To help narrow this down a little, when you say that there are little jumps/peaks, is this on any particular curves (i.e. rotation curves in particular), or just any/all of them? Could you include a screenshot of these?

In T54459#490974, @Joshua Leung (aligorith) wrote:

To help narrow this down a little, when you say that there are little jumps/peaks, is this on any particular curves (i.e. rotation curves in particular), or just any/all of them? Could you include a screenshot of these?

Sure, great idea thanks!

Now that you mention it, most of the curves in the FBX file are rotation because I use IK for the feet and arms with non-deform bones that are not included in the export to have a less cluttered hierarchy. The IK goal bones had position animation data, and then the other bones end up with resulting rotation animation data. However, the hips, spine/chest, and neck bones were all fine! Those bones had no jitter in my animations.

The problems occurred mainly in the shoulder, upper/lower arm, and hand bones. The shoulders are not part of the IK chain, just the upper arm and the lower arm bones are. The latter two have Inverse Kinematic limits placed on them in the Bone tab in the Properties window in Blender.

Here's the smooth position animation data of the Hand L IK Goal bone as is in Blender before export. In Blender, the other bones don't have rotation animation data because they're being controlled by the IK bone constraint.

Then in Unity with the FBX file, here's a shot of the left shoulder and left upper arm bones with the jitter (rotation animation data)

Also I forgot to add a visual -- This shows the animation in both Unity and Blender, and the differences are most obvious in the arms. The feet and legs here look pretty fine - I can't tell that there's anything wrong with them.

Registered specifically to say that I found a solution for the same problem I was having with a different animation.

The problem for me was Unity's animation compression - on the Import window, Animation tab in Unity, you'll see the dropdown menu "Anim. Compression" towards the top. By default it will have Keyframe Reduction, which produced jitters, but if you turn it to "Off" the jitters ought to go away.

@Sybren A. Stüvel (sybren) Unfortunately no, I have tried that in Unity and it does not fix the issue.

@Carlos (ModLunar) Can you then make us a minimal example file that demonstrates the issue?

@Sybren A. Stüvel (sybren) Sure thing, I'll post that as a comment with file attachments & screenshots/gifs when ready? (I'll try to get it done ASAP, in the next week or so)

I am having a similar issue, the bones behave properly and as expected in the blender file but after exporting the FBX legs start to slide and jitter, it's more noticeable when the character is large, I tried almost every setting possible, How did you resolve this issue???

I'm having similar issue. I exported a character walking animation using blender 2.8.3 in fbx format. The animation works ok in Unity on my desktop PC. But when I run the game on android devices, the arms keep shaking when the machine is under load (when there are lots of objects on the screen). I think it has something to do with low frame rate.

@Roger (ragerma) This is likely not the same issue. If you can provide a *minimal* example that demonstrates this issue and that shows that it's a problem with Blender, please write a new bug report for it.

Hi, just found the post, I've been dealing with this issue for years (since 2016).
I believe it's not related to unity since the jitter appears if you reimport the fbx into blender too. It also seems to be tied to IK.

Here's an example file:

It actually seems pretty random and I usually can't replicate it, the attached file is the isolated leg of a character suffering from the issue.
To reproduce simply export the animation from the .blend to fbx and reimport into blender.

I'd provide more examples but I haven't managed to replicate it on simple rigs, help would be immensely appreciated.

@Michael (Nib) this is not a "post", this is a task in our bug tracker. As I also said to @Roger (ragerma), please write a new bug report, that follows the guidelines at https://wiki.blender.org/wiki/Process/Bug_Reports.

To help resolve a bug I would like to add another exaple. BlendFile contains both IK animation (source) and reimported FBX animation (result). Export settings are also provided.