I know what you’re thinking but in AutoCAD, BO is anything but stinky! BO is the command alias to launch the BOUNDARY command, which was introduced in AutoCAD Release 13… or was it R12? Anyway, it’s a valuable (and little known) byproduct of the BHATCH (boundary hatch) command and I think you’ll recognize the similarities!
The BOUNDARY command displays the Boundary Creation dialog box. You can also use the dash “-“ to access the command line version (-BOUNDARY). Choose Pick Points to pick a point in the drawing. AutoCAD automatically determines the boundary using the same underlying technology that is uses when you pick a point to create a hatch. Notice that you can even specify island detection, similar to creating a hatch.
Instead of creating a hatch, however, the BOUNDARY command creates a polyline. Why would you want to create a polyline? Many reasons! In my previous post, for example, I wanted to determine the area of a floor plan. Unfortunately, picking all the boundary points with the AREA command was cumbersome and inaccurate. Using the BOUNDARY command, I can quickly create a polyline boundary and then use the AREA command to select the polyline! Finding the enclosed area of the floorplan using the AREA command went from 40 point picks to a single object selection! And, not only does it save time, but it’s more accurate because it accounts for the curve and small jogs in the wall.
Various controls in the Boundary Creation dialog box offer additional flexibility for creating boundaries. For example, instead of creating a polyline boundary, you can set the Object type to Region. A region looks similar to a polyline but has mass properties and other “solid” properties. Maybe I’ll discuss regions in a future post.
In order for AutoCAD to determine the boundary surrounding the selected point, it analyzes all the objects in the current display. If you try to create a boundary or hatch with an excessive amount of objects displayed, AutoCAD warns you and asks if you want to proceed.
In many cases, you can simply zoom in to display only the area in which you are interested. For example, to create the boundary of the apartment in this floor plan, I could zoom into the highlighted area and AutoCAD would have no problem analyzing those objects, quickly.
As an alternate, you can manually limit the objects that AutoCAD analyzes during the boundary detection by specifying a boundary set in the Boundary Creation dialog box.