Armature setup and animation with Vectors and Quaternions

[Penfold_Dangermouse]

Hi there,
I am doing some decompilation work for an old video game that has a proprietary file format.

the armature bones are described as such:

{
    name: bone_name,
    parent: parent_bone_name,
    to_parent: [
        rotation: Quaternion,
        translation: Vector3
    ],
    to_world_origin: [
        rotation: Quaternion,
        translation: Vector3
    ],
    to_local_armature: [
        rotation: Quaternion,
        translation: Vector3
    ],
}

animation file is described as follows:

{
    name: bone_name
    keyframe_timings: list[int]
    transformations: [
        [
            rotation: Quaternion,
            translation: Vector3
        ],
        ...
    ]

There are a variety of issues that I have, I want to mention them in-case it matters somewhere…

1. The original file format uses a Left Handed, Y-Up axis. For now, I don’t care that the skeleton and animation are incorrectly flipped / wrong axis.
2. I am unsure whether the Quaternions are using a (W,X,Y,Z) scheme or (X, Y, Z, W) scheme.
3. I am unsure whether the initial bone roll matters / taken into account.
4. I am not too familiar with Blender, and whilst I think I have the correct settings for the bones (such as the local location, inherit rotation, etc), I am not certain these are correct.

Skeleton
When constructing the skeleton:

• If the parent is blank, set the head to 0, 0, 0
• Set the tail using the translation to origin
• Set the bone roll by using: Quaternion().to_axis_angle()[1]
• use_connect = True, as I guess the Vector and Quaternion seem to be referencing the tail.

This seems to work fine. I end up with a “person-shaped” armature.
Note: At this point, most of the bone settings dont have much if any impact.
All of the issues I mentioned have no impact yet

_Note2: There is a bone that has 0 length, Blender doesn’t like this, so I have added a fractional amount in the Y axis)

Animation
When adding keyframes:

• I am creating a translation matrix with: Matrix.Translation(Vector())
• I am creating a rotation matrix with: Quaternion().to_matrix().to_4x4()
• full_matrix = translation @ matrix
• then applying full_matrix to the pose bone using PoseBone.matrix()
• Finally, I add the keyframe information with:
  • PoseBone.keyframe_insert(data_path="location", frame=keyframe_number)
  • PoseBone.keyframe_insert(data_path="rotation_quaternion", frame=keyframe_number)

and this is where my problems start to arise…

Does my methodology seem sound?
I can post the information that comes with the skeleton and animation if someone wants to take a deep dive into this.

Thanks!

[joseph]

@Penfold_Dangermouse

and this is where my problems start to arise…

What problems specifically? Show us the animation you want and the animation you’re getting

[Penfold_Dangermouse]

So I am trying to get this…

Here is the skeleton.
Note1: the above GIF was created on an earlier model, this newer model has “cloak bones”.
Note2: You can see the axis and rotation has not been adjusted. So the model appears to be face-down and horizontal.
Note3: You may notice some bones between the legs. I assume these were hidden when the above GIF was made.

here is an example of what I have…

I am trying to play with toggling on and off different features.
This was with

• use_local_location = True
• use_inherit_rotation = False
• Incorporating a “default” Bone roll
• “Fixing” the quaternion that was read in as XYZW to put the “W” at the front

I need to post the other two images separately

[Penfold_Dangermouse]

Here is the skeleton

[Penfold_Dangermouse]

Here is my animation…

[Sacha999]

Hi,

On the gif, the skeleton is standup, your is lay down.
Did you create the skeleton using skeleton vertices world position or playing with the skeleton quaternion hierarchy?