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Benefits of Polylines
Tip# 4183 By Danny Korem On 16-Sep-2013
Rated By 1 users
Categories : Polylines
Software type : AutoCAD 2014
Rename File To : No Files to download.
Polylines provide more control, and more display possibilities, than lines and arcs.

Tipster Danny Korem discusses why he prefers to use polylines in AutoCAD, as opposed to lines and arcs.

"Polylines are line and arc sequences that can be created in various ways: One can just use the Polyline command and draw a series of segments (lines or arcs), or one can select a line or an arc using the Pedit option, change the selection to be a polyline, and join other adjacent segments to create a polyline. A polyline can also be created by the use of bpoly or boundary (with island detection) just by clicking within geometry.

"Benefits of polylines include the following:

  • When a polyline is created, a vertex is created between two segments, and nothing has to be done to force two endpoints of the two line objects to be coincident. Furthermore, the first point of the first segment will dictate a uniform z value governed by a polyline's property — the elevation, which can be modified at all times.
  • From the moment a polyline contains more than one segment, the area becomes a property.
  • In the latest versions of AutoCAD, hovering over a pline vertex will offer options to add or remove vertex and the long midpoint grips offer change to arcchange to line functionality.
  • One or more selected polylines can be closed or opened by changing the closed property from no to yes, and vice versa.
  • When Overkill is used on a polyline, it might simplify it by reducing the number of vertices/segments to minimum (if a vertex is between two collinear segments) without affecting the geometry's shape.
  • If a geometry is to be flattened to a certain z value, selected polylines can all be at a specific elevation in no time.
  • Important design info such as length (perimeter) and area are derivatives of polylines without no need to calculate anything.
  • I don't consider it a huge advantage, but line width can be applied on plines only."

Notes from Cadalyst tip reviewer Brian Benton: Polylines are very versatile. They provide more control, and more display possibilities, than "regular" lines and arcs. They also behave differently; because they are a series of connected lines/arcs (or segments), they have features that lines/arcs cannot have. They also function without any special parametric or geometric controls.


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User comments
Comment by Cooper,Kent
Posted on 2013-09-16 09:15:33
Some other benefits: 1) One that may not mean as much today as it did in the early days when memory was expensive: Polylines (beyond a very small number of segments) use LESS MEMORY than the equivalent separate Lines and Arcs would. AutoCAD needs to keep information about Layer, Color and/or Linetype and/or Linetype Scale and/or Lineweight overrides if any, Elevation, Thickness, etc., only ONCE for the entire Polyline entity, rather than individually for every separate Line and/or Arc entity. Also, for Lightweight Polylines, since the Elevation controls the Z coordinates of all vertices, it stores only two coordinates (X & Y) for all vertices. 2) The option for linetype generation to flow across vertices (around corners, etc.), means that a non-continuous linetype can be apparent even within segments that, on their own, would show as continuous because they're too short for the non-continuous linetype's pattern cycle.
Comment by Somppi,Robert
Posted on 2013-09-16 13:25:18
Polylines have their place but too many times I've seen them inappropriately used and often get in the way of good drafting practices when it comes to making changes.
Comment by Somppi,Robert
Posted on 2013-09-16 13:25:43
Polylines have their place but too many times I've seen them inappropriately used and often get in the way of good drafting practices when it comes to making changes.
Comment by Tulis,Ralph
Posted on 2013-09-17 10:13:20
And this is new because? I have been using polylines since the first became an AutoCAD entity. The benefits are numerous - the initial benefit for me was 2-fold: 1) the ability to add line width, and 2) the ability to offset aa parallel polyline. Never mind the attributes include with them (area, overall length, the ability to Divide a complex line into equal lineal distances). My only grip using 2012 is that when editing vertices the scroll wheel functionality is lost if the Pedit menu is visible on the screen. I would agree with the comment that Plines can be over-used at time. Straight one-segment Plines offer no advantage over a simple Line (unless line width is needed).
Comment by Elrod,K
Posted on 2013-09-17 10:20:39
Some of the benefits of lines over plines: If plines are drawn with widths in a drawing then you can't control the width in other drawings when Xrefing them. Lines can be easily checked with LIST or PROPERTIES for the angle they are drawn at, plines can't. Length of lines can be modified with the change command, plines cannot. Multiple lines can be brought to one point quickly with change, plines cannot. Lines can be straightened to align with Ortho quickly with Change command, plines cannot. All options of the LENGTHEN command will work on lines, the options of DElta, Percent and Total will work on a pline, the DYnamic option will not work on plines. Hover over the end grip on a line you will get a choice of lengthen or stretch. Lengthen will extend the length dynamically and keep the line at the same angle. JOIN command won't work on plines unless the ends are exactly touching, lines don't need to be touching for join to work. A line inherits the elevation of the object that it is snapped to at each endpoint, handy when working in 3D. Start the line command, then type tan, pick an arc, notice how the line start point will move dynamically as you move the cursor, a pline will not do that. Parallel lines can be filleted, plines cannot. Use plines or lines depending on the need, they both have their benefits over the other. Using one exclusively limits you.

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