Is there a better way to rig this sphere? Automatic weights doesn't do what I want, and trying to fix it in weight painting doesn't fix it

Question

I'm trying to rig this sphere, and I used automatic weights. I want the bottom bone to act as a root bone that will move the whole mesh. But even with painting the entire sphere with strength 1, there is deformation. (I used automatic weights)

Sphere I want to rotate. I want the bottom bone to act as a root bone, which moves all vertices of the sphere in equal amounts.

In weight paint mode, I made sure the entire sphere is painted with a strength of 1

Results when the root bone is rotated on z-axis

Answer 1

You're doing 2 conceptual errors:

• 1 Setting a weight of 1.0 it's not enough to get a vertex stuck on its bone, because the vertex shift is always calculated in relation with all the assigned weights, and a "normalization" is applied, so that if a vertex has a weight of 1.0 relative to three different bones, every weight will be treated as if it was 0.3333....: if you move the bone 1 BU the vertex will move 0.3333 BU. In a similar way if a vertex has a weight of 0.01 related to a bone, and this is the only weight that this wertex has, it will be treated as a weight of 1.0: if you move the bone, the vertex will follow exactly.

• 2 Root bones are always set as "non deforming": the idea is not that a root bone moves all vertices of a mesh; instead, a root bone is parent of all the others bones of the armature, so that when you move the root bone all the armature moves and all the character follows.

To solve, select your root bone, uncheck its "Deform" option and set the bone parenting so that the root bone is parent to all the others bones. Then parent the character to the armature with automatic weights and use weight painting to adjust the deformations where needed.