There’s no weight painted under the neck. You don’t have to care about other vertex groups, I already checked many times, there’s no weight under the neck.
However when I rotate the neck bone, vertices at the end of the mesh still affecting on neck/head bones even it is 0 weighted:
Hum, maybe “use envelope” option is activated in the armature modifier ?
If that’s not the case , and there isn’t other deforming modifier on the mesh (meshdeform , lattice) …
Then I don’t see why it’s still deforming, try to erase vertex groups one by one to double check they haven’t any kind of influence…
Note also that if all the vertex group’s weight have a 0 value but only one as weights like 0.0001 (in the 0-1 range) it will still completely deform the mesh, because the higher value is then remapped to full deformation even if said value is quite low.
Hopes that helps , fortunately there are not that much possibilities for your issue to append, so I guess the solution is not that far !
@sozap, thank you so much! I found the bone that occurring problem. In weight painting mode, it doesn’t seems like it has weight(because it was just totally blue) but I just repaint all vertices under the neck with 0 weight and now it fixed! As you like said it must be very small amount of weight are assigned to the under the neck.
