Unnecessary Fillets when using FILLET on Polyline with Arcs

[CColozza]

I'm encountering an odd issue when using the FILLET command on Polylines that contain both lines and arcs. I've got a LISP program that is based around using this FILLET functionality, and I've determined this is the source of my troubles. Perhaps this issue has already been resolved somewhere else, as it's rather hard to explain briefly.

I start with my polyline, which (as shown in the attached images) has a section where it alternates between line-arc-line-arc etc. I OFFSET the polyline without any hiccups. Clearly there are vertices at each of the connections where the arcs and lines join, on both the old and new polylines. After applying the FILLET command to the new polyline, I noticed that I can't OFFSET the new polyline. After clicking on it, places where I thought vertices would be are now midpoint symbols (see red circles in image). After clicking around, I discovered that if I drag on any of what would've been "original" midpoints, 4 new vertices show up, 2 new straight lines form, and the line I'm dragging moves around without deforming (see upper right part of image). It's like the FILLET command is creating fillets of radius infinity and length of zero. What's really going on here, and is there a way for FILLET to stop inserting these zero-length segments between arcs and lines? Can FILLET not handle a polyline with both arcs and straight lines?

[Kent1Cooper]

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@CColozza wrote:

.... I start with my polyline, which ... has a section where it alternates between line-arc-line-arc etc. I OFFSET the polyline .... .... After applying the FILLET command to the new polyline, I noticed that I can't OFFSET the new polyline. After clicking on it, places where I thought vertices would be are now midpoint symbols ....

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Can you post a small drawing file?  With before and after contents.

How are you "applying the FILLET command to the new polyline"?  With the Polyline option in FILLET?  [And why, if it's already got the arc segments from being Offset from one that has them?]

[CColozza]

Unfortunately I can't upload the original drawing, as it contains privileged information. However, when I copied the desired polyline over to a new drawing, the issue changed. In a new drawing with the same polyline just pasted in, the attached image is now what I'm getting; the polyline with red circles is the original, and the red circles now contain what appear to be vertices on top of mid-point line symbols, indicating that the lines are so short they cannot be seem unless I zoom way in. I tried then moving this polyline back to the original drawing in its original location, and it went back to showing only mid-point symbols where vertices should have been.

In the new drawing, I used OFFSET to create a different polyline for demonstration purposes, and then used the FILLET command with POLYLINE selection. Afterwards there weren't any errors but there were still vertices on top of mid-points. I drug the apparent vertices away and I discovered there were several imperceptibly short lines in both the original polyline and the OFFSET polyline (see jagged shapes in image).

Upon returning to the original drawing, I would have to imagine that there are extremely tiny lines/fillets that are present for some reason, but are too small for AutoCAD to draw properly, hence the several mid-point symbols. I decided to re-draw the polyline, and that solved all of my problems. The unanswered question is how those odd lines got there in the first place. Is there any way AutoCAD can remove all lines and arcs smaller than "X" length from a polyline?

[Kent1Cooper]

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@CColozza wrote:

..... Is there any way AutoCAD can remove all lines and arcs smaller than "X" length from a polyline?

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If they are tiny line segments and collinear with adjacent line segments, >PLDIET.lsp< should remove them.

[CColozza]

OK, for further investigation, I tried using your PLDiet.LSP routine on the original polyline. I used OFFSET, ran the FILLET command with POLYLINE, and then proceeded to use PLDiet on the new polyline. I chose a max distance of 20, a max change in direction of 330 degrees just to be safe, and asked it to (S)traighten all arcs. Attached is what I get in return; still a bunch of extra mid point symbols where there should be vertices. For reference, the separate line drawn is 20 units long, more than enough to cover any lines that are too small to see. There shouldn't be any arcs on the polyline anymore, since I asked PLDiet to straighten them all. The original polyline is LW and should have tangent relationships between arcs and lines. Do you have any other ideas I can try?

[Kent1Cooper]

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@CColozza wrote:

Unfortunately I can't upload the original drawing, as it contains privileged information. .... Is there any way AutoCAD can remove all lines and arcs smaller than "X" length from a polyline?

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Can you post a drawing with just one or two of those Polylines in it?

If there are no widths involved, you should be able to EXPLODE the Polyline, use QSELECT or FILTER to find Lines/Arcs of zero length [or shorter than some small length you specify], ERASE those, and PEDIT/Join the other pieces back together [with a fuzz factor if necessary].

[CColozza]

I believe I understand where you're headed with this; I'd have to break everything apart and reassemble the polyline. I've attached a drawing with just the improperly functioning polyline for your inspection. Just running FILLET with the POLYLINE selection creates the original problem I posted about, where midpoints are showing up where I'd expect vertices to be.

[Kent1Cooper]

It seems [in very limited trial] to happen only at the ends of already-existing arc segments when Fillet's Polyline option is applied.  And they're not zero-length, though very short.  That suggests to me that maybe the existing arc segments are not precisely tangent to the line segments they meet at those places, but I'm grabbing at straws....

[CColozza]

I've been trying to get the original file with the polyline to work, and nothing I do seems to improve the issue. It all comes down to applying the FILLET command to a polyline with arcs AND lines. It seems the command creates these super tiny lines (not fillets) between arcs and lines, and since they are so small, AutoCAD only sees the midpoint for some reason(?). PLDiet did not work to clear any of the lines up. I decided I wasted enough time trying to fix this, and just redrew a new polyline that was similar enough. Not really a working solution but one that was the most time-conscientious.

[Kent1Cooper]

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@CColozza wrote:

.... It seems the command creates these super tiny lines (not fillets) between arcs and lines.....

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At least some of them are arc segments, not line segments, or it wouldn't offer to convert them to Line segments when hovering over their midpoints [here Zoomed way in]:

Not that I have any ideas....  Something else funny is going on, because that tiny arc segment resulted from my applying the Polyline option in FILLET with a radius of 30 [the default in the drawing], but the radius of that one is 30.0044.