Thoughts on possible parallel-like state?

[andmish]

I've used State Charts and LimboAI for a while, making different character controllers, talking just about state management/transitions parts here. I think you can implement all of your intricate ideas and make complex state machines using any of two, but let's say, for some imaginary feature parity, LimboAI is missing "Parallel State" analog.

Personally, I really like LimboAI approach a lot more (initializing transitions using code, handy delegations, BTStates as states, etc.). It's just a pleasure to work with, basically covers everything state/ai related and I don't even want to use anything else now 😊

So, will it be difficult/feasible to add maybe a new node like LimboParallelHSM? Which will updates all its immediate children in "parallel" mode (obviously just from top to bottom and if the child is LimboHSM, that hsm updates its initial state too as usual?). In this case any transitions between children are not necessary and just ignored if you define them?
Maybe I'm missing something, what do you think?

For the example, I come up with this tree (but I bet if there is such functionality users can come up with much better use cases)

Character
┖╴States LimboHSM ✔_updates
  ┠╴Cutscenes LimboState
  ┖╴Gameplay LimboParallelHSM ✔_updates
    ┠╴Abilities LimboHSM ✔_updates
    ┃ ┠╴Off LimboState ✔_updates
    ┃ ┖╴On LimboHSM
    ┃   ┠╴SomeAbility1 LimboState
    ┃   ┖╴SomeAbility2 LimboState
    ┖╴Movement LimboHSM ✔_updates
      ┠╴Idle LimboState ✔_updates
      ┠╴Walk LimboState
      ┖╴InAir LimboState

In this tree character can be switched between Cutscenes (where its movement driven by animations from animation player maybe?) and Gameplay (where input is checked and you can control it).
Gameplay will be LimboParallelHSM. Abilities are off for now (and just waiting for input/enabling). Abilities are not tied to character movement (such as they are not affecting its animations/states directly, etc.), maybe one ability creates rotating rocks around character, updates the rotations and check collisions, and another could also overlay/blend different animations on top in animation tree, so it mixes with idle/walk animations nicely. So abilities are really parallel/overlayed things and character movement is fully separated and not depended on them.

I guess it can be achieved by making 2 separated LimboHSM (Abilities and Movement), but then it will need some other node to keep links and making checks? And what if I want 3 or 4 parallel states for some reason? In the example above everything sits nicely in one tree and can be controlled from the main States and its substates. I'd like such simplicity 🙂

[limbonaut]

I'd rather call it LimboParallelState - because it's not really an FSM, so this concept is more like a composition of states.
I generally like the idea, and thought about it in the past, but never came to need something like that in practice. Some API would need to change, though. For instance, LimboHSM.get_leaf_state() is not going to return a useful result with a parallel state.

[andmish]

@limbonaut yeah, LimboParallelState will be the best choice, it's already well-established term and matches State Charts naming too, so some users will already know how it works and what to expect from it