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Impassable lines on the nav mesh preventing AI from crossing cells

The Nav Mesh Bounds volume in one of my levels is acting up, displaying green lines over the nav mesh which cannot be crossed by AI characters.

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Changing some of the settings in the RecastNavMesh settings to change the cell sizes and things will move the location and the amount of green lines (it appears to be the line separating each cell) but I cant get them not to be there, feels like a bug.

The terrain in the image is at a world location of (X=179916.000000,Y=-9594.000000,Z=40.000000) and it seems to be something in this area of the world causing the problem. If I move the terrain and the nav mesh closer to 0,0,0 the lines don't appear and everything works as expected.

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Using the nav testers you can see the paths just wont cross over the green lines, preventing AI from working correctly.

I can fix the issue using a Nav Link Proxy which allows paths over the green lines, but this isn't ideal in context of the level layout.

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I have tried multiple solutions to fix and have just been fiddling with the nav size settings and scan options (switching from static to dynamic etc) but I am only stabbing in the dark really.

Anyone aware of the cause of the issue or any advice to solve this?



We tried creating a Nav Mesh and terrain in the exact same world location on a vanilla copy of UE4 not using our custom code and everything seemed to work fine.

Perhaps the issue is being caused by elements of our code base, unsure where to start debugging this however.

Product Version: UE 4.8
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asked Jun 12 '15 at 11:36 AM in Bug Reports

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avatar image Adam Davis STAFF Jun 12 '15 at 06:11 PM

Hi CptWallace,

This looks like a landscape, can you try using the sculpt tool on a small amount of the landscape to see if this error still occurs? If it is not a landscape, what settings are you using in the navigation portion of the project settings?

avatar image CptWallace Jun 15 '15 at 11:39 AM


The nav mesh from the image is on a landscape correct, I have tried building paths on static mesh, landscape and BSP surfaces always with the same issue.

The settings of my nav are all default but I changed the build to dynamic instead of static, although either doesn't fix the problem.

avatar image Adam Davis STAFF Jun 15 '15 at 03:38 PM

Hi CptWallace,

Can you send me a sample project that is displaying this? I'll be happy to take a look!

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Hi CptWallace,

We haven't heard from you in several days. I am marking this thread as answered for tracking purposes. If you are still experiencing this error, please comment with the requested information.

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answered Jun 21 '15 at 07:40 PM

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