Initialization of MjScene in Unity

[Balint-H]

Sometimes scripts and behaviours need to initialize with information from the MjScene. Since MjScene itself initialises on Start this can be tricky, since the instance may not have already been created. I've been using workarounds as discussed in #360. Is there a better way than these available?

Why is MjScene is initialised on Start instead of Awake? That could make this simpler potentially. Alternatively, if initialising on Start is important, an event called when the scene is created, that behaviour's could subscribe to would be handy.

Lastly, on a couple occasions I ran into issues with scripts whose clean-up (OnDisable, OnDestroy) code depended on either the state or existence of the mujoco scene (i.e. if it was destroyed already or not). In these cases what is the right way to check if its still instantiated? Checking MjScene.Instance == null unfortunately creates a new scene if it was already destroyed due to the singleton pattern. public static bool InstanceExists { get => _instance != null; } or something similar would be helpful in those cases.