Texture keyframe ignored in continous update mode

[timothyqiu]

Godot version

4.2.dev6, master[6916349]

System information

Arch Linux

Issue description

Texture keyframe seems ignored when the track's update mode is set to Continous.

• This happens regardless how many keyframes are on that track.
• This does not happen in 4.2.dev5.

CC @TokageItLab

Steps to reproduce

Use the MRP, or create two animations by

1. Create a keyframe for Texture of Sprite2D node.
2. Change the update mode of the newly created track to Continous.

Switching between different animations in the Animation editor:

• Expected: Sprite2D shows the corresponding texture. In the MRP, it should show a red square for red animation, and a green square for green animation.
• Actual: Texture not updated after switching animation. The keyframe is ignored.

Minimal reproduction project

test-4.zip

[kyle-wannacott]

I was going to open an issue, but pretty sure my issue is the same as this; as animation doesn't show when set to continuous.

minimal project
invisible_character_animation.zip

What should look like when the project is ran:
https://github.com/godotengine/godot/assets/49783296/c076b89b-9fd0-4ffa-9459-de98deee966c

The animation doesn't show on 4.2.dev6

[TokageItLab]

Previously blending between different update modes was not allowed in AnimationTree, so the AnimationMixer implementation internally enforces Continuous when different update modes are blended. I will look into what the problem is.

[TokageItLab]

After some investigation, I found a slightly larger cause. It is possible to say that this is a regression for AnimationPlayer, but it is a latent bug that has existed for a long time that has come to the surface.

To begin with, the old AnimationTree did not allow continuous blending in cases such as Resource replacement.

Prior to the implementation of AnimationMixer, this worked for AnimationPlayer because AnimationPlayer and AnimationTree had separate processes for applying blends. The recent implementation of AnimationMixer is based on the old AnimationTree blend application process, which was affected.

So, perhaps we need to add a fundamental blending (transition) method for the resource assignning, which would require a slightly larger fix.

[TokageItLab]

In the meantime, I sent #83030 as a band-aid for 4.2.stable. I will send a proposal later for a proper implementation in the future.