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Nav Link Proxy SmartLink functionality doesn't work

In 4.8 previews 3 and 4 NavLinkProxy objects' SmartLink properties don't work. Neither the link nor the box obstacle are created when placed and Smart Link Is Relevant checked. Breakpoints in UNavLinkCustomComponent::GetNavigationData() are never hit, though the component does register and unregister. The NavLinkProxy's simple links all appear to behave correctly, though, and NavModifier volumes also work

Product Version: UE 4.8 Preview
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asked May 28 '15 at 06:44 PM in Bug Reports

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avatar image Adam Davis STAFF Jun 01 '15 at 07:24 PM

Hi TheNoonicorn,

Can you show me a screenshot or video of what you are seeing on my end. We have several users reporting errors with nav links and I'd like to see if the issues are the same.

avatar image TheNoonicorn Jun 01 '15 at 08:27 PM

Here's the nav link with simple links and smart link turned on

alt text

Here's the same link with the simple links deleted

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Here's a quick video of me messing around with the settings, switching stuff on and off, with only the SimpleLinks actually having any kind of effect


In all of these the nav link smart link arrow isn't visible, and no nav obstacle is created. Internally in code in order to get these to show up I added checks for smart links in the following functions:

 bool ANavLinkProxy::IsNavigationRelevant() const
     return (PointLinks.Num() > 0) || (SegmentLinks.Num() > 0) || bSmartLinkIsRelevant;  //Relevant if smart link is relevant
 void ANavLinkProxy::GetNavigationData(FNavigationRelevantData& Data) const
     NavigationHelper::ProcessNavLinkAndAppend(&Data.Modifiers, this, PointLinks);
     NavigationHelper::ProcessNavLinkSegmentAndAppend(&Data.Modifiers, this, SegmentLinks);
     if (SmartLinkComp && bSmartLinkIsRelevant)
         SmartLinkComp->GetNavigationData(Data);  //Update nav with obstructions and smart links

I also updated the PostEditChangeProperty function as follows:

     if (CategoryName == TEXT("SimpleLink") || MemberCategoryName == TEXT("SimpleLink") || bSmartLinkIsRelevant)
         UNavigationSystem* NavSys = UNavigationSystem::GetCurrent(GetWorld());
         if (NavSys)

With those updates the links work, but I don't remember having to do that in 4.7

avatar image Adam Davis STAFF Jun 01 '15 at 08:34 PM

Does this occur in a blank project with no additional content?

avatar image TheNoonicorn Jun 01 '15 at 08:43 PM

Yep, same issues. Attached an empty project from 4.8 launched from the EpicGamesLauncher rather than from VS debugger

link text

edit: to clarify above, the code edits I did were not present when I took the screenshots and video. With the code edits the nav link proxy behaves like it does in 4.7

avatar image Adam Davis STAFF Jun 03 '15 at 07:44 PM

Unfortunately I haven't been able to reproduce the effects of your video on my end. Do you have any other steps I can take to reproduce this on my end?

avatar image TheNoonicorn Jun 03 '15 at 11:22 PM

I don't have any other repro steps apart from run the Epic Games Launcher, choose 4.8.0 preview 4, and create an empty project. Here's a video showing just that, with confirmation that Nav Modifier Volumes work where Nav Link Proxy obstacle volumes do not


avatar image Adam Davis STAFF Jun 09 '15 at 07:03 PM

Hi TheNoonicorn,

I will continue to try to reproduce this, as it clearly is occurring in the video. However I haven't found any reproduction steps on my side that seem to work. What operating system are you using?

avatar image TheNoonicorn Jun 09 '15 at 09:30 PM

We're using Windows 8.1 Pro here

avatar image Adam Davis STAFF Jun 10 '15 at 08:44 PM

Hi TheNoonicorn,

I haven't been able to reproduce this on my end. Can you list step by step the exact steps you are taking that cause this to occur in the project you posted here?

avatar image TheNoonicorn Jun 10 '15 at 10:49 PM

I can, but I'm just going to be narrating the video. The steps used to produce the project are the same in both. I just got the officially released 4.8.0 version through the launcher, did the exact same things in the video, and the nav link proxy's Smart Link and Box Obstacle still don't work.

1) Get latest release

2) Start new project.

3) Put Nav Mesh Bounds Volume into the world on the platform.

4) Increase nav mesh bounds volume's brush extents to make sure the whole area is covered in nav mesh. Putting 5000 into the X Y and Z fields is a quick and easy way to do this.

5) Hit P to enable nav display.

6) Place a NavLinkProxy into the nav mesh.

7) In the nav mesh link's properties check the Smart Link is Relevant box to enable Smart Link abilities.

8) Become concerned when nothing happens.

9) Wiggle the Nav Link Proxy to attempt to force the nav mesh to rebuild.

10) Become more concerned when the nav rebuilds but there is no change with the Nav Link Proxy.

11) Check the Create Box Obstacle box to create a nav obstacle around the Nav Link Proxy.

12) Repeat steps 8-10.

Following these steps in 4.7.6 diverges at step 7 when the Smart Link's arrows appear, and then when checking the Create Box Obstacle box creates an obstruction area that removes nav mesh around the proxy. Here's a 4.7.6 vs 4.8.0 video showing the same steps in the different versions of the engine, with 4.7.6 working correctly and 4.8.0 not.


Additionally, here's both of the projects created while recording that video

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2 answers: sort voted first

Hi TheNoonicorn,

Ok I see what you are talking about now, I apologize for the previous confusion! This is a known issue and is in our system as UE-16448.

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answered Jun 11 '15 at 03:57 PM

avatar image TheNoonicorn Jun 12 '15 at 01:24 AM

cool, thanks!

avatar image nonder Jun 13 '15 at 05:24 PM

Ported my project to 4.8 and found this bug too. My nav links don't work, so 4.8.0 is unusable for me.

avatar image Robin.UltraUltra Jun 17 '15 at 07:01 AM

Same here, 4.8 makes my project not work as intended because of the smart links not working.

avatar image Adam Davis STAFF Jun 17 '15 at 05:32 PM

Hi everyone,

I've bumped the community interest section of this bug report to better reflect how many developers are currently affected by this.

avatar image nonder Jun 17 '15 at 11:18 PM

I am sure that important (actually, I just hope) bug like this one (I think Mieszko understand how important it is) will be in first or second hotfix. This one is not like "add it to bugtracker, track community interest and maybe we can look on that for 4.9" :)

avatar image Ben Halliday STAFF Jun 18 '15 at 01:04 PM

That's entirely up to the developers. We'll update this post when we see a fix come through.

avatar image Mazy.UltraUltra Aug 25 '15 at 01:57 PM

Hey, are there any updates on a fix for this?

We're really hoping that this will be looked at and fixed soon since it's severely impacting our project in key areas at the moment, and in the case that there's no fix on the horizon then we'll be forced to look at some pretty drastic workarounds and compromises very soon (which we're really hoping won't be the case)

avatar image Adam Davis STAFF Aug 25 '15 at 02:24 PM

Hi Mazy.UltraUltra,

This is still being assessed by the development staff. Unfortunately, I do not have a timeframe of when a fix will be made available.

avatar image Mazy.UltraUltra Aug 26 '15 at 10:23 AM

Aight, thanks for the update.

avatar image FMasse_Panache Nov 12 '15 at 06:55 PM

Any update on this issue? The code fix above doesn't seem to work (anymore?) on 4.9 and I haven't seen a fix for this issue in the 4.10 changelist.

avatar image Adam Davis STAFF Nov 12 '15 at 07:06 PM

Hi Anaxagor14,

This is still under assessment. Unfortunately I don't have a timeframe of when a fix will be made available, nor do I have any other workarounds that you could try at present. I have edited the bug report to show that more developers are experiencing this issue.

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I have a partial fix I've found that may indicate where the deeper problem is. I had the output window up, which I'm totally doing more often now, and noticed I kept getting a message early on when the level loaded up saying "SmartLinkComponent could not be added to octree because parent (PositionComponent) is not in nav octree." My super quick fix was to implement GetNavigationParent() in NavLinkCustomComponent and have it always return nullptr. This forces it to always be added into the nav tree and voila, my links were working again, obstruction areas and all.

One caveat to this fix though is that it only works on cooked builds with nav mesh in different sublevels if Rebuild At Runtime is enabled. This is due to a separate issue that was reported a bit ago. In PIE mode though, or with all nav mesh and links in the main level, it appeared to work all the time. YMMV

Anyway, that's partially fixed that major problem for us, just posting here in case it helps anyone else.

 UObject* UNavLinkCustomComponent::GetNavigationParent() const
     return nullptr;  //Returning null so that we add this component directly into the nav tree
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answered Jun 25 '15 at 12:03 AM

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