Making a polygon

Polygons are closed geometries made with three or more sides. The smallest polygon is a triangle and the largest polygon is a circle, which is made up of an infinite number of sides.

In AutoCAD, you can make a polygon with a minimum of 3 and a maximum of 1,024 sides:

Figure 2.45: The Polygon command in the Draw panel

The Polygon tool is in the Draw panel of the Home tab in the expanded rectangle flyout, as in the preceding screenshot. Before we start making a polygon, we need to learn about the two types of polygon options, namely inscribed, and circumscribed, in AutoCAD.

Inscribed and circumscribed polygons

When you use the polygon command, you are presented with the inscribed and circumscribed options, so before we dig deeper into the polygon tool, let's understand what inscribed and circumscribed geometries are.

In the following diagram, the first polygon is inscribed in a circle with a radius equal to the length of the green line. In this case, the vertices of the polygon are touching the circumference of the circle.

In the second case, the polygon is circumscribed about the circle, which has a radius equal to the length of the green line and in this case, the midpoints of the sides of the polygon are touching the circumference of the circle:

Figure 2.46: The polygon inscribed and circumscribed about a circle

When making polygons, AutoCAD will prompt you to specify the radius of the polygon, which is essentially the radius of the inscribed or circumscribed polygon. The type of polygon that you need to make depends on the dimensions provided in the drawing.

Making polygons

So, now that you know what an inscribed and a circumscribed polygon are, we are ready to make our first polygon. In this case, I will make a pentagon, which is a polygon with five sides, and I will use a polygon inscribed in a circle:

1. Select the Polygon tool from the Draw panel of the Home tab, or type POL and press Enter.
2. The command line will now prompt you to specify the number of sides of the polygon. Type 5 and press Enter.
3. Now, the command line will prompt you to specify the center of the circle. Click on a point in the drawing to specify the center.
4. Now, the command line will prompt you to specify the type of polygon: Inscribed in circle or Circumscribed about circle:

Figure 2.47: The inscribed and circumscribed options in the Polygon command

5. Select Inscribed in circle for this case.
6. Now, the command line will prompt you to specify the radius of the circle. Enter 5 as the radius and press the Enter key.

You will notice that an inscribed polygon with a radius of 5 units will be rendered. In this case, the radius of the polygon is the radius of the inscribed circle that this polygon is made in.

You can use a similar process to make a polygon that is circumscribed about the circle. Although these two options may seem like the only options for making a polygon in AutoCAD, its not always possible to have the radius of inscribed or circumscribed circles. If you only have the side length of the polygon, then you can use this next method to make a polygon using the side length.

In this example, I will make a hexagon with the length of its sides as 6 units:

1. Start the Polygon command from the Draw panel or use its POL command.
2. Now, the command line will prompt you to specify the number of sides. Type 6 and press Enter.
3. Now, the command line will prompt you to select the center of the polygon, but in this case, select the Edge option from the command line:

Figure 2.48: The Edge option in the polygon command line

4. Now, specify the first point of the edge by clicking anywhere in the drawing area.
5. You will notice that the cursor will now follow the edge of your polygon. Simply click on the second point to make a polygon of a required length, or specify the length in the command line and press Enter:

Figure 2.49: A hexagon made with the Polygon command

A polygon with the required edge length will be made. In this case, you were not required to specify the inscribed or circumscribed circle as the reference.

Now that we know about some of the basic draw tools that make a drawing, let's move on to learning about a few of the basic modify tools.