A polyline is a connected sequence of line segments created as a single object. You can create straight line segments, arc segments, or a combination of the two.
Some reasons you may choose to use polylines include the following:
- Vertices remain joined even after grip editing
- Absolute line width (as an alternative to relative lineweight) that can be constant or tapered across a segment
- Move and copy a polyline as a unit
- Easily create rectangles and polygons as single objects
- Smart application of non-continuous linetypes across vertices
- Easy extrusion for 3D solids in AutoCAD
Modifying Polylines
Several methods are available to change the shape and appearance of a polyline.
When you select a polyline you can use grips to move, add, or delete individual vertices, and convert between arc and straight segments.
You can also convert a polyline to a spline-fit or curve-fit polyline.
Use the PEDIT command to change the width of an individual segment or the entire polyline.
Linetypes and Polyline Vertices
For polylines, you can specify whether a linetype pattern is centered on each segment or is continuous across vertices throughout the entire length of the polyline.
Use the PLINEGEN system variable to specify this option for new objects. You can update existing polylines on the Properties palette in the Linetype Generation setting.
Polyline Format: Lightweight vs "Legacy" Polylines
A lightweight polyline is defined as a single object that contains information defining each of the polyline's vertices, unlike "legacy" polylines, which are defined as a collection of many objects that define each of the polyline's vertices. A "legacy" polyline can be either a 2D or 3D polyline, while a lightweight polyline can only be a 2D polyline.
Lightweight polylines display faster and consume less disk space and RAM than "legacy" 2D polylines. As of AutoCAD Release 14 and later, 3D polylines are always created as "legacy" polyline entities, and 2D polylines are created as lightweight polylines unless they are curved or fitted with the AutoCAD PEDIT command. When a drawing from an earlier release is opened in AutoCAD Release 14 or a later release, all 2D polylines are converted to lightweight polylines automatically, unless they have been curved, fitted, or contain extended data (xdata).