Animation breaking


(Scoppens) #1

I'm currently working on a small level with some simple animations within it. There is a bird circling my level and its wings break apart as it flaps them.

I'm using Maya to build and animate this scene. It looks great in maya and I used an FBX review to check and see if it was the export, but it also looked good in the viewer. I have just been key framing translate and rotate to get my animations. I have tried animation through parenting the geometry and also by grouping the geometry. I have also baked out the key frames and still didn't have success.
Frame 1 is the only frame that looks how it should and the rest look like the pictures I posted.
If any one has ideas to help or some thoughts I would be very grateful to hear them.

Animation problem--meshes wander off their axis

Hi Spencer,

We're investigating.

(Systmh) #4

I think I'm having the same problem. Haven't found a workaround yet, but I'm considering rebuilding using skeletal animation. Does your scene have a long timeline, more than 3000 frames?

Here's my thread and examples of the issue I'm having. Does this look familiar? Do you have your scene uploaded?

(Scoppens) #5

Hey, it does look fairly similar to what I had happen with my scene. I found an older version of my scene if you want to see how it was breaking. . This version of was using 30 fps and had only 300 frames in the scene. I later changed it to 24 but still had the same issue. As you can see the animation falls apart right away but that might just be because the movement is a bit faster than in your scenes. I had tried a couple different things to see if it would work and none of them ended up solving my problem so I ended up scraping the bird from my scene. I had also adjusted the pivot for each of the pieces of the wing so perhaps that is where the problem lies?



So it looks like there are multiple nodes (2 birds) with the same name. If you remove this, it works:

PIAF by mrchlblng on Sketchfab

(Scoppens) #7

Thank you James for getting back to me, I really appreciate it!


No problem! Sorry for the long silence :sweat_smile:


@scoppens just a note that we're still digging into this, there could be other issues so we're looking for a fix :smile:

(Waleguene) #10

Hi @scoppens ,

We investigated your model and found that the way the animation was defined is not supported by Sketchfab.
In fact, the issued nodes are rotated around some far rotation pivots and then compensated by big translations.

When a keyframe is defined, this is ok since the values are the good ones and the compensation works, but between two keyframes, rotation and translations are interpolated and this is precisely at this moment that you get these huge offsets. The values got by interpolation doesn't compensate each other.
A way to get it work would be to play the animation frame by frame, with no interpolation.

Also note that there is also a small offset introduced by our animation compression that is logged on our side, for what we will provide a fix asap.

Now, we can explain the result obtained above (fixed) by the fact that we have reimported your model into 3dsMax to make the mentionned changed. An FBX import is sometimes followed by some internal processings that converts data to be correctly handled by the software. So, the import-reexport changed the internal data in a way that the animation can now be interpolated and played correctly on Sketchfab (by centering pivots/offsets for example).

For your case, a workaround could be to convert your keyframes to "Step/Constant" interpolation keyframes, to avoid to have buggy transition values.

I hope it helps :smile: