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Offset not working in one direction

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Message 1 of 22
GPSJane
9197 Views, 21 Replies

Offset not working in one direction

I have a polyline that meets itself back at the beginning. It should be closed and appears to be. I joined several lines to get the polyline. When I try to offset it I can only offset towards the inside and not the outside. Is there a reason for this or am I doing something wrong?

21 REPLIES 21
Message 2 of 22
jggerth1
in reply to: GPSJane

>> It should be closed and appears to be.

 

Appearance doesn't mean much when it comes to open or closed Plines.  What do PEdit or the Properties palette say?

 

WBlock out the pline, and post is as a dwg here so we can look at it.  Generally when I have a non-offset-able pline it's because of overlapping segments/duplicate vertices.  You could use the Properties palette and scroll though the vertex numbers and see where/how the marker jumps to.

Message 3 of 22
GPSJane
in reply to: jggerth1

To be honest I have no idea what you just said, except the part about posting here. Ok how do I get the list of vertices to scroll through? In properties inspector I only get normal properties.

Message 4 of 22
GPSJane
in reply to: GPSJane

I figure out the WBLOCK thing but now I get an error here when I try to post: "The contents of the attachment doesn't match its file type."

Message 5 of 22
GPSJane
in reply to: jggerth1

Actually does it need to be closed for offset any way?
Message 6 of 22
jggerth1
in reply to: GPSJane

Try zipping up the drawing and attaching that.  usually works better here....

 

to close or not to close -- you're right that it's not needed for offsetting,  but closing and open pline (or opening a closed one) may show you where the problem is.  the basic rule though on closed vs open is that you can't trust your eyes.  even a pline that starts and ends on the exact same point is not necessarily closed.

 

to step through the vetices of a pline, there are two basic ways.  Select the Pline, and in the property palette, look at the start of the Geometry section.  Click on the number that's showing, and a pair of <> arrows will appear.  click on one of them, and you'll see the geometry information change, and an 'X' marker move along the pline.  Keep clicking, and see of the X sticks in one spot, or jumps backwards.  If it does, that's your problem area to be repaired.

 

Second way would be to run the PEDIT command, select the pline, enter "E" for the Edit Vertex option, and use N (next) and P (previous) to step through the vetices.

 

One option you might want to try  with your original problematic Pline is to offseet it towards the middle, since that works, and then try offsetting _that new Pline_  to the outside while doubling the distance.  dunno - but it might work....

 

Message 7 of 22
GPSJane
in reply to: jggerth1

JGerth thanks so much for the help.

 

The Geometry section shows insertion points for x, y and z and scale for x, y and z but no numbers or arrows. When I do PEDIT and it says 'select polyline' it just does nothing when I click on it. I don't understand! And I have a headache now.

 

Why is this so difficult?

Message 8 of 22
GPSJane
in reply to: GPSJane

Oh I forgot this.

 

Message 9 of 22
dmfrazier
in reply to: GPSJane

No, it doesn't need to be closed for offset to work in both directions, so it seems something unusual must be at play.

Since you are having trouble attaching a file (not unusual), if the polyline only has a few vertices, try entering "LIST" on the command-line, select your problem polyline, hit Enter, and then copy the results from the command-line window into a reply.  That might reveal a clue.

Message 10 of 22
GPSJane
in reply to: dmfrazier

I get the same problem; if I type LIST then it askes me to select an object but it does nothing just keeps asking e to select an object when I click on it. Its like I'm going backward.

 

I did attach that file above though, zipped.

Message 11 of 22
jggerth1
in reply to: GPSJane


@AutoDesk wrote:

JGerth thanks so much for the help.

 

The Geometry section shows insertion points for x, y and z and scale for x, y and z but no numbers or arrows. When I do PEDIT and it says 'select polyline' it just does nothing when I click on it. I don't understand! And I have a headache now.

 

Why is this so difficult?


Make sure you're not in paper space and the pline is in model space, or vice-versa....

 

Why is this so difficult?  You're using an incredibly complex piece of software, developed for over twenty years, that probably has several million man-hours of development time in it.  It can be used to design and develop construction drawings for anything -- from a new Hoover Dam, to a kitchen cabinet, to a space shuttle.

 

If you haven't taken any classes in using AutoCAD or drafting, it would be a good idea.  At least it will help a little bit with the headaches - (although i still get them after 25 years of this)

Message 12 of 22
Ron-C
in reply to: GPSJane

You've done sonething I can not determine. There are other lines under your ploylines

I've recreated your drawing and all offset commands now work.

 

 

Message 13 of 22
dmfrazier
in reply to: GPSJane

I did get your attached dwg, and though I was not able to offset it, I had no trouble listing or otherwise selecting the object.

The problem ("Cannot offset that object.") is not unheard of, but I did not find a solution other than to recreate the geometry.

When I exploded the polyline, I did not find any "other lines under" it, but I did notice that one of the inside corners at the upper-right had three unnecessary line segments, one of which partially overlapped another.  One wouldn't think this could effectively disable the object, but...

There may have been something else going on, too, but at this point it may not be worth any more effort (unless it happens again).

Message 14 of 22
GPSJane
in reply to: jggerth1

I know but **** it makes me want to cry.

I don't think I will be able to go on a course but I am considering an online course.
Message 15 of 22
GPSJane
in reply to: Ron-C

Thanks you very much for taking the time to help. I managed to get it working by undoing until it started to select again. I see what you mean - I need to be careful when changing the length of lines and joining them up I think! That corner was changed a few times.

I do struggle with my lines jumping to other endpoints so my lines do get messy.

Thank you so much.
Message 16 of 22
GPSJane
in reply to: dmfrazier

Thank you too. As I say I see what you mean. I think that was the reason for the offset problem as I can now do it.
Message 17 of 22
GPSJane
in reply to: GPSJane

Please can you answer one more question? Can I join these 2 non-touching polylines to make one shape? Like a doughnut.

Message 18 of 22
nestly2
in reply to: GPSJane

Regarding the original issue, BPOLY command is a fast/simple way to recreate the polygon outline that should clean up any oddities with the polyline/polygon

 

I'm not sure about your last question, can you be more specific or add a screencap or drawing?  EXTEND and/or TRIM may be helpful, and FILLET as well, particurally if you're using AutoCAD2014 as FILLET can now be used to close an open Polyline/polygon.

Message 19 of 22
GPSJane
in reply to: nestly2

Thanks I will remember that.

 

Here is the same out line with an offset. I saw a tutorial on extruding 3D shapes from 2D ones. I would like to try it once I'm done. As far as I can see the shape must be closed and flat and this is technically 2 separate lines, not a 2D shape.

 

exterior.png

Message 20 of 22
nestly2
in reply to: GPSJane

If they are closed, you can EXTRUDE them as solids or surfaces.  If they're not closed, they will EXTRUDE as surfaces.  However if you are planning to form "walls" consider PRESSPULL, which will create a region between the two and automatically extrude it.

 

PressPull.gif

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