Closed Vs Open Polyline

I can draw a closed polyline representing a closed area.

I can then toggle its 'closed' property and it seems to make no difference. area is same, I can extrude or create regions, I can hatch in either case.

can them somebody explain me as to why, if atall, or in which specific situations we should bother about whether a polyline is closed or not?

If you are drawing a polyline and you use END snap to "close" it (IOW, adding in the final segment), then you do not have a true "closed" polyline. I think you've figured that out.

If you leave out the last segment, and then use "C" inside the command to close it, or use PROPS afterwards to set the Closed property to True - then you have a closed polyline.

In the case of a SQUARE..... The first example above where you manually snap back to the starting point, then close it - that polyline will have 5 vertices. But if you leave out the final segment and use "C" to close it, the square will have the correct 4 vertices.

The difference is mainly noticeable with some programs that read the polyline definition internally to see if it's "closed" or not. Some programs may not work on "open" polylines, even if they appear to be closed.

I wrote up something on this a couple of years ago, you can read it here.

I don't let it worry me. There are more important things in life. LoL

I don't understand what type of response is this. Does it add anything to the discussion? Does it help anybody?

In previous versions of AutoCAD, if the polyline was open, even if its ends were in contact, that entity was rejected by the commands you enumerated above. Now the built-in commands are smart enough to ignore that. But don’t miss that this may not be the case with some third part tools which may reject the entity – if you don’t use such tools, then can leave it in open state with no issues.

Jeez, lighten up dude. It ain't the end of the world.

I deleted my response.

"Some how I am still not convinced as to the significance of this property."

In other words it doesn't matter one way or the other?

I think we just completed the circle.

If you are drawing a polyline and you use END snap to "close" it (IOW, adding in the final segment), then you do not have a true "closed" polyline. I think you've figured that out.

If you leave out the last segment, and then use "C" inside the command to close it, or use PROPS afterwards to set the Closed property to True - then you have a closed polyline.

 

In the case of a SQUARE..... The first example above where you manually snap back to the starting point, then close it - that polyline will have 5 vertices. But if you leave out the final segment and use "C" to close it, the square will have the correct 4 vertices.

 

The difference is mainly noticeable with some programs that read the polyline definition internally to see if it's "closed" or not. Some programs may not work on "open" polylines, even if they appear to be closed.

I wrote up something on this a couple of years ago, you can read it here.

Thanks.

I had already read your post. Some how I am still not convinced as to the significance of this property.

Previously if you wanted to use the EXTRUDE command to create a 3D Solid, you had to start

with a CLOSED polyline. I was just surprised to discover that in 2013 that is no longer the case.

I can draw a closed polyline representing a closed area.

 

I can then toggle its 'closed' property and it seems to make no difference. area is same, I can extrude or create regions, I can hatch in either case.

 

can them somebody explain me as to why, if atall, or in which specific situations we should bother about whether a polyline is closed or not?

(emphasis added) You seem to have answered your own question. The significance of closed vs. open polyline only applies when the area, and thus the polyline, is not closed. As MSasu notes, in olden days you couldn't hatch an open polyline, even if you couldn't see the gap.

Just an observation.

The white square is a closed polyline and the green square is a closed polyline.

Both were hatched.

Both were extruded.

Their areas report back as being the same.

Another observation.

The box is comprised of four separate polylines.

It can be hatched.

It can be extruded yielding what AutoCAD calls a SweptSurface.

Thanks.

 

I had already read your post. Some how I am still not convinced as to the significance of this property.

Then I suppose the answer is "draw them however you want, because there is no difference to you"

But if/when you run across a situation where something doesn't work - at least you'll know what to look for.