PredictiveSynchronizer

[elementbound]

:sparkles: Description

There are objects that need to participate in the rollback loop, but are not controlled by any input - e.g. moving platforms, interactive objects like doors, etc.

In addition to lacking input, these also depend fully on known state, so there's no point in synchronizing them.

Implementation

Introduce a PredictiveSynchronizer node. It would have a state configured the same way as in RollbackSynchronizer, but no input, nor synchronization-related properties.

It would gather all nodes implementing the _predict_tick() method and run them as part of the rollback loop.

Distribution

netfox core

Notes

• :question: Should there be optional state synchronization?
• Preferably implemented after HistoryBuffer in #358 so it can be reused

[krazyjakee]

Is the functionality that far from RollbackSynchronizer? I feel like we're missing an opportunity to simplify and avoid a whole new node.

For example, you could tweak a RollbackSynchronizer to handle an empty Input configuration. Or perhaps add a "Process Input" checkbox, which, if unchecked could hide the Input fields from the node.

StateSynchronizer could even have a "Predictive" checkbox to enable rollback for its synced properties but I think that would go against the "just like Godot" purpose of that node.

[elementbound]

That's a really important point @krazyjakee, I've been pondering that myself too.

On one hand, having a separate PredictiveSynchronizer would be a stronger distinction between "this is in rollback AND controlled by players" vs. "this just does its thing, but in rollback". It's another question whether this is such an important distinction :smile:

Having this as part of RollbackSynchronizer might be friendlier for users, as it's the same node, and can be re-configured easily.

Something I'm concerned about is that RollbackSynchronizer is slowly becoming a God class. Separating it into multiple components can help for a while, but still, much of the new features end up in that single node.

Either way, I think RollbackSynchronizer can already do this, it just needs better docs and support :smile: Before #321, it only simulated notes with known inputs. However, for fully predicted objects, there's no input. But now, with prediction enabled, it might just work. Will need to check and possibly document.