Need Some Help To Get a Better Understanding of Behaviour Trees

[AmareshB (Amaresh Beuria)]

Hey Guys! I’m following along with the Behaviour Tree tutorial in the UE4 Documentation https://docs.unrealengine.com/latest/INT/Gameplay/AI/BehaviorTreeQuickStart/index.html

I’m a bit confused with all the decorators used over the sequence node. So, I thought who, better than the community, can explain it better. So I’m posting thread.

Please explain the use os these decorators

And How can I make the AI Character wander around randomly instead of going back to the home location. I’ve created a task (PickRandomLocation) to get the random point inside a given radius. But I’m unable to make it work inside of the behavior tree.

Please Help.
Thank You.

[pattym]

I’ve been playing with behavior trees recently and from what I’ve gathered “decorators” are a fancy way of saying “Gate”. You set conditions inside the decorator that controls whether the flow can continue down that branch of the tree.

[anonymous_user_759e5c3a]

Here is a tutorial for randomly wandering: A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums
Decorators are usually used as conditional checks for gates (e.g. If enemy is nearby, then path is open, otherwise skip it). Services are something that constantly trigger as long as the path through it is active.

Here is the new Quickstart Guide:

https://docs.unrealengine.com/latest/INT/Gameplay/AI/BehaviorTreeQuickStart/index.html

[AmareshB (Amaresh Beuria)]

@;122103

Decorators are usually used as conditional checks for gates (e.g. If enemy is nearby, then path is open, otherwise skip it). Services are something that constantly trigger as long as the path through it is active.

Thanks for your answer, but I was asking specifically about those 3 decorators used in the image. Got the point about those in the unreal documentation though.
What does the Reached Goal Decorator indicates when inverted. From what I understood is that it is to check if it hasn’t moved to the target location. Am I right?

I’ve done the wandering part. Now the behavior tree looks somewhat like this:

[anonymous_user_759e5c3a]

@;122276

From what I understood is that it is to check if it hasn’t moved to the target location. Am I right?

That decorator should look to see if the AI has not gotten within a certain range of the goal.

The other two decorators in the original image are just “Checks” essentially, seeing if values have been set (or not set) in the Blackboard.

Let me know if anything is not behaving as expected or if you have any other questions.