The offset command is a tool I use often for creating geometry; it’s particularly useful when the drawing consists of a lot of parallel lines. The command includes a few lesser known options, and by using an obscure system variable, you can make it even more versatile.
The command includes a layer option. Type “L” at the initial offset command prompt, then type “C” to toggle from the default “Source” to “Current”, and all objects produced using the offset command will be created on the current layer, as opposed to the original object’s source layer. This option is retained, just like the offset distance, throughout your current AutoCAD session.
The system variable OFFSETGAPTYPE controls how AutoCAD deals with the potential gaps created when offsetting the segments of a polyline or polygon, such as a rectangle. Without this feature, an offset rectangle would yield four line segments equal in length to the originals, with “gaps” in each corner. This is what happens if you offset four independent lines:
The offset command solves this problem with polylines and polygons by filling in these “gaps”, and how it fills in these “gaps” is controlled by the system variable called OFFSETGAPTYPE.
OFFSETGAPTYPE is set to “0” by default, which causes the line segments of a polyline or polygon to extend to sharp corners.
If you change it to “1”, any potential gaps will be filleted, with a radius equal to the offset distance. This is actually a more geometrically correct way to offset, as all points on the new object will be the same distance from the original.
Change OFFSETGAPTYPE to “2”, and the vertices will be chamfered.
Changes to this system variables are “permanent”, in that they are retained from one AutoCAD session to the next. I leave mine set to “1”, so that it typically fillets the vertices.
