I'm trying to rig specifically just a character face (Floating head situation, no need for body rig.) I tried the newer rigify that generates a face bone structure, but when I generate the rig, the bones don't deform and if I try to pair with automatic weight, the mesh doesn't move at all. What are some of the reasons rigify won't work?
Rigify doesn't work that way. In order to use it correctly, here are the steps :
Add Rigify rig from the add menu, which creates a "metarig". The "metarig" is a simplified rig without any interesting feature, his goal is only to be a temporary rig used for placing correctly the full-featured rig. He should not be used as a deforming rig.
In edit mode, place the metarig's bones correctly on your model. (You can find a bone positioning guide here) Do not delete nor add bones in the metarig.
When it's done, go in the Metarig's Armature Tab and click the "Generate Rig" button under the "Rigify buttons" Pannel.
This will generate a full featured rig according to how you placed the metarig's bones.
Now if you want, you can delete all the unwanted parts (and the "metarig").
It's time to bind your rig to your object. First, in the Armature Tab, you need to switch to the layer containing the deform bones, which should be that one :
All the bones in that layer should have a "DEF" prefix, meaning they are "DEForming" bones. If not, try the other two next layers. Then you select your objects to bind, then your armature, and you hit Ctrl P → Set Parent to Armature With Automatic Weights.
This should be enough to get your face rigged and skinned. It may not be perfect tho, so I encourage you to do some deforming tests, as well as some facial expressions in order to quickly identify deforming issues and being able to fix them via weight paint mode.
I hope I helped.
You are telling that, if you try to pair with automatic weight, the mesh doesn't move at all. It means it has a problem with weight painting.
To paint Your mesh first select your armature and then shift + select your mesh and then go to weight paint mode. Now you can paint your mesh as you want by selecting different bones. like upper eye bone for upper eyelid and lower eye bone for lower eyelid etc. also check this link