Layered blend per bone, not evaluating as expected

anonymous_user_1a56da39
Fri, 30 Oct 2015 16:52:01 +0000
Character & Animation

Hi, I’m trying to make the split body setup as seen in the fortnite demo video that was shown on twitch tv a while ago. [link][1]

Info on the anims:

Idle pose ref is and idle pose exported with bind pose cog and legs

walk_upper also has bind posed lower body and is additive, using idle pose ref as its base pose, very similar initial pose

walk lower has the full motion from the cog and legs, but the upper body is in the reference pose, ready to be replaced by the idle pose ref using the layered blend per bone node

I’m getting issues with the upper body additive rotating in the wrong direction. If I have the following chain of nodes it works fine :

This is the idle reference pose, with an upper body walk added to it, the result is the same as the upper body walk set to non additive. This is the desired result.

The point where I am getting stuck is when I introduce a layered blend per bone node to replace the lower body with a walk/ strafe animation.

Now I have the same idle ref pose, combined with the lower body replacement. When the blend value for the layered
blend per bone node is adjusted, there is no visual change in the spine posture. HOWEVER, when the additive is blended in, the spine will rotate differently depending on the blend weight on the layered blend per bone node. Changing the lower body animations at this point to a strafe blendspace will result in wildly tilting upper body animations.

This error does not occur or is negligible when the delta between the ref pose and the first frame of the additive is 0. Ie when testing the idle breathe animation in this setup (idle breathe uses it’s own first frame as it’s reference pose). When that is the case, the lower body animation can be absolutely anything and the spine stays rock solid as expected. It’s as if the layered blend per bone node is adusting the parent space of the top spine joint, so it rotates off axis as the animation changes beneath it. The layered blend node has the pelvis bone set to a blend depth of 0 and then a negative blend on the first spine joint. I’ve experimented with all the numbers but to no avail!

I’m wondering what I’m missing in my setup. I thought as the layered blend per bone node is locking the spine in the idle ref pose that the additives will play in local space on each bone?

I’ve tried changing rotation orders on me skeleton and also extracting the additive in maya and converting it into a reference pose relative animation and I get the same result. It definitely seems to be the layered blend per bone node confusing the axis.

Thanks for your time!

2 posts - 1 participant