@vx9, I spent a it of time debugging your scene. I can see that the code is working correctly. I validated that your additive animations are correctly changing weight as you change your slider, so the code seems to all be working. That lead me to looking at your rig. I am not a regular Blender user (I am guessing that you are using blender) but I found some things that I need clarification on. For example, you are driving the character’s head by a constraint to a bone named “lookAt” which is a child of the “spine” bone. The “spine.006” bone appears to be what the head mesh is skinned to, and is following the position of the “lookAt” bone. Since I only have the glTF to go from, I can’t see any constraints you put into the file, but is this assumption correct?
Driving pose:
Look pose:
Since I am seeing rotational data on the “spine.006” bone, I am assuming that the rotational data is getting baked out to the bone. However, I am also seeing some strange behavior when bringing your car gltf into the sandbox. When I change the animation clip currently playing to another clip, I often see the playhead at the bottom of the page stop, even though the animation is still playing.
I am wondering if you can use your workflow to create a simpler example with only three bones. Set it up like you originally did and save out a base animation and one to add on top. I am having a hard time deciphering what may be happening based on the complexity of this rig.
@sebavan, I don’t see a reason that the additive animation would not work, unless there is some data in the gltf that we don’t expect. The file validates when looking at it in the inspector and I can confirm the additive flag is set and weights are set correctly, but it appears that the add it not happening.