Centerline Between Polylines in AutoCAD: Quick and Easy Tutorial

In this blog post, we will look at how to draw a centerline between two polylines in AutoCAD. Creating a symmetric line between polylines in AutoCAD is essential for achieving precision in design projects. Whether in architecture, engineering, or drafting, a centerline helps ensure accurate measurements. Mastering this technique streamlines your workflow, and saves a lot of time.

CENTERLINE Command

AutoCAD has a built-in command called CENTERLINE, it creates a centerline geometry associated with previously selected lines and linear polyline segments. A centerline is generated at the apparent midpoint between the start and endpoints of the two selected lines. For nonparallel lines, the centerline is drawn between the endpoints and the imaginary point where the lines would intersect.

To use it follow the steps below:

1. Activate the CENTERLINE Command by typing CENTERLINE on the command line.
2. Secondly, select the first Line or linear polyline you want to use.
3. Then, select the second Line or linear polyline you want to use.

AutoCAD will automatically create a centerline object between the two lines!

The downside of this command is that it can only create a middle line between two line segments.

If you need a middle line between polylines with multiple segments, it won’t do the trick. This can be done with a LISP as discussed below.

Centerline between two Polylines in AutoCAD

In the first paragraph, we’ve looked at a predefined command CENTERLINE, here we will use a LISP that can expand the functionality of that command and create a Polyline between two Polylines no matter how many vertexes you have.
To use that routine follow the steps below:

• First, download the attached PathAverage.zip file and unzip it.
• Secondly, in the AutoCAD command line, type APPLOAD and press Enter.
• A window will pop up, there, browse for the PathAverage.lsp file and click Load.
• Then, type in PAV in the command line and press Enter.
• Now, AutoCAD will ask you to define the number of segments to divide the path. Enter a number you feel appropriate.
• Lastly, choose the first and second polylines from the drawing for averaging.

AutoCAD will draw a polyline that approximates the middle of the two polylines. The results may vary in relation to the number of segments you specify in step 5.

Mastering the technique of drawing a centerline between Lines/Polylines in AutoCAD is a great way to achieve better designs faster and with less effort. Whether using the built-in CENTERLINE command or leveraging custom LISP, understanding this process enhances your workflow and ensures more accurate, professional results for your projects.

I hope you find this post a value, you can check our other AutoCAD Articles to find even more interesting tips and tricks.