Documentation - update order

[huhund]

Describe the problem or limitation you are having in your project:

The update order of engine features such as input, animation, physics and collision response is unknown.

• It is important to know the order the engine executes to avoid hunting bugs that are expected behaviour depending on the update order
• Developers need to know the update order to minimise frame lags in the input->logic->render cycle
• The order of _integrate_forces() and _physics_process() works differently between 2D and 3D physics.

Describe the feature / enhancement and how it helps to overcome the problem or limitation:

Documenting the order of updates and callbacks, e.g. like this:
https://docs.unity3d.com/Manual/ExecutionOrder.html

[Calinou]

Related to godotengine/godot#37702.

[Calinou]

@madmiraal @aaronfranke Any pointers on this? (I don't expect anyone to know the execution order by heart, but help would be appreciated.)

[madmiraal]

The Main::iteration() loop function is here:
https://github.com/godotengine/godot/blob/db1eb909fe1e6067743892d7544160a1a40b9e43/main/main.cpp#L2116-L2270
Documenting what happens here will get you 80% of the way there.

[YellowOnion]

Is there any information on how say _process is run in a threaded system?

lets say I wanted to submit work to a thread, and then return that work from said thread in the same frame, how could I do that without blocking _process (which I assume would be bad as it would block all other _process's from submitting work) do I have to incur a single frame delay (read previous work, submit new work, exit function)?

it seems to be that using stuff like _input to submit work (asap) and then using (physics)process just to "read" from a thread?

it would be nice to know how to better manage expensive operations off the "scene graph".

[Calinou]

Closing in favor of #5492, which has more information about the issue at hand.