCAD R13

4. make a circle tangent to a diagonal line and a tangent to a circle through a point on the circle

using AutoCAD orthogonal mode, you can easily draw a circle tangent to a vertical line or a horizontal line. To draw a circle tangent to the slash, you need to accurately determine the center of the circle. The operation process is as follows:

command: circle

3p/2p/ttr/: cal

expression: cur+3*nee (cur means picking a point on the screen with the cursor, nee function Shanghai) is used to calculate the normal of the point vector at both ends, 3 is the radius of the circle)

enter a point:nea (use the cursor to capture a point on the line as the tangent point of the circle and the line)

to select one endpoint for nee use the cursor to capture one endpoint of the line)

select another endpoint for nee use the cursor to capture another endpoint on the line)

diameter/: 3 (after giving the radius of the circle, you can draw the circle)

change the order in which the cursor captures the two endpoints of the line to draw a circle on the other side of the line

suppose that the intersection of a circle and a straight line is used as the tangent of a circle. The operation process is as follows:

command: line

from point: int (capture intersection)

of

to point: cal

expression: int+3*nor (CEN, int)

select entity for int snap snap snap the intersection with the cursor)

select entity for Cen snap snap the center of the circle with the cursor)

select entity for int snap snap snap the intersection with the cursor, that is, draw the tangent of a known circle with a length of 3 from the intersection)

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