Splitng animations in Unity modifies tangent on last key frame

Have you ever imported an animation clip and attempt to split it in unity? Did you notice that all the animations that looped often looked wonky?
The problem unfortunately is with unity and not you. Unity is modifying your tangents once you split the animation. I noticed it change the tangent on the z rotation of the last frame of every clip.

Repro Steps
Duplicate your animation, add it to your model.
Select your model
Open the animation editor window
Check the transform of each joint especially the tangent of the last key using Unity's animation editor.

Did you spot it? Yes thats right unity is modifying your tangents


Mild case

Worst case


BTW the animations I imported had keys on every frame hence it was very easily spotted.

You might want to check other keys in case the problem is much bigger

 

Anyone know a solution to this? I have this problem as well with my animation clips. To solve the issue I subtracted the last frame from each clip and checked the box to tell unity to create a looping frame. This works but it would be nice to know why unity is messing with the tangents

 

Well i clicked on the second to the last frame and set both tangent to linear. This might be a problem if you don't have every frame keyed or if the curve is not meant to be linear. I have over 1000 animations and i do not see myself deleting the last frame of each one or even fixing the tangents so I plan on writing an importer.
You may have to do the same.

 

This is turning out to be a nightmare. I hate the fact Unity often choose not to explain some of there more technical functions.

 

What is the case number of the bug report with attached repro case?

 

Case 412828

 

Has anyone figured a way around this aside from deleting the last frame? It doesn't work for me at all. I'd like to know why Unity is doing this and has caused numerous issues with multiple projects I'm working on. What boggles my mind is is the first time I imported one particular file it worked perfectly as expected, but after importing the file into a new scene I am getting these tangent glitches no matter what I do. I've tried baking the keys in maya, I've tried turning off the animation compression, I've even reverted to an older fbx exporter for maya which worked temporarily. I'd just like to avoid having to go back and modify lots of animations which are not broken.

 

In the reported case 412828 the problem is caused by precision errors because the source animation has keys at very high numbers in the 30000-40000 range. Splitting up the source animation into several smaller files (using the @ notation - see the docs) with fewer animations in each, and moving the keyframes so they're closer to 0 should be a workaround for the problem.

If you have experienced the problem for a source animation that doesn't have very high frame numbers, please report a bug with a repro case that includes that source animation, because we have not seen that ourselves.

 

sorry to necro but, I'm having this since forever, now I'm using 5.4b10 and this bug is still there, I'm cutting off the first and last frame of the animation clip on the unity animation editor (model import settings) as a workaround but then my animation gets shorter, in a walk animation the leg doesn't stretch all the way forward like it should.

All my animations are made by hand, I keep all of them in a single .ma file, I think all my animations together are 144 frames long, even if I only had idle, walk and run (72 frames), the walk animation wont loop correct.

 

Okay. In that case, like I wrote, please submit a bug with repro case. We cannot fix the bug if we cannot reproduce it, and as far as I'm aware, we haven't seen this ourselves so far.

 

Hey @runevision , I just submitted, the case number is 784923.
I included a reproducible example.

 

Thanks! It should hit Animation Team when the bug report has been processed by QA.

 

You guys were able to reproduce this? This bug came back in beta 5.5, in 5.4 in the animation's tab of the import settings's preview pane it was still playing wrongly but in play mode everything seems okay, and now in 5.5 everything is wrong, setting Anim. Compression to off seems to fix a bit but there is still an issue in the very first frame of the animations which makes the animation to not loop correctly.
I started a thread in 5.5 beta forum, I was wondering if I could reuse the case:
https://forum.unity3d.com/threads/weird-shaky-animations.439442/

 

Hmm, this is bad news, now that I'm making animation clips duration multiple of 10. It will be hard to keep track of the anims even with a sheet. :/

But I still can't understand why this is happening, I tried baking the animations in maya and I don't see this interpolation issue, also, what this toggle here does?

It looks like it doesn't change anything! Isn't it supposed to not resample the curves left by maya if set to false?

But I still find this too weird, for example I have this creature model, the first animation clips were made with a duration of 24 frames, ok, the first clip goes from 1 to 24 (It's the first animation, a TPose and there is no animation at all in it) and the next clip starts at 25, In this clip, the frame 1 looks ok, the frame 23 and 24 also looks ok, but there is a "bump" in it at around 23.5! Why does that happen, if the frame that is totally different starts at 25 why do I get this interpolation in the middle of the frame 23 instead of in the frame 24 onwards? Of course I understand that having one extra frame between clips fix this but having a frame "space" (in this case, the space between 24-25) shouldn't also fix it? If I set the frame to be from 1 to 24 it should end in the frame 24 (beginning of it) and not get any curve after it, and this is is working in Unity, but the problem is that the interpolation error happens before 24, like there was a key frame at around 23.5, and the values there has nothing to do with the frame 25. Just for testing a setup a clip going from 23-24 and in the middle of it you have the exact pose you have at the frame 25, again 23 ok, 24 ok, but 23.5 it's wrong!

I don't know exactly how to explain exactly so I uploaded a video:

Here is a summary:

 

Ah, another thing I discovered, unity allows you to see the baked animation in the animation window as curves inside Unity (if you don't optimize the gameobject rig):

I created an animation clip going from the infamous frame 23 to 25. As I can see, even though frame 23 and 24 (0 and 1 in the animation window) has the same values, Unity insists in modifying the tangents between them, I don't think this is an issue with maya baking the frames.

edit: btw, thank you for taking your time for checking this issue.

 

That was an amazing explanation! Thanks a lot for taking your time for setting this up!
I will use this workaround for my animation clips for sure.

And that's all, case 784923 can be closed!!