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Thread: '2D polyline' & 'polyline' What's the difference?

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  1. #1
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    Default '2D polyline' & 'polyline' What's the difference?

    Hi

    I've got a combination of two types of entity - '2D polyline' & 'polyline'.in a dwg.

    For some reason they display different context menus when I select them & right-click.
    They were created the same way I think, individual lines joined using pedit.

    I've got the PLINETYPE system variable set to 2 so they're all optimized to 2d.

    When I use the CONVERT command it converts the '2d Polylines' into 'polylines'. Which is what I want.

    However, I still don't understand how I created the '2D polylines' & why , having PLINETYPE set to 2 it didn't convert when I reopened the dwg.

    I still don't understand what the difference between the two is. They have no Z values & are in the world UCS plain, just at different elevation, which, as I understand it, doesn't make any difference.

    Any ideas?

    Thanks for your help.

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    If you draw a simple polyline (i.e. LWPOLYLINE) it's just a "polyline" in the properties box. If you then spline the line from the PEDIT command, it turns the normal LWPOLYLINE into a POLYLINE (listed) and shows up as a "2D Polyline in the properties box. I assume AutoCAD does this so it can perform different operations on each entity???

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    Quote Originally Posted by Coolmo View Post
    If you draw a simple polyline (i.e. LWPOLYLINE) it's just a "polyline" in the properties box. If you then spline the line from the PEDIT command, it turns the normal LWPOLYLINE into a POLYLINE (listed) and shows up as a "2D Polyline in the properties box. I assume AutoCAD does this so it can perform different operations on each entity???
    Thanks for the reply.

    I must have done something else because I wouldn't touch splines with a barge pole.

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    I attach an example.

    Apart from the the entity name (& the location, obviously), can you spot the difference?

    AutoCAD (well, specifically ADT) treats them differently.

    Thanks

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    Interesting point here......I didn't know there was another type of polyline.

    I agree, splines are nasty!

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    the're not really SPLINEs as in the entity SPLINE but splined polylines. I use them all the time when drawing out contours but make sure I break or trim them down so you actually get all the grips of every point inside the polyline. I NEVER leave anything splined... causes too much trouble.

    Looking further into a 2D polyline and LWpolyline when they're listed, you'll notice that each vertex of the 2Dpolyline has its own Handle (in addition to the entity's handle) whereas the regular LWpolyline only has one handle as the entity handle. I assume that all polylines use to be 2Dpolylines back in the day (R14) and when they came out with the LWpolyline to save space, they noticed they still needed the properties of the 2Dpolyline to perform splines and such on them. The last part here is pure speculation on my part though

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    Default Re: '2D polyline' & 'polyline' What's the difference?

    Quote Originally Posted by Dave F. View Post
    Hi

    I've got a combination of two types of entity - '2D polyline' & 'polyline'.in a dwg.

    For some reason they display different context menus when I select them & right-click.
    They were created the same way I think, individual lines joined using pedit.

    I've got the PLINETYPE system variable set to 2 so they're all optimized to 2d.

    When I use the CONVERT command it converts the '2d Polylines' into 'polylines'. Which is what I want.

    However, I still don't understand how I created the '2D polylines' & why , having PLINETYPE set to 2 it didn't convert when I reopened the dwg.

    I still don't understand what the difference between the two is. They have no Z values & are in the world UCS plain, just at different elevation, which, as I understand it, doesn't make any difference.

    Any ideas?

    Thanks for your help.
    I have found that AutoCAD drawings that are exported from other products i.e. Inventor, create a lot of 2d Polylines. Converting 2d polys to polylines reduces file size dramatically.

    Could this be the reason? After I run the convert command, I run "Overkill" which picks up (some of) the duplicates.

    Roy

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    Red face Re: '2D polyline' & 'polyline' What's the difference?

    I have been having a similar problem, but this may be a separate thread. I am working in LT 2008 and the program spontaneously started making polylines with just one handle. Sometimes. I can draw several plines with no problem, then the next one has just one handle. I am picking the button on the tool panel, not doing anything different. Rectangles have one handle too.

    I did't understand the discussion about pline vs wlpline although I did check that 'plinetype' is set to 2.
    I should note that I am working on a Mac using Fusionware to toggle to windows so I can run AutoDAD. I'll try a reboot, that sometimes helps work out the Mac/PC culture clash.

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