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Stuck on root node when running behavior tree.

Here's a screenshot of what I mean: alt text

The root node of the behavior tree is the only one running. Is there a specific reason for this? This same behavior tree sequence worked in 4.6, so I'm wondering if anything changed in 4.7 to have caused it...

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asked Mar 13 '15 at 09:58 PM in Blueprint Scripting

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avatar image najir Jul 14 '15 at 08:33 PM

I have the same issue, no idea whats causing it. Followed the AI tutorial on the unreal docs to get some basic ai in and it wont run just stay at the Root node.

avatar image MieszkoZ STAFF Jul 15 '15 at 09:51 AM

The reason for this behavior is behavior tree component not being able to find a task it can run. Try adding a "fallback" wait task and you'll notice that one gets run. I suggest using visual logger for debugging this issue.

avatar image najir Jul 15 '15 at 11:14 PM

Alright thanks for the help :P

avatar image Mattison May 11 '16 at 03:28 AM

Hey! I'm having this same issue, but I'm just trying to get my AI Character to follow me. I did the vislog thing and Found some things that were questionable but don't know how to fix them...

Any help would be greatly appreciated!!!

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4 answers: sort voted first

Ran into this problem myself in version 4.16.1, I'm finally learning how to pop some AI into my concept project and opted to start with the basic tutorial. This was one of the few posts I found where someone ran into the same problem I did, though it seems like it was kind of left without any resolutions. Here's what I figured out for my situation:

  • Set the "Get All Actors of Class" node to have the same class as the object using the AI (since this will be used in the Actors to Ignore pin for the Multisphere Trace).

  • Make sure the multisphere trace radius is set to a value greater than 0.0 (I didn't spot that it was set to 1500.0 in the node picture, so my AI was scanning a radius of nothing).

  • The "Line Trace by Channel" node must have the trace channel as "Camera" rather than "Visibility" or else the object that it's checking for just comes back as "None."

Using the Visual Logger, breakpoints, and also just setting variables to output their values to the log during play helped me stumble through this one, so those are my recommendations for anyone who has different problems getting that tutorial up and running.

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answered Jun 06 '17 at 06:25 PM

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avatar image LocoTaco6 May 22 '18 at 07:57 AM

Thx for saving me hours of searching for the problem. I looked over the "Camera" rather than "Visibility" part so that was my problem.

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The only thing that crosses my mind is that all the tasks fail and BT is unable to "stay" in any task. I've also noticed that one of your "leaf" selectors doesn't have any child tasks - I wonder if that's messing up the BT code.. Regardless, could you record a vis log and send it our way (or investigate it on your own - who knows, you might find something interesting! :))

(to summon vislog UI just run console command vislog, or look around in the menus - I think it's somewhere there :D)



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answered Mar 16 '15 at 02:42 PM

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MieszkoZ STAFF
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My problem was in the AgroCheck blueprint that i copied from the tutorial, the Get All Actors of Class node had no class set :p

Hope this helps someone!

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answered May 16 '16 at 07:54 PM

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So I thought I would let people know what the solution was that I found. It was incredibly easy to miss and i rewent through the entire thing twice.

After hours of going through and break pointing everything. The output log was giving warning, invalid object type. I found out my DesiredObjectTypes in the agrocheck wasn't set. I didn't see this little bit in the instructions, but there needs to be a variable added to that of type pawn. I compiled it, and the ai ran at me and scared me. Hope this helps anyone struggling like I did.

[1]: /storage/temp/270227-ue4aicapture.png

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answered Mar 04 '19 at 08:09 AM

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