Building Objects with AutoCAD - Section 2

CHAPTER 5: GEOMETRY OF THE BASIC OBJECTS

A complex drawing is always made up of simple components. The combination of lines, circles, arcs, etc., allows us to create practically any form of technical drawing, at least in the field of two-dimensional drawing (2D). But the precise construction of these simple forms implies the knowledge of the geometry of these objects, that is, it implies knowing what information is needed to draw them. In addition, we will use here to study the commands that serve to create them and the options they offer.

5.1 Points

The most elementary object to draw is the point. To create it, it is enough to indicate its coordinates and although it is true that we can not create drawings using points, the truth is that they are often of enormous help as references when drawing other objects, such as lines and splines. We must also mention that in Autocad it is possible to configure the representation of points in a drawing.

Later, in this same chapter, we will return to the points, drawing them on the perimeter of other objects, with the Gradua and Divide commands.

5.2 Lines

The next object in simplicity is the line. To draw it, it is only necessary to determine the starting point and the end point, although the Autocad Line command also allows you to add line segments that start where the previous one ends. If there are several segments drawn, we can even join the end point of the last one with the first and close the figure. In English, the command is written LINE.

Let us now draw the following sequence of coordinates.

Command: line

Specify first point: 0.5,2.5
Specify next point or [Undo]: @ 2.598 <60
Specify next point or [Undo]: 2.5,4.75
Specify next point or [Close / Undo]: @ .5 <270
Specify next point or [Close / Undo]: @ 1.25 <0
Specify next point or [Close / Undo]: @ .5 <90
Specify next point or [Close / Undo]: 4.75,4.75
Specify next point or [Close / Undo]: @ .5 <270
Specify next point or [Close / Undo]: @ 1.25 <0
Specify next point or [Close / Undo]: @ 0, .5
Specify next point or [Close / Undo]: 6.701,4.75
Specify next point or [Close / Undo]: 8,2.5
Specify next point or [Close / Undo]: 6.701, .25
Specify next point or [Close / Undo]: 6, .25
Specify next point or [Close / Undo]: @ 0, .5
Specify next point or [Close / Undo]: @ -1.25,0
Specify next point or [Close / Undo]: @ 0, -0.5
Specify next point or [Close / Undo]: @ -1,0
Specify next point or [Close / Undo]: @0,0.5
Specify next point or [Close / Undo]: 2.5,0.75
Specify next point or [Close / Undo]: @ 0, -0.5
Specify next point or [Close / Undo]: 1.799,0.25
Specify next point or [Close / Undo]: c

Obviously, it will be rare for us to have the coordinates at the moment of drawing. The actual practice of drawing implies the use of relative (Cartesian and Polar) coordinates, as well as the position of other objects already drawn using references to objects and other drawing tools, as will be studied at the time.
The issue to highlight here is that Autocad requests the determination of the next point to draw a new line segment and we can respond with a "click" on the screen, with an absolute or relative coordinate or using some of its options. For example, if instead of a point we indicate the letter "H" for "unDo", Autocad will delete the last line segment, as we saw in the video. On the other hand, the letter “C” (“close”) joins the last line segment with the initial one and this option appears among its options once we have drawn two or more line segments.

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