Unity: Create AnimationClip With World Scale AnimationCurves

Question

I've been looking for a solution to this for quite a while now (meaning several days) and I haven't found anything yet. Maybe I'm thinking about it wrong and there isn't a way, but let's try!

I'm recording hand-data on a Hololens (the Unity Hololens Input Simulation for now). This essentially gives me one float AnimationCurve for each hand joint for each transform.position.x to z and rotation.x to w . Now my goal is to put these curves into an AnimationClip and add it to an AnimatorController (via an AnimatorOverrideController ) that animates a hand rig and replay the recordings. Everything so far works!

However, the recorded hand-data from the Hololens is in world scale, not in local scale. (which makes sense, since you usually want absolute coordinates when you want to know where the hand is.) But to animate the hand, it seems I'm only able to set local coordinates, which I don't have.

Example:

clip.SetCurve("", typeof(Transform), "localPosition.x", curve.PositionX);

Here, the clip takes the the x-coordinates from some hand joint and puts it to the localPosition.x of the corresponding hand rig joint. The problem: curve.PositionX is world-scale (absolute coordinates), but localPosition.x takes local-scale (coordinates relative to its parent).

I can't simply change "localPosition.x" to "position.x" , like so:

clip.SetCurve("", typeof(Transform), "position.x", curve.PositionX);

even though the Transform class has both properties and position is the object's world scale position. I'm not sure why this doesn't work, but it gives me the following error:

Cannot bind generic curve on Transform component, only position, rotation and scale curve are supported.

I'm aware that it doesn't make much sense to use absolute coordinates for an animation, but I simply don't have anything else.

Does anyone have an approach how I can deal with this in a sensible, not-too-cumbersome way? It seems I have all the important parts, I just can't figure out how to put them together. Thanks so much already! :)

Answer 1

From my basic understanding, it seems like you are using the Input animation recording service provided by MRTK. Unfortunately, MRTK does not provide the localPosition version of Curves data. However, you can modify the data from the recordingBuffer after the InputRecordingService stops recording.

So, this is a method worth trying for you: in the handJointCurves dictionary property of recordingBuffer field, a set of pose curves is stored for each joint. And then, base on this table: Joint pose curves , subtract the position value of the key None from the position value of each other joint in every key frame so that the localPosition based on the key None is obtained.