Root Bone Issue: 3Ds Max bug or am I ignorant?

junfanbl

Hello,

So, I've been trying to setup the root bone for my rig in 3Ds Max 2022. With the intention of importing it into UE4.

The steps I have taken to do this are:

1) Create a Root Bone and zero it out so it is center in both direction and rotation.
2) Freeze all Bones (in this case I also froze the spline controls)
3) Group the bones underneath the Root bone (parent) in the Hierarchy

As a quick test, I selected all the bones and geometry and exported them as an FBX. It to imported into UE4 without any issues. Now, I haven't applied any animations to it yet, but I haven't gotten that far.

The issue is when you save the scene in 3DS Max. After saving and reloading the scene the below issue occurs with some geometry out of place.  

Is this a bug in 3DS Max, or am I not adding the root bone properly?

Before The above steps:


After reloading the scene:

Ghogiel

It's kinda a bug in that it only fucks up when you reload, it should fuck up before that. Anyway I would  expect something weird would happen since the eagle is probably skinned and you have modified transforms in the bone hierarchy. Skin seems to hold onto the transforms of bones from when it is first added, and changing them after you have skinned will probably come back to bite.

probably you will have to use skin utilities to copy the skin weights (copy from before the tranforms went wonky), kill the skin modifier on the object, reset it's transforms to be sure, add a new skin and then the bones into there. Then use skin utilities to reimport the skin weights from the mesh copy you made earlier.

spacefrog

Are you exporting and REIMPORTING the scene in 3ds Max via FBX ? ( the white control object colors suggest something like that )
Is this a CAT rig or a standard 3d Max bones rig ?

junfanbl

I've only been using a .max file to save my work. No FBX. The controls in the image are frozen, that is why they're white. I guess I can try Ghogiel approach for the long term solution. In the mean time I've been able to get the skeletal mesh into Unreal Engine with no problems. Not sure how things are going to work when I get to animation though. We shall see. 

As far as the rig is concerned, it's a standard 3Ds Max rig. Thanks again!     

spacefrog

hmmm - my only guess ( without the scene ) is that during the skinning process of the wing parts ( those which  get offset at reload ) you have introduced some unintentional translation to the mesh, or similar
does the geometry jump when you toggle (enable/disable) the skin modifier on that part ?