Unreal Engine 5 Tutorial - AI Part 4: Decorators

In Part 4 we look at how decorators work in a behaviour tree and how we can create our own if we need to.
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[@revan9903]

For anyone having problems with weird behaviour with the custom decorator, the scale comparison doesn't work as intended. The actual vector length of the scale with standard scale settings (1,1,1) is 1.732051. So the old behaviour won't trigger if you don't set the acceptable scale value higher. Also because the Target actor is still set, the NPC Character won't go to random locations when he sees you. Also you get some random behaviour which siwtches between doing nothing and weird running around. I haven't found out the reason for the last one.

[@DSJ11]

Hi Ryan, I'm a technical designer at Tt Games and this series is helping me out during our annual game jam, so thank you!

[@MulliganMTG]

My daughter loves Lego Harry Potter. That was you guys right?

[@DSJ11]

@@MulliganMTG It was! (Before I joined the company) Really glad to hear your daughter enjoys it :)

[@Empirax]

You hiring ?

[@brodiemorris2081]

your company made my (and my brothers) childhood. Thank you for that.

[@davids2551]

Two minutes in and this video has already helped me more than a 2 hour tutorial with my lecturer If you set a Blackboard query to use an integer or float as its key, the key query will change to check isequal/greater/lessthan. KeyQueries change based on the type of KeyValue. So crucial. Didn't know this feature existed.

[@boolean711]

Thanks for taking the time to explain the decorators, this series has so far been the best behavior tree one yet!

[@morndulin]

Thank you SO much for this tutorial and explaining decorators.

[@polite-cat]

Thanks for this great tutorial. I made dialog options select based on decorators

[@epsiloncore9772]

I'm sure I followed your tutorial accurately but for some reason I can't tell if iit's working the AI will have moments where it will see my player character and just stand there for a good few seconds before running. about.

[@javisartdesign]

Thanks really awesome tutorial

[@dustinherrick8472]

I've been following your full tutorial here and something's goes wrong on part 4. Before I added check scale decorator the AI would give Chase as with part three of your tutorial even with the player character at 1.0 the AI no longer chases and anything greater than 1.1 I get the same result the AI just walks around and sometimes. In place and do nothing. I noticed you also added the video where you don't show where you interact before you change the size of your character and it just go straight into your character being greater than 1.1. I'm not sure if you cut something out or I'm missing something I am new to this but this did not work. I'm going to take this step out and go on to the next part of the tutorial. This is my second time going through your tutorial as the first time I went through everything worked up until part 4, I continued anyways onto the sound on part 5 and part 6 and nothing was working after part 4

[@bengwynne6823]

Your videos are great but this doesn't work for me - am I also the only one who missed completely when you made the BP_ThirdPersonCharacter larger than 1.0?

[@RtxRob]

Hey Ryan, Thanks for tutorial, could you please add this video to your playlist "Unreal Engine 5 AI". Thanks

[@unreal_metronomus678]

Hey Ryan, could you please show how to create an ai director that shares EQS data between the ai bots. For example I would like to send my enemies to eqs positions, attack formations. I have got something like that working, but I don’t like the way I coded it. Perhaps there is a better way.

[@RyanMcEachern-mr7jc]

not quite sure if anyone else will have this problem of the AI not following you but, if the ai will not follow you. when you make your max acceptable distance make the value 100 and not 1.1 the A.I Will follow you now.

[@jmartian6426]

I watched the float for the actor scale and apparently, it returns 1,73 even though my character's scale is just (1,1,1). Setting the actor scale to 1,1 for each axis, will return a float of 1,90.

[@rifat.ahammed]

Great

[@aProperFox]

Just in case someone tries to compare and gets confused, at 6:48, you say "if your size is 2, 2, 2, your value will be 2." which is inaccurate. The value is calculated as the square root of the sum of squares. So while 1, 1, 1, equates to 1; 2, 2, 2 equates to: sqrt(2^2 + 2^2 + 2^2) = sqrt(12) = 3.464.

[@FPChris]

1 1 1 length is returning 1.732051

[@carlosrivadulla8903]

Pls give it a try to the state tree

[@djtc2093]

Could you point me in the direction of how to add AI shooting logic to the behaviour tree.

[@FPChris]

After fighting with the results of this video for an hour I've decided to move on. I could only set Quinn to 2,2,2 scale by directly calling Set Actor 3D Scale. Setting the scale of the Player Start, BP_ThirdPerson, or even the Quinn's Skeletal mesh inside to 2,2,2 still returns an Actor Scale 3D of 1 1 1 in the Decorator. Extremely confusing.

[@unrealdevop]

I'm not finding Blackboard Based Condition....Do people just not use Behavior trees for Ai or something? It seems insanely difficult to find even the most basic stuff on this, like simply resetting the value of a Blackboard key from the Behavior Tree and simple If conditions. I should mention that I looked for an example of a custom Decorator and found absolutely no examples....which is really odd.

[@ThatSupportTho]

whats a scale 3d?

[@overlandgames]

quick newbie question, and maybe i just missed something easy, but the blackboard key "Target" at the end of the tutorial here, where does that come from? How does it know to grab the actual target actor? in the previous tutorials, i just have blackboard keys "TargetActor" "SelfActor" "TargetLocation" "LastKnownLocation". the blackboard has at least two object keys that are actors (Self and TargetActor) so in the self made decorator, when you make a variable that is a blackboard key called 'target' i don't see where that actually references the blackboard key "TargetActor." only , get value as object? How does the decorator know you're referencing the target actor?

[@leonelsandoval987]

I have the same problem. I can not find the point where the "Target" is connected to "BP_ThirdPersonCharacter" or whatever actor I want. Unsolved yet.

[@ConspiracyCraftersStudio]

same problem here, have you solved it? its hard to follow sometimes@@leonelsandoval987

[@NikEki-1337]

It is from the previous episode. TargetActor is being setset in HandleSightSense function in AI Controller BP.

[@Ataxire]

Not sure why but when the ai loses seight of me it starts having a seizure and doesnt know where the go next so it just snaps back and forth trying to walk somewhere

[@brandonstam626]

An issue I'm having: If my character is less than Max Acceptable Scale, the AI will just completely stop once it sees me. If my character is greater, the AI will keep trying to go to my location. My understanding is because it's trying to go to MoveTo:Target Actor or MoveTo: LastKnownLocation. I have the same set up as the video, but it seems the AI in the video pis able to jump back to BTTask_MoveRandomLocation. How is that?

[@TheBradinator64]

Hey, don't know if it's caused by the same issue I had, but my issue came from the Get Vector Length node in the custom decorator not working as intended. Instead of using that to compare to the max acceptable scale, I had to split it into its x, y, and z components and compare each of them individually to the max acceptable scale. I then also had to add another random movement node to the right of the Chase Selector node in the behaviour tree. Hope this helps :)

[@gail_blue]

It's a great tutorial, but the scale thing doesn't work for several reasons: (A) You're testing the scale of the actor, not it's mesh component, so regardless of what you scale the mesh to, it will always be [1,1,1] (B) The vector length of [1,1,1] is 1.73 and the root component of an actor doesn't really have a scale, so this decorator is essentially useless. That said, it's arbitrary, so it doesn't really matter if it works or not. What's important are the methods behind it, which are solid. I'm finding this series useful because it stays on point.

[@jhow8894]

The unreal's AI system is HORRIBLE (I've never done anything with AI before) my brain is spinning

[@FPChris]

Agreed. There NUMEROUS different systems you are suppose to figure out how to marry up.