AnimationTree: transition with xfade from a state machine start with wrong animation.

[gui1117]

Godot version

Godot Engine v4.0.stable.official.92bee43ad

System information

Linux, Vulkan API 1.3.224 - Forward+ - Using Vulkan Device: NVIDIA - NVIDIA GeForce GTX 1650 Ti with Max-Q Desig

Issue description

In AnimationTree, a AnimationNodeStateMachineTransition with Xfade Time set to 0.5 between a StateMachine and something else is wrong at the beginning.

When starting to transition at first it shows the first animation of the animation player for one or few frames. Then it does the smooth transition as expected.

This issue arise when transitionning from a StateMachine to a StateMachine or from a StateMachine to just an Animation

Steps to reproduce

have a glb with 3 animation.

Make an AnimationTree with a StateMachine and animation 3, in StateMachine have animation 2, and do a transition with xfade time 0.5

Minimal reproduction project

At https://github.com/thiolliere/GodotBugStateMachine
run it and click StateMachineStateMachine or StateMachineAnim and then click Start and the issue may show.
click again on StateMachineStateMachine or StateMachineAnim and then click Start and the issue may show again.

[gui1117]

I made a screen capture: because of capture quality only first time the issue is visible.
Capture vidéo du 2023-03-11 11-33-18.webm

and I run the capture frame by frame in vlc, you can see that it does TPose for one frame which it shouldn't be
Capture vidéo du 2023-03-11 11-34-39.webm

[gui1117]

thank you