topic Re: Clipped Viewport Causing thick lines where Polylines cross it. in Civil 3D Forum

Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Mon, 20 Oct 2025 18:18:47 GMT

Clipped Viewport Causing thick lines where Polylines cross it.

The lines only appear thicker when printed, and appear in multiple pdf viewers

Things I've tried:

Viewport Clip polyline - global width of 0

Frame set to 2

attempted to change the plot to "DWG to PDF.pc3"

changed the object lineweights to 0 (using ctb)

changed linetype settings, and a bunch of other recommended fixes from Gemini AI

Removing the clip, and using wipeouts appears to fix the problem, however there are scenarios that require clip in our template. So I need this fixed.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

RobertEVs — Mon, 20 Oct 2025 20:11:44 GMT

I'm not connecting your png to what you are referring to in your post. Is the edge of road edges the thick ones not wanted?

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Mon, 20 Oct 2025 20:14:01 GMT

where the polyline approaches and crosses the viewport, the polyline is extra thick.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

ChrisRS — Mon, 20 Oct 2025 21:27:28 GMT

Troubleshooting ideas:

Is this specific to one drawing? Try recovering the drawing.
DO you have the same problem on multiple computers?
If you have core AutoCAD available, try printing from there. Does the problem persist?
What type of object is it? Do AutoCAD and Civil 3D objects work differently?

A sample drawing would help us troubleshoot.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Mon, 20 Oct 2025 21:36:35 GMT

Unfortunately, it's been happening on multiple computers, programs, templates and for a few of our techs. This occurrence was actually an AutoCAD LT drawing, which was also doing it to me in my 2026 Civil3D install as well.

I'm the local "fix it" tech and was asked to help the designer with these lines on their record drawing, which was not doing this in May when printed for Construction. I've noticed this happening with a few other techs and versions of AutoCAD and C3D in our company.

I found something in my internet digging about clipped viewports causing this issue. When I removed the clip boundary on the viewports, the issue resolved. Attached is the drawing, different page; but was giving the same issues.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Mon, 20 Oct 2025 21:58:12 GMT

Some additional information; the problem drawing was drawn completely in 2D, and giving thick contours, and other linework as well at the clipped viewport, but Civil3D was only making the road edge lines thicker. so inconsistency in the same issue when printing to PDF.

plotted from AutoCAD LT: (Above snips were plotted from 2026 Civil 3D)

Re: Clipped Viewport Causing thick lines where Polylines cross it.

na_divercity — Thu, 30 Oct 2025 10:23:38 GMT

To add another voice... I'm having the exact same issue, this seems to be happening with AutoCAD LT 2026, colleagues on AutoCAD LT 2025 do not experience this issue. So maybe this issue affects the PDF export facility across multiple products?

Image A shows that the cropped lines print with a thicker line when cropped by the viewport
Image B shows that the uncropped lines print correctly in PDF when NOT cropped by the viewport

Curiously, this thicker line effect will also happen to lines that are very very close to the viewport edge even if they do not actually crop.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Thu, 30 Oct 2025 15:14:00 GMT

That's exactly the issue we are having and after some additional conversations, it appears only 2026 is causing the issue here as well. Any line/polylines that cross or approach the clipping line are being affected, but it's inconsistent which ones from user to user / computer to computer.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

dkennedy — Thu, 30 Oct 2025 16:03:06 GMT

Maybe the viewport is corrupt?

Have you saved the layer state for the viewport, then recreated the viewport?

Re: Clipped Viewport Causing thick lines where Polylines cross it.

tcorey — Thu, 30 Oct 2025 16:26:39 GMT

I don't understand what your exact issue is. Can you post that previous image with some notation? Which is the clipped viewport, which are the lines being thickened?

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Thu, 30 Oct 2025 16:53:36 GMT

Tried this a few times, on multiple projects.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

jbaxerGA33V — Thu, 30 Oct 2025 16:55:46 GMT

Lines are extra thick where they cross or approach clipped viewports, or object clipping boundaries. it's random, and inconsistent. only consistency is the clipping, and 2026 installations of autodesk / AutoCAD based programs like Civil3D, and AutoCAD LT.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

billhynsonQ59TQ — Thu, 06 Nov 2025 15:40:30 GMT

We are having this same issue as described above. Our company is halfway through updating people from Civil3D 2023 to Civil3D 2026.

Again, this problem only arises with clipped viewports. If you look at my attached photo, you'll see an example of one viewport (not clipped) versus a clipped viewport of the same area.

If you look along the left edge of the pictures, you'll see that lines and text are affected. It seems to only affect contiguous lines, so if there is a gap in the linetype, then only the portion that crosses the edge of the viewport is bolded.

We have had our users on the 2023 version open the exact same file and print it and it looks fine/as it should, so we've narrowed this issue down to what we expect is a 2026 issue. Windows 11 vs Windows 10 users experience the same issue. Print preview appears to look normal, but when you actually print to PDF, as well as printing to physical copy, the bolding issue persistent.
I have also attached the drawing so if you see any solutions or have any troubleshooting suggestions please share and I'll give them a try.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

lauri_barnhart — Mon, 10 Nov 2025 20:22:42 GMT

Hi @billhynsonQ59TQ,

I wanted to check in and see if you still needed assistance, or if you found a solution to your question already? Let us know if you need further assistance by providing an update or if you have found a solution, please share it with the community so other members who may have the same question could learn from your experience.

All the best,

Lauri | Community Manager

Re: Clipped Viewport Causing thick lines where Polylines cross it.

billhynsonQ59TQ — Wed, 12 Nov 2025 00:18:04 GMT

@lauri_barnhart

Hello Lauri,

Unfortunately, we have not found a solution to this issue yet. I've continued to try searching for a solution but have had no luck. I do feel like this is a 2026 version specific problem, as all of our other version users do not have the issue when they open the exact same drawing on the older versions.

Until we figure out a solution I've just stopped upgrading versions for our company.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

Ash_Christensen — Wed, 12 Nov 2025 07:05:35 GMT

I'm so glad I've found someone else having the same issue because I was starting to go mad!

I've been having this problem for months, and only put together today that it was related to the viewports. This issue is across multiple different drawings, in different projects, started at completely different times (one drawing was started in 2023, the other only last month). I don't even want to think about how long I spent checking xrefs for hidden lines while trying to sort this out.......

I am using ACAD LT 2026, and I know this wasn't a problem in 2025 because I have printed these same plans previously with no issues.

Are there any plans to fix this from AutoDesk or should I go back to 2025?

Re: Clipped Viewport Causing thick lines where Polylines cross it.

cwitzel5NL5H — Thu, 13 Nov 2025 15:24:04 GMT

This is a known defect. Please report your instance as well. Maybe we will get some more traction. We are holding off on moving to 2026 until this is fixed.

Re: Clipped Viewport Causing thick lines where Polylines cross it.

CGBenner — Tue, 25 Nov 2025 11:24:22 GMT

@cwitzel5NL5H

"Please report your instance as well."

Hi, Conan. Have you opened a Support case to report this to someone at Autodesk? If so, can you share your case # so we can follow up on it? Thank you!

Re: Clipped Viewport Causing thick lines where Polylines cross it.

cwitzel5NL5H — Tue, 25 Nov 2025 16:23:03 GMT

I have it as Defect CPR-739 submitted on 10/17/25.

Thanks,

Re: Clipped Viewport Causing thick lines where Polylines cross it.

Ash_Christensen — Tue, 25 Nov 2025 22:17:43 GMT

I have also reported this, Issue ID CPR-837, 20/11/25, initially Support Case 25037952.

Cheers,

Ash