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CrowdManager never calls StartUsingCustomLink() on Agents when Custom NavLinks are placed in the level and traversed.

I came across this bug while trying to figure out the issue in this question HERE.

The basic issue is StartUsingCustomLink() never gets called in the CrowdManager when an AI with a UCrowdFollowingComponent begins to traverse a NavLinkProxy that has been placed in the world.

As mentioned in the answer of the other question, the link UserID always returns 0, so it believes that we never traverse a valid Custom link. The actual custom link ID seems to be offset by 1 in the navmesh tile link data.

However this ONLY works with pre-placed CustomNavLinks.

Once I attempt to spawn them dynamically the NavMesh does NOT contain the user ID's even if I dirty the area containing the NavLink causing it to recalculate the NavMesh.

As an example; in a tile queried there are 2 CustomNavLinks one pre-placed, the other created at runtime. When requesting the LinkUserID the tile has the following links:

 LogTemp: Index Requested: 0
 LogTemp: Connection: 0 LinkID: 0
 LogTemp: Connection: 1 LinkID: 53
 LogTemp: Connection: 2 LinkID: 0

53 is the ID of the pre-placed NavLink, however it requests the link at index 0 when attempting to traverse it. (Which is wrong) and the connection at Index 2 is the one dynamically placed.

I've attached a sample code project built with the launcher 4.15 of the engine demoing the issue HERE. This issue is present in 4.13 as well as that is the version I originally saw this issue in.

I have yet to find a work-around which actually works in all cases, and would appreciate it if one could (hopefully) be found.


Product Version: UE 4.15
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asked Feb 23 '17 at 08:58 AM in Bug Reports

FacePalm.exe gravatar image

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Sean Flint gravatar image Sean Flint ♦♦ STAFF Mar 03 '17 at 04:16 PM

Hey FacePalm.exe,

I'm looking into the issue, and I'll respond as soon as I have new information. I apologize for the delay.

FacePalm.exe gravatar image FacePalm.exe 6 days ago

Hi Sean,

Is there any update to this at all, or is it still being looked into?

Sean Flint gravatar image Sean Flint ♦♦ STAFF 6 days ago

I've reached out to one of our developers for some additional information, but I haven't heard back just yet. I'll let you know as soon as I do.

Thanks for your patience

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1 answer: sort voted first

I've gotten a ticket in for this issue based on one of our developer's request:


Thank you for your report and for your patience.

Have a great day

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answered Mar 20 '17 at 08:29 PM

Sean Flint gravatar image

Sean Flint ♦♦ STAFF
39.3k 424 106 360

FacePalm.exe gravatar image FacePalm.exe 2 days ago

Cheers for the update. :)

Sergey.Nt gravatar image Sergey.Nt yesterday

Hi FacePalm.exe,

You have mentioned a workaround for the issue. Could you please share one? I have similar issue: when FPImplRecastNavMesh::FindStraightPath is called it adds custom links with userId == 0. And that prevents StartUsingCustomLink() from being called. (using 4.15).


FacePalm.exe gravatar image FacePalm.exe yesterday

The work around I mentioned is more of a hack. You can find it HERE.

I don't know if FindStraightPath() uses dtNavMesh::getOffMeshConnectionByRef(), but wherever it fetches the UserID you can probably do something similar.

As I mention in this question you CAN NOT add links at runtime otherwise this work-around doesn't work.

Hope that helps. :)

Sergey.Nt gravatar image Sergey.Nt yesterday

Thank you for sharing that.

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