topic Re: Difference between line, arc, spline, polyline in AutoCAD Forum

Difference between line, arc, spline, polyline

Anonymous — Sat, 13 Feb 2021 07:41:18 GMT

Hello everyone. Here is Autocad Newbie!!!!

Using command 'pedit', it says, changing line, arc, spline into polyline[Y/N]

I don't know difference between them.!!!!

Why should I change them into polyline.

Please record the reason for poor Newbie.

Thank you.

Re: Difference between line, arc, spline, polyline

Moshe-A — Sat, 13 Feb 2021 08:18:12 GMT

@Anonymous ,

when you have a free lines and arcs that has a common point like a chain of lines, you can turn them into a polyline and to do that you use PEDIT command. turning them to a polyline will let you to get the area \ perimeter.

if you already have a polyline, you can EXPLODE it and release them to be free lines + arcs.

moshe

Re: Difference between line, arc, spline, polyline

Kent1Cooper — Sat, 13 Feb 2021 11:42:43 GMT

In the PEDIT command, if you select a Polyline, it will just go to the editing prompt, because the P in PEDIT is for Polyline, so it knows that's what you want to do. If you select one [or some] of those other things, it needs to convert it [or them] into a Polyline [or Polylines] so that it can use the Polyline-editing operations on it [them]. By default, it asks you whether you want to convert them, just to be safe. If you know that you will always want to convert anything you select in PEDIT, you can set the PEDITACCEPT System Variable to 1, and it will not ask you that question any more.

Re: Difference between line, arc, spline, polyline

leeminardi — Sat, 13 Feb 2021 13:25:01 GMT

In AutoCAD the following terms are used for specific entity types:

Line = a single straight line that goes from one x,y,z location to another x,y,z location. If z =0 for the two endpoints the line is considered to be 2D.

Arc = a single arc (a portion of a true circle). It may lie on the XY plane or can be positioned in any 3D orientation.

Spline = a smooth curve that may lie on a 2D plane or can wander in 3D space.

Polyline = a series of straight line and arc segments that define a single AutoCAD entity. All the segments of a polyline lie on a 2D plane although that plane may be at any orientation in 3D space. If the polyline contains arc segments their ends will be tangent to the adjacent line or arc segment.

Polylines are useful for a variety of applications. They are used to define a path or a single closed shape. For example, you could construct a hexagon with 6 lines or 1 polyline. Pedit can be used to convert the 6 lines to one polyline. When using pedit and selecting one of the 6 lines AutoCAD will ask you if you want to convert the first line to a polyline at which point you respond "yes" and then select the other 5 lines. The result will be a closed polyline. Explode is used to convert a single polyline to a collection of lines and arcs.

Re: Difference between line, arc, spline, polyline

Kent1Cooper — Sat, 13 Feb 2021 17:58:39 GMT

@leeminardi wrote:

.... If the polyline contains arc segments their ends will be tangent to the adjacent line or arc segment. ....

Not necessarily. If you draw it by simply picking points in Arc mode, under the default Endpoint option [or the Angle or CLose options], or if you apply the Polyline option in FILLET to a Polyline, that's what you'll get. But there are options to aim the beginning of the arc segment in any Direction you want as you draw, or to specify a Second point [followed by a third] as you would draw a three-point Arc object, or the CEnter, any of which can result in the arc segment not being tangent from the previous segment, but it's still part of the same Polyline. And even if an arc segment was drawn tangentially, you can make it non-tangent by grip-editing, or PEDIT's Edit Vertex. option, or STRETCH, or some other means. Read about it all in Help.

Re: Difference between line, arc, spline, polyline

Kent1Cooper — Sat, 13 Feb 2021 18:00:55 GMT

@leeminardi wrote:

.... When using pedit and selecting one of the 6 lines AutoCAD will ask you if you want to convert the first line to a polyline at which point you respond "yes" and then select the other 5 lines. ....

... only if PEDITACCEPT is set to 0.

Re: Difference between line, arc, spline, polyline

leeminardi — Sat, 13 Feb 2021 19:45:40 GMT

@Kent1Cooper wrote:
@leeminardi wrote:
.... If the polyline contains arc segments their ends will be tangent to the adjacent line or arc segment. ....
Not necessarily. If you draw it by simply picking points in Arc mode, under the default Endpoint option [or the Angle or CLose options], or if you apply the Polyline option in FILLET to a Polyline, that's what you'll get. But there are options to aim the beginning of the arc segment in any Direction you want as you draw, or to specify a Second point [followed by a third] as you would draw a three-point Arc object, or the CEnter, any of which can result in the arc segment not being tangent from the previous segment, but it's still part of the same Polyline. And even if an arc segment was drawn tangentially, you can make it non-tangent by grip-editing, or PEDIT's Edit Vertex. option, or STRETCH, or some other means. Read about it all in Help.

@Kent1Cooper I misspoke! An arc in a polyline need not be tangent to an adjacent line or arc. I was thinking of the common construction of a polyline when you add sequential arcs. It is possible to not make them tangent. Thank you for the clarification. The main goal of my post was to provide the OP a definition of lines, arcs, and polyline entities to complement the behavior definitions that were provided.