P.S.: As an alternative, and perhaps similar in set up, but much faster to animate are these two examples (in one file).
I used a Fracture Object to introduce the Color for the Multi-Shader.
The color is then changed by “Radio Buttons” or “Quicktab Radio” options. They work pretty simple, you just name an Integer then a semicolon and the name of the button.
This Integer value needs then to be adjusted (divided) to have the values between 0.00 and 1.00 for the color (Yes we feed one value, which will be taken for R, G, and B at the same time, creating a gray value)
So, if you have 32 images and you have 32 buttons, divide the User Data value by 32 (or 31 to be precise, as the zero has to stay zero anyway…). I would set up many images as placeholders, so the system stays the same, even if you have more “expression-images” to add. Otherwise each new image (additional image) might screw up the set up or worse the animation so far)
The XPresso is set up for the Fracture as “Relative”, so you can save the XPresso (which contains the User Data) as Object Manager> File>“Save Tag Preset”, and call it up as often as you like.
If that set up works, and you need to replace/update a single expression: just got to the MoGraph Multi-shader, pick the texture and replace it. Done.
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The animation process is simple, just click on the button or check-box, and store the keyframe (perhaps select auto-keyframing).
If the animator is very familiar with the buttons, and the auto-keyframe is enabled, you could set the playback rate to 2 fps and click as you go. If a mistake has been made, overwritting is as simple as go back to the mistake, and click a different option.
I hope that is an option to consider.
My best wishes
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The numbers of the “sphere-faces” are just placeholders. The animation test was successful, and the third images shows the set up (the text can be copied even)