Question Blend Face Capture animations with other animations?

I've been recording some Face Capture animations. While some of the expressions looks pretty good, there are times I'd like to rely on some specific "emotion" animations (Angry, Happy, Sad, etc) defined by adjusting blend shapes.

Since the Face Capture clips record values from the Face Actor component, rather than recording the resulting blend shape modifications, it seems I can't easily combine Face Capture with standard blend shape animations. I'm just wondering if there's something I'm missing.

For example, here's an Angry animation:



I'd like to be able to enable this, then have the Face Capture animation layer on top of this:



Currently, it's either-or.

Is there possibly some approach to having Face Capture record animation clips that output the blend shape changes to the various SMRs, rather than to the Face Actor component?

 

I played around with this a bit, creating an editor tool that mostly converted a Face Capture animation clip into a standard animation clip that only affects blend shapes. (I say "mostly" because I didn't figure out how to map the Head Rotation to the various Humanoid rig values needed to do humanoid head rotation.)

In any case, the results weren't really usable, as I couldn't figure out a good way to blend two animation clips together. My goal had been to play a "speaking" clip tat I recorded from Face Capture, and layer in various emotions from other clips that also affect blend shapes. But I didn't see a way to achieve this blending. Animator layers didn't seem to work.

In any case, a potential nice-to-have for Face Capture would be some way to inject some additional emotion into the capture. I'm imagining being able to hold down some keys on the keyboard to increase/decrease "sadness", or "happiness", or "anger". These are all fairly easily mapped from blend shapes, and I imagine them being blended with the actual Face Capture values. The final result can still be Face Capture's animation clips, but with the emotions layered on top.

I only say this because no matter what I do with my face, it's difficult to get as much emotion out of the character as I can get using something like CC4's Unity plugin. (https://soupday.github.io/cc_unity_tools/usage.html#facial-expression)