Weird behavior when using offset command
Ciel
Traveler
I used the offset tool a bunch a while back for creating city streets that are perfectly parallel, when I first started mapping streets in my city map. At that time, I had no problems. Today, I went to do some more city street mapping using the offset tool in the same way, and sometimes I am getting this weird result:
(click for hi-res)
The highlighted line is what results after using the offset tool and picking the dark gray path right below it as the base entity. See how the newly created line has the two tiny extra lines running off from its end? You can't see it here because I zoomed way in to take this image, but it's identical at the other end of the line with the two tiny lines running off of it. These tiny extra lines continue for an apparently infinite distance: they go off the end of the map and I scrolled out a bunch but didn't see their endpoint.
This behavior occurs when using either "offset one" or "offset copy."
The base entity line is perfectly straight and not especially long, The base entity line itself was created by offset as well, from the line below that one, which was also created by offset from the line below that one (the bottom-most visible gray line was hand-drawn to start this chain of offsetting). But I'm pretty sure I used that technique (making offsets of lines that had themselves been created using offsets of other lines) to create several streets in parallel in my previous work on this map, and I don't recall having this issue.
Oddly, changing the offset distance slightly (e.g. if I want it to be 147 meters, then I change it to 148 instead) will sometimes solve this issue and make the new line render normally, but not always.
(click for hi-res)
The highlighted line is what results after using the offset tool and picking the dark gray path right below it as the base entity. See how the newly created line has the two tiny extra lines running off from its end? You can't see it here because I zoomed way in to take this image, but it's identical at the other end of the line with the two tiny lines running off of it. These tiny extra lines continue for an apparently infinite distance: they go off the end of the map and I scrolled out a bunch but didn't see their endpoint.
This behavior occurs when using either "offset one" or "offset copy."
The base entity line is perfectly straight and not especially long, The base entity line itself was created by offset as well, from the line below that one, which was also created by offset from the line below that one (the bottom-most visible gray line was hand-drawn to start this chain of offsetting). But I'm pretty sure I used that technique (making offsets of lines that had themselves been created using offsets of other lines) to create several streets in parallel in my previous work on this map, and I don't recall having this issue.
Oddly, changing the offset distance slightly (e.g. if I want it to be 147 meters, then I change it to 148 instead) will sometimes solve this issue and make the new line render normally, but not always.
Comments
Edited this post to change from a dropbox link to an attachment; I initially forgot you could just attach files here!
That path of yours have unnecessarily many nodes for a straight line though. You should be able to fix the misbehaving line by running the SIMPLIFY command on it. Just type SIMPLIFY on the command line, hit enter, and then hit enter again to accept the default simplification distance of 10. Now the command line asks you to pick the path, so simply pick the problematic road.
Interesting command. Another one for the list of "commands in CC3 that I didn't know existed until I needed it, and now I'm really glad to know about this". I'll be able to make use of this as I continue to make more streets, I'm sure!
So here's a related question though... sometimes, I've noticed that if I have a line with curves and bends in it, and I use offset, if I put it over a certain distance (say, 150 meters, which is a common length on the long side for blocks in this city, thus when using offset to create parallel streets, "150 meters" is a distance that will come up often), the new line has this starburst mess going on:
Given that this seems to mainly happen with lines that are both curvy/bendy, and are offset by that kind of amount (i.e. even if the line was curvy, if I offset by 50 meters, this doesn't happen), is this just a quirk of how offset works? And thus, that the solution is basically that offset simply isn't a good option for this specific situation?
Simplify on the offset copy should solve this problem.