Negative animation speed ratio behaves differently between beginAnimation and beginDirectAnimation

Bugs
1

When have negative speed ratio, beginAnimation will jump to the last frame and stop, while beginDirectAnimation will just stop at the first frame.

I think the expected result for both functions is to reverse the animation, like animationGroup do.

The most weird thing is the two function behaves differently.

2

There is no shared playground in the link, would you be able to provide the snippet?

3

Sorry for the wrong link. I have updated it.

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4

So - I agree with everything you wrote TBH.

The reason for the different behavior are these lines:

Babylon.js/packages/dev/core/src/Animations/animatable.ts at master · BabylonJS/Babylon.js (github.com)

This flips the to and from (but not the speed ratio). I will need to dig in a bit and see why it is done this way. If we are already flipping to and from, we should also revert the speed ratio (which would reverse the animation).

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5

Just something quick - the to/from should have been adjusted. If adjusting to the actual frames you have provided, the direct animation works as expected: Negative Animation Speed | Babylon.js Playground (babylonjs.com). Still figuring out a few things.

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6

This solves the issue, but I would be happy to get the opinion of other members of the team :slight_smile:
treat negative speed ratio at the animate function by RaananW · Pull Request #15509 · BabylonJS/Babylon.js (github.com)

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