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Drawing commands

So far, the only drawing command we have used is the ‘line’ command. But why shall we draw a square or rectangle by drawing four lines when we have the ‘rectangle’ command available? And how do we draw a circle, an arc and an ellipse? In this tutorial we will learn various simple drawing commands and the different ways to use them.

Polylines

Command for polyline: pline or pl

Polylines are just like lines but more powerful. The first difference to notice between a line and a pline is that polylines drawn in one command are connected together as a single entity. Let us try this out to better understand; follow the command sequence shown below:

Command: l
LINE Specify first point: 50,50
Specify next point or [Undo]: @50,0
Specify next point or [Undo]: @0,50
Specify next point or [Close/Undo]: @50,0
Specify next point or [Close/Undo]:
Command: pl
PLINE
Specify start point: 150,50
Current line-width is 0.0000
Specify next point or [Arc/Halfwidth/Length/Undo/Width]: @50,0
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @0,50
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @50,0
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:


Zoom to ‘Extents’ and your drawing should look like the one in the diagram.

Now you may already have noticed that we have drawn the first s shape using the line (l) command and the second s shape using the pline (pl) command. Move your cursor over the first (line) drawing; select the lines and you notice that each of them will be selected individually. On the other hand, if you try to select the pline drawing, the whole of it will be selected as one entity.


Also note that with polylines you are presented with further options while you are drawing. Always notice the options given in the square brackets [ ] while using commands; these will let you know what you can do with the command being performed. Let us have a look at the square brackets in the pline command:

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:

As we learnt earlier, typing the first letter/s, that are in uppercase will switch your command into that mode or perform that command option. For example if we type ‘a’ the pline will switch into arc mode, and if we type ‘c’ a final line will be drawn to the first point in the pline sequence and the command will be terminated. Try to draw different polylines and explore the various options given. Remember to always read the square brackets, they will lead you in the right direction and you will be drawing complex polylines in no time. Here is an example of what you can do:

Arcs

Command for arc: arc or a

You can draw arcs in various ways. The default option while drawing an arc is to define three points; the starting point, a point the arc passes through, and the end point. Type the command ‘a’ and click any three points on the screen. Wasn’t that easy!

Let us now explore some more ways to draw arcs. In the command example given below, absolute coordinate entry has been used. Also, instead of specifying three points on the screen, a starting point has been specified, then a different option ‘center’ has been chosen by typing ‘c’. This allows the center of the arc to be specified, and finally we are prompted to specify the end point of the arc:

Command: a
ARC Specify start point of arc or [Center]: 150,100
Specify second point of arc or [Center/End]: c
Specify center point of arc: 100,100
Specify end point of arc or [Angle/chord Length]: 50,100

Notice that you can also specify the included angle (a) or the chord length (l) rather than the end point of the arc. Practice the various ways of drawing arcs until you are comfortable with this command.

Circles

Command for circle: circle or c

Like arcs, circles can also be created in various ways. The default option is to specify the center point of the circle and its radius. Follow the command line example:

Command: c
CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 100,100
Specify radius of circle or [Diameter]: 50

This command sequence draws a circle with center point 100,100 and a radius of 50. ACAD will conveniently store the radius you have entered in memory so if you draw another circle, when you come to specify the radius you will be asked if you wish to keep the same radius as before. Try to draw another circle:

Command: c
CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 200,100
Specify radius of circle or [Diameter] <50.0000>:

Notice the last command line. The user is being prompted to specify the radius or opt to specify the diameter. Finally the user is given another option <50.0000>; this is the radius we have specified for the previous circle. To select this option just press enter and another circle with radius 50 is drawn. This speeds up the process of drawing circles of the same size because you don’t have to specify its size every time you draw another one. It may seem trivial at this point but keep in mind that time is precious, and faster ways of doing things mean faster production rates and these make a difference between an ACAD user and a better ACAD user.

Let us explore the different options we are presented while drawing a circle; [3P/2P/Ttr (tan tan radius)].

  • The option ‘3P’ allows us to specify three points on the circles circumference rather than the default center and radius option.
  • The option ‘2P’ allows us to specify two points on the circle’s circumference that are diametrically opposite.
  • The option ‘Ttr’ allows us to specify two tangents to the circle and its radius. To better understand this option, a command line example is shown below. In this example two lines are drawn at 90 degrees to each other and a circle of radius 50 is drawn tangential to both of these lines:



Command: l
LINE Specify first point: 100,200
Specify next point or [Undo]: @100<-90
Specify next point or [Undo]: @100<0
Specify next point or [Close/Undo]:

Command: c
CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: t
Specify point on object for first tangent of circle: select one of the lines
Specify point on object for second tangent of circle: select the other line
Specify radius of circle <50.0000>:

Ellipses

Command for ellipse: ellipse or el

Follow the command example given to draw an ellipse using the default options:

Command: el
ELLIPSE
Specify axis endpoint of ellipse or [Arc/Center]: 100,100
Specify other endpoint of axis: @200,0
Specify distance to other axis or [Rotation]: 40

This will draw an ellipse with a horizontal major axis of 200 and a minor axis of 80. Notice that the last dimension specified is 40, this is half the minor axis. Also notice that ellipses can be drawn at any angle and not just horizontally:

Command: el
ELLIPSE
Specify axis endpoint of ellipse or [Arc/Center]: 100,100
Specify other endpoint of axis: @200<60
Specify distance to other axis or [Rotation]: 40

This will draw the same ellipse rotated by 60 degrees in an anticlockwise direction about its endpoint. You can also opt to specify the center of the ellipse or to draw an elliptical arc rather than a complete ellipse. Explore the various options as you have done with the pline and circle commands.

Rectangles

Command for rectangle: rectang or rec

The rectangle command defaults require you to specify two diagonally opposite corners of the rectangle. Options that can be specified for the rectangle are to have chamfered or filleted corners and line width amongst others.

Polygons

Command for polygon: polygon or pol

The options for drawing polygons should be very straight forward now that you have a good grasp of the way drawing commands work. Let us go through an example:

Command: pol
POLYGON Enter number of sides <4>: 6
Specify center of polygon or [Edge]: 100,100
Enter an option [Inscribed in circle/Circumscribed about circle] :
Specify radius of circle: 50

First the command ‘pol’ has been entered, and we are prompted to specify the number of sides. In the example six sides have been specified. Next we have to specify the center of the polygon, in this case 100,100 and then for the next dimension we are asked to opt for either inscribed in circle or circumscribed about circle (the default being inscribed). By opting for inscribed, you will then be asked to enter the ‘radius of circle’ which is the same as the distance from the center to a corner of the polygon. If we opt for circumscribed, we will also be asked for the radius of the circle but this time the radius is the same as the distance from the center to the face of the polygon.



Points

Command for point: point or po

Last but not least, let’s draw some points. The command sequence is very straight forward:

Command: po
POINT
Current point modes: PDMODE=0 PDSIZE=0.0000
Specify a point: 100,100

Can you see the point? Yes it is there! Look at the point you specified, in this case 100,100. There it is. So what if you want to draw a hundred of them and keep track of where they are? Simple, look at the command window sequence and notice that PDMODE and PDSIZE are both set to zero. Let us change the pdmode first. This is called a system variable (more about those later), and it can be set to 0, 1, 2, 3 or 4. Try the different settings, and take your pick. Any points that you draw from now on will be displayed in this way and every time you change the pdmode, all points will be updated.

The pdsize is responsible for the size of the point. If it is set to ‘0’ as it is by default, then the point is drawn at 5% the size of the drawing area height. If it is set to a number larger than ‘0’ points are drawn at that size. If it is set to a size smaller than ‘0’ thus a negative number, points are drawn as a percentage of the viewport’s size equal to that number.

Hooray! We can draw, we can draw almost anything! And soon we will be drawing more complex stuff. Let us practice what we have just learnt with some drawing exercises. Off we go…


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