Making Spline and arc from Polyline in AutoCAD

You can convert geometry of spline to a polyline or an arc in AutoCAD with “Polyline Edit” or PEDIT command. This feature does not convert Polyline to spline or arc rather it gives them all the properties like anchor points and geometry keeping object type as Polyline.

In this article, I will show you how to do it using this sample geometry which is made with a polyline.

Make spline and arc from polyline in AutoCAD

1 – A simple geometry made with Polyline

Making Polyline look like spline:

Double click on a Polyline to start Polyline edit command or type PEDIT on command line press enter and select Polyline to start Polyline edit command.

Making Spline and Arc from polyline in AutoCAD 2

2 – PEDIT command line options

Now from command line select spline and press enter. This will make your Polyline look like a spline curve in such a way that vertices of original Polyline curve (shown with the green cross in image 3) will act as control vertices for the spline. The final geometry will look like image 3 shown below.

Make spline and arc from polyline in AutoCAD

3 – Polyline spline curve with control vertices indicated by green cross

Although using this method you can change the geometry of a Polyline to a spline but it will still remain a 2D Polyline. When you hover the cursor over this “spline” or check the property then AutoCAD will show it as a 2D Polyline.

You can also convert Polyline to true spline by using Polyline edit command, visit linked article to learn more.

Making Polyline look like Arc:

Double click on Polyline or use PEDIT to start Polyline edit then select Fit from options appearing on the command line.

Making Spline and Arc from polyline in AutoCAD 4

4 – Fit option on PEDIT command

The Fit option will convert your Polyline into series of tangentially connected arcs. Control points will be added to the geometry at the position where initially vertices of original polyline were present.

You can modify this new geometry using those control points or grips. In this case, also the Polyline will geometrically change to series of connected arcs but it will still remain a 2D Polyline.

Your final geometry will look like the one shown below.

Do you have any questions related to this tip? Let us know in the comments below.

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About the Author:

I am a mechanical engineer and I have worked with Design, Manufacturing and Training industries but now SourceCAD is my full-time work and I use it to train students all over the world. I also train corporate clients and help them develop the skill set of their workforce. I am Autodesk AutoCAD Certified Professional and an Autodesk expert elite member. I am a regular contributor of AUGI World magazine and apart from SourceCAD I also develop AutoCAD video courses for Pluralsight and other E-Learning businesses.

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