Animation cubic easing direction reversed

Cubic easing’s direction appears to be reversed when playing an animation on a Humanoid. For instance, according to this, with the “In” direction the motion should start slower at the beginning and become faster toward the end, however it actually behaves like “Out”.
This bug affects In/Out easing directions but not “InOut”, nor does it affect Elastic and Bounce easing styles. TweenService’s Cubic easing is not affected either.
This happens 100% of the time, both in Studio and in a live game, and both when playing it on a client or server; the old animation editor was also affected. The new animation editor behaves as expected, which results in the preview not looking like the final result.

CubicTest.rbxl (27.9 KB)

To reproduce the bug, just create an animation that uses Cubic easing in any keyframe, load it into any rig with a Humanoid and play it. Here’s an example:

Keyframe properties:
Playing the animation in-game:
Playing the animation in the editor:

As you can see, the animation editor works as expected, while the in-game animation doesn’t.


does this have any possible interaction with physics ?


You mean as in physics interfering with the animations?


yeah, is there ANY force at all, that could have an affect ?


I doubt it… I even tried on a custom rig with only two parts (one of them anchored, the other welded with Motor6D), and with Gravity set to 0 in Workspace. Uploaded the place in case you want to check it out:
CubicTest3.rbxl (23.9 KB)

Is there any way I could be absolutely sure?


My friend @Fierzaa ran into this problem today.
Will this receive an official response soon?


Encountered this a month or two ago, I had to reverse In and Out manually through the editor in order to bypass this. Not fun.


Just encountered this today. A front flip animation I was working on which previously played correctly in the editor now plays with reversed easing, the exported animation still looks correct when played


I’ve been suffering this problem as well. Real pain when I have to reverse everything. Roblox could we please get a potential fix for this?


I’ve just recently encountered this issue, it gives an effect of “stuttering” and reversing In-Out easing directions seems to fix the problem, and it’s only on recently uploaded animations


Had this exact issue last night and I was so confused! Just made a little short video, lol


Can confirm that this glitch still affects the latest version of Studio. It really sucks, since it means that the animation I see when editing is not the animation that is seen in game, and it makes my workflow super awkward since I have to manually reset every keyframe in order for it to look okay in game. It’s odd that nobody at Roblox has noticed yet considering the animation contest going on right now.


This is still a big issue slowing down development on a lot of my projects with a lot of animations. I do think at this point it’s worth not using the base animation editor instead opting for something like moon editor.

This wouldn’t be such a big issue if it weren’t for how badly getting the wrong easing direction can mess up an animation. It can turn the most natural and organic animations into something very choppy. I would very much like to see this problem fixed.

As for a fix for whoever stumbles across this? I would suggest going through and just set all your outs to ins and vice versa. Then switch to another editor for other animations until it is fixed.


Sadly it seems like Moon Animation Suite is for videos and not rig animations, unless I’m missing something. There’s the old animation editor, which has a slightly cumbersome interface and doesn’t support newer stuff like keyframe markers (in fact, it seems to erase them when you use it) or inverse kinematics, and besides that I haven’t found anything else.

Another thing that bothers me a lot with the default editor is having to align animations to frames. The worst part is that new animations often misalign when you load them because the editor chooses a different framerate, which makes it a pain to edit them. But I guess this fits better in a new thread…


You can use moon animator for animations. I do so for my own game. However I opted for the animation editor in this side project I’m currently working with some people on because I wanted something that took less setup to use.

Ultimately it seems even that little bit of setup with moon is not so bad. Furthermore there’s an entire discord community if you ever need help with it. I think I’ll just use moon from now on.


We’ll just have to live without IK until this is fixed unfortunately


I know we’re not supposed to bump topics, but this is ridiculous. You literally cannot use the default animation editor to make animations. (Still not fixed)


Thanks for the report! We’ve filed a ticket to our internal database and we’ll follow up when we have an update for you.

Please note that filling a bug report does not guarantee that it will be fixed once triaged.


affects InOut for me also, animations that should be super smooth seem to be snapping as if I am using a steeper easing function. might even be using Quad/Quint. Very bizarre behavior

the keyframes for the arms and legs use InOut, with the head/body using Out -> In -> Out -> In pattern


have you found a fix? like using another easing style to get the same effect or no