Dealing with Nodes, Join command and tolerance

[Anonymous]

If you draw two lines (not a P Line), and you want to join them later, why does the join command fail?

If anyone can, I would love for the most in depth complicated answer possible.

Like how is it possible to draw two lines that are on the same plane, with overlapping endpoints.....

close the file...

re-open the file the next day and the lines wont join.

What is going on here?

How does autocad read the inputs and interpret the locations in model space?

If you draw three lines with overlapping end points, how does autocad determine which lines to join?

What is the order in which autocad reads through a command process and where might it be confused given the order in which I run the command?

What is the correct order of operations to ensure that when you draw two lines with overlapping endpoints autocad will understand that these two endpoints occupy the exact same point in space?

Is there a file tolerance setting? Does autocad have multiple c-planes?

Why is autocad seem so inaccurate?

[pendean]

Show your work, post a DWG file with the problem, make sure it opens at the two lines.
otherwise your post is just too generic in nature, and all you will get are generic answers, like JOIJN works just fine over here for us 😉

PS: nothing in a DWG file moves all by itself, that's a user or startup routine trigger. Again, it never happens to anyone else, so you'll need to prove it, which is sadly impossible for anyone not at your computer I suspect.

Oh, this is just a question with no hidden intent: how long have you used AutoCAD for?

[Kent1Cooper]

I assume that by "overlapping" endpoints you mean what I would call "coinciding" [because to me, "overlapping" in relation to Lines sounds like either crossing, or with part of their lengths lapping over each other, in either case meaning their endpoints don't coincide].

I agree that a small posted drawing might help.  Here's a "dumb" possible cause, just in case....  Could they be on a locked Layer?  It is possible for the current Layer to be locked, however unlikely that one would do that intentionally, so you can draw things that right off the bat you can't do anything with.

On the order of objects question, I believe that [and a quick trial worked this way] if you draw 3 Lines with a shared endpoint, if you use Join and select all three, the two that are joined are the two most recently drawn.  Likewise, if you go to pick something where there are multiple things, and you get that little more-than-one-thing symbol, when you pick, and the list of things to choose from comes up, they are listed in drawing order, most recent at the top.

[Anonymous]

No hidden intent, lol, I just really want understand how autocad performs the task so I draw it the way it needs to be drawn. I've used autocad for about 7 years now and the specific issue (while the trigger), is not exactly what I'm hoping to resolve.... I can redrew the lines, move the end points around until they do join or just draw a new PLine..... so I don't think this is a software error, more like user error (but one where autocad would prefer I drew it a certain way to work every time). 

Sometimes lines join sometimes they don't.

In rhino for example if you draw two lines and they don't join the only reason they didn't is because the vertices didn't actually overlap. This could be for a lot reasons ranging from snaps being turned off to bad geometry..... software to user.... point is, its all about how you drew it so rhino knows what to join.

In autocad you can draw a line, do a bunch of other stuff then come back and draw another line starting at an end point of the previous line and then try to join, and it won't work.

I assume that the end points are not actually overlapping, even at such a small scale it doesn't always show up when you zoom in as far as possible.... but this would mean that snap settings are not accurate enough to "snap"?

Anyway file attached.   

[Anonymous]

Yes, I thought the same, layers locked, didn't like joining lines from different layers, one snap setting overriding another (for example if both intersection and nearest is on, then it seems to take the nearest over the intersection unless you get close to an intersection).

Also thank you for the recently drawn info.... so its like illustrator in that autocad is reading the lines drawn on top of each other in the layering of objects like layers in an illustrator file.... or photoshop)..... like thats important to know.

[Anonymous]

for some other reason unknown to me, simply copying these lines into a new file I am now able to zoom in much closer and the end points are clearly not on top of each other and so of course would not join...

so now I'm back to being confused as to how you can draw a line and snap to its endpoints when drawing a second line and zoom in and the endpoints look like this? My grid snap is not on? These were drawn with snaps on and a mixture of ortho being on or off over time and definitely not consecutively... 

[Kent1Cooper]

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@Anonymous wrote:

.... if both intersection and nearest is on, then it seems to take the nearest over the intersection .....

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That's a red flag to me.  It doesn't "seem to" -- it does!  Don't ever have NEArest as one of your running Osnap modes!  It will almost always "win out" over all others, because the nearest point to the cursor location on any object that crosses the Osnap aperture will, by definition, almost always be closer than any other Osnappable location(s) on it, so that's what it will snap to.  [There are specific circumstances where it may not be, some of which I could describe if you want, but they're rare.]  If you really want NEArest in favor of any of the others in some situation, call for it explicitly at the time, but don't have it running all the time.  If you've been drawing with it on, that could well explain your Joining problems.

[leeminardi]

"Overlapping" lines will not be joined.  The ends must be coincident.  

Here's one problem in your drawing.

Use chamfer with a values of 0.0 to clean up these corners.