Bug: broken fbx animation

[tigert1998]

Describe the bug
The FBX animation support is broken in the latest master branch. However, animation still works in v5.3.1. So the latest several commits must have made animation broken.

To Reproduce
My model loader code is available at https://github.com/tigert1998/tiger-game-engine/blob/main/engine/src/model.cc.
You could build the instancing-demo CMake target to test.
The two models with broken animation (fbx version) are (these two both work in v5.3.1):

• https://sketchfab.com/3d-models/silver-dragonkin-mir4-89ead4e87cdc4b70840f748383f0998f
• https://sketchfab.com/3d-models/tarisland-dragon-high-poly-ecf63885166c40e2bbbcdf11cd14e65f

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Platform (please complete the following information):

• OS: Windows
• Version: latest master

Additional context
Add any other context about the problem here.

[tellypresence]

Confirm broken animation.

Model tarisland-dragon-high-poly
Animation	Screenshot
Qishilong_skill06

[JulianKnodt]

Can you double check if this is still broken? I broke the FBX animation with a change, and it was recently fixed.

[tellypresence]

Confirm that latest commit does not fix fbx animation; also confirm that animation was OK at release 5.3.1

Model tarisland-dragon-high-poly
Animation	Assimp
	feb861f (21 Mar 2024)	release 5.3.1
Qishilong_skill06

[tellypresence]

Updated Aug 2024: please refer to issue 5719 for detailed bisect reports which show that there was breakage at 27 Oct 2019 and 24 Mar 2020

Here are examples of fbx files where animation was working around release 5.0.1 but stopped working before release 5.3.1; models available using either

• direct link
• from renderpeople.com: under "3D Animated People" click "Free Download" button, then click the "FBX" button and download zip

Models of interest are

• 22-rp_manuel_animated_001_dancing_fbx
• 35-rp_sophia_animated_003_idling_fbx
• 55-rp_nathan_animated_003_walking_fbx

Model	Assimp version			Notes
	2d2889f (24 Sep 2019)	release 5.3.1 (25 Sep 2023)	feb861f (21 Mar 2024)
manuel dancing				Worked at commit 2d2889f and release 5.3.1, obviously wrong now
sophia idling				Worked at commit 2d2889f, didn't work in release 5.3.1, obviously worse now
nathan walking				Worked at commit 2d2889f, didn't work in release 5.3.1, no obvious difference now

Here's what they should look like...

[kimkulling]

Oh my gosh, that looks bad. I got it!

[shinyclaw]

Confirmed at version from today's master branch. Animation "Hip Hop Dancing" on model "CH42_NOPBR" from Mixamo.

Hip.Hop.Dancing.mp4

[mwestphal]

I've bisected the issue to #5349

[mwestphal]

Please note this is NOT the same issue as #3390

[kikonen]

Just tried to update from 5.3.1 to 5.4.0, and well, as a result got kind of abstract art, which looks similar to samples here.

[tellypresence]

@kikonen Are you able to share your test FBX model file(s) for troubleshooting purposes?

[tellypresence]

@shinyclaw Have you got a link to the Mixamo CH42_NOPBR model?

[kikonen]

@tellypresence I presume I can share files for testing, just can't share them publicly to everyone.

https://drive.google.com/drive/folders/1ZOLRK1X-lN3Jq6hxdJ6XPr-oFEk2xcng?usp=sharing

SK_Lion.FBX

• Got broken with 5.4.0 (worked with 5.3.1)

"Lion with 5.3.1"

Lion with 5.4.0

SK_SkeletonKnight.FBX

• Animation has not worked so far properly with assimp at all; aka. this may have separate issues, not related to 5.4.0, but just adding it here as secondary reference point

Skeleton animation, with assimp 5.3 - 5.4

[lxw404]

@kikonen Please try: #5643. I'm fairly sure I've fixed this regression, but it would be good to have more people verify it (and encourage that it gets merged).

[kikonen]

@lxw404 seems to improve animation result at least in my Lion.FBX case

without fix
Nice abstract art...

With fix
Expected result

Since goal in my project is not establishing abstract art exhibition, I prefer "boring expected result" :D

EDIT
Bonus points for the fact that "skeleton_knight.FBX" is not totally really weird mess any longer (w/ fix). Clearly having some problems, but at least can recognize more-or-less now what it is...

[lxw404]

@kikonen These abstract art ones are hilarious, but I agree the boring expected result is probably best long term.

I'm guessing the skeleton is a completely separate issue then if it has never worked with assimp in any version before. I could possibly take a look at that and see what's up at some point.

[kikonen]

Yes, that skeleton has some other issues. I don't know about earlier versions of assimp than 5.3.1, since that happened to be point of time when I introduced assimp into this project. But yes, that case had issues with 5.3.1 already, but as can be seen, with these latest fixes it has improved a lot (remaining issues, well, there is changes of bugs (gosh ,really) in my own code also, so to be investigated, I just gave up with that few months ago, but now changes to take another look).

[JulianKnodt]

I think there can be issues with multiple meshes in a single node (specifically I found some when exporting meshes with nodes with multiple meshes), but it would be useful to know the hierarchy of your scene

[tellypresence]

@kikonen
Thank you for the link. It looks like both the Lion and Skeleton Knight have 2 FBX files each, the main mesh plus a separate animation-only FBX file. Do you have any way to export a single FBX file containing both the mesh and animation data?

[kikonen]

If possible should separate that skeleton into another issue.

Regarding fbx files, not sure how easily I could get them into same file. I.e. original files were separate files (mesh + anim), so to merge them would propably have try importing them into Blender and merge them there (and Blender seems to have its own issues with fbx import).

[tellypresence]

@kikonen Please try: #5643. I'm fairly sure I've fixed this regression, but it would be good to have more people verify it (and encourage that it gets merged).

@kikonen Please sync your PR branch (it's out of date)

[kikonen]

@tellypresence Did some trial with #5643 fix with current assimp master, and it was working for me same way as nonrebased version in PR. Noticed additionally that base transforms for few static mesh fbx files I had exported from unreal seemed to work now better, i.e. previously I had to apply -90 degree rotation along X axis to them after importing (i.e. generic improvement from some fix along the way).

You probably meant that sync req to @lxw404 :)