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A Better Behaviour Tree - System

/ 2 min read

c++, ai, behaviour-trees, tools

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About

I recently found the opportunity to use and improve the behaviour tree system I made for the SFAS contest.

I identified some pain points when using it initially, but with the time restrictions of the competition, I didn’t really have the time to solve them.

Improvements

Here are some of the improvements I made:

  1. Decoupling
    • Behaviour trees previously made using my framework had nodes that were heavily coupled to the entity they were controlling.
    • I wanted to alleviate that using a better blackboarding system, and stripping out the node class from the behaviour tree class.
    • This would help me make more modular nodes, which could be re-used across different game entities.
  2. Smart Pointers
    • Nodes now use shared pointers so the tree will naturally de-allocate the nodes sequentially upon delete.
    • I re-use some nodes in my example behaviour tree, but as long as I don’t create cycles, it should de-allocate just fine.
  3. Vectors instead of lists
    • Initial implementation used lists instead of vectors. For composite nodes with only leaf nodes, there would be a performance benefit to traversing vectors instead. So I swapped out lists for vectors.

How To Use

This was used in a different project, so it has references to a GameEntity which is not in the folder. Please swap these references out with your own AI/actor base class if you intend to use it.

For examples on it is used, see:

  1. /ExampleBTs/ for example behaviour trees.
  2. /TaskNodes/ for example node services and actions.