There is still another type of composite object that we can create with Autocad. It's about the regions. Regions are closed areas to which, due to their shape, physical properties are calculated, such as the center of gravity, so in some cases it will be convenient to use this type of objects instead of polylines or other objects.
You can create a region object from, for example, a closed polyline. However, they can also be created from the combination of polylines, lines, polygons and even splines, as long as they form closed areas in the same way. This versatility also allows us to create region objects using Boolean operations, ie adding or subtracting areas, or from the intersection of these. But let's look at this process in parts.
A region is always created from already drawn objects that form closed areas. Let's look at two examples, one of a polyline and one of simple objects clearly delineating an area.
The query of the physical properties of a region will be studied in chapter 26, while we can mention that we can also create regions from closed areas using the command "CONTOUR", although this command can also create polylines. Let's see the difference of one or the other.
We can also add two regions to a new one with the "UNION" command. Again, regions can first start from polylines or other closed forms.
The inverse Boolean operation is also valid, that is, one region subtracts another and obtains a new region as a result. This is achieved with the "DIFFERENCE" command.
The third Boolean operation is to intersect regions to obtain a new region. The command is "INTERSEC".