Unwanted Hatching Outside Of Polyline

[Jazzy1988]

Hey,

 

I have a hatch (ANSI31) enclosed by a closed polyline. Whenever I change the hatch from ANSI31 to GRAVEL some of the hatch shows up outside the boundary. The Polyline consists of both arcs and line segments, and the hatching errors are occurring within the radius of the arc segments. Changing it from Associative to Non Associative makes no change.

 

I am using AutoCAD 2011.

[MSasu]

Can you post a picture of the trouble maker area?

Since AutoCAD is using line segments to represent arcs, this may be just a visualisation issue (if the hatch doesn’t exceed too much the contour) – a simple REGEN will fix it.

 

Regards,

Mircea

[Jazzy1988]

Can you post a picture of the trouble maker area?

Since AutoCAD is using line segments to represent arcs, this may be just a visualisation issue (if the hatch doesn’t exceed too much the contour) – a simple REGEN will fix it.

 

Regards,

Mircea

 

Please see the attached. I hope this paints a better picture. If the blue hatch is too difficult to see, please let me know and i shall change the colour.

 

I believe it is an error in the hatching.

[MSasu]

Sorry, I cannot see what you are pointing as error - can you modify the colors and/or increase the zoom?

 

By the way, have you tried to do a REGEN?

 

Regards,

Mircea

[Jazzy1988]

I tried regen, and there was no change.

[MSasu]

I see now, thank you. It exceeds more than I was expecting.

Not sure what this can be, so what I will do is: remove the hatch, ensure that the polyline is closed (PEDIT command), perform an AUDIT on drawing and re-do the hatch (may use Inherit Properties to don’t have to set it again).

 

Regards,

Mircea

[CyberAngel]

One remedy may be to redefine the origin of the hatch. The gravel hatch is prone to this kind of thing, I suspect because of its complexity. The further you get away from the origin, the more chance for error.

 

Another remedy, more distasteful, is to break the hatch up into multiple sections. Try to keep the sections more or less rectangular, so the origin is inside the hatch.

 

Edit: You'll notice, where the trouble is occurring, there are segments missing inside the boundary. I'd suspect the origin is at the center of the segments outside the boundary.

[SLW210]

One remedy may be to redefine the origin of the hatch. The gravel hatch is prone to this kind of thing, I suspect because of its complexity. The further you get away from the origin, the more chance for error.

 

Another remedy, more distasteful, is to break the hatch up into multiple sections. Try to keep the sections more or less rectangular, so the origin is inside the hatch.

 

Edit: You'll notice, where the trouble is occurring, there are segments missing inside the boundary. I'd suspect the origin is at the center of the segments outside the boundary.

 

I agree with redefine origin, it seems this has been a problem for a long time.

[Jazzy1988]

Tried breaking the line up into segments, but that didn't seem to help either. I also moved it close to the origin of the drawing, which also didn't work. I believe it has something to do with the lines being exported from 12D (so there are line and arc segments every meter).

 

I redrew the hatch outline as a less complex line (not the most desirable option) and this seems to have fixed the problem.

 

Thanks for all of your help

[irneb]

Could you send a DWG containing the problem hatch & polyline? I've had a similar scenario a few years ago, the reason was that the polyline had some duplicate lines overlapping each other and some endpoints which were on top of each other.

 

Perhaps run OverKill on the polyline to see if this deletes some duplicates, then redo the hatch.

 

Also (though this "shouldn't be a problem) if the PL is an old "heavy-weight" PL you could be running into some inaccuracy problems. Convert it to LW using the Convert command. And to stop using old PL's change the PLineType system variable to the recommended default.

[Jazzy1988]

Please see the attached CAD file.

 

I tried Overkill, no change. And Convert also didn't work.

 

The polylines came from 12D, and they are 2D polylines.

Hatch1.dwg

[irneb]

There seems to be some vectors in that polyline which are simply too close together (some even on top of each other). Playing with Overkill's fuzz gives varying results (even in some cases breaking the polyline into pieces).

 

So it seems it needs a "manual" fix of the PL. Another option is to convert the polyline into a region, and then alternatively exploding it and pedit joining it together again. See attached.

Hatch2.dwg

[Jazzy1988]

Thanks for that!

 

I completely forgot about the region command! As soon as i read it i slapped myself on the forehead.

 

And thanks to everyone else for taking the time to help me with the problem!

[irneb]

Welcome ... strange that region actually fixes this, especially after explode and pljoin. But there you go!