Shape key driver posing affects the resting pose?

Question

So I'm working on a rig with eyelids that close via shape keys run by a driver. But when I go into pose mode to play with it and then switch back to rest mode or go into edit mode which would usually reset the pose, the eyelids don't go back to their own rest position.

Is this just a quirk of using shape key drivers? I'd assume there to be a setting somewhere to make it... not do that, and instead behave like all of the other bones in the armature. It's otherwise really inconvenient to always have to be resetting the eyelids to work on my model in its neutral state.

I'm using 2.82, I tried to google an answer but I don't really know how to word it simply I guess. Sorry if it's a dumb question, I'm still very new to blender and 3D in general, this is my first rig ever and I'm learning a lot :)

Answer 1

It all depends on how your driver is set up. There are multiple things your shapekey can be driven by. Some of those things are "at rest" in rest pose; some of those things aren't.

For example, if you drive from a "transform channel", that's the post-constraint, visual transform of a bone. Those all go to rest at rest.

But if you drive from a "single property" like pose.bones["Bone"].location[0] (which you get from copying the X position of the bone as a new driver), then what you get is the keyframed X translation channel of that bone, which is pre-constraint, and which doesn't go to "rest" in rest position. Rest position doesn't change your keyframes-- it just makes it so that they don't do anything. If that makes it any easier to think about.

So, if you want to change your drivers from single properties to transform channels, I think you'll find that rest pose sets your shapekeys back to their defaults (whatever those are.) Just be careful about it-- you'll need to specify the space of evaluation for the driver, and you'll be getting post-constraint values, and you'll no longer be getting rotation as your exact keyframed values (for example, you will never see a rotation of >180 degrees in your transform channel.)