Pelvis bones doesn’t make any sense to me as deformation bones. I know, I can just un-check deform box and they wouldn’t matter much after that point but i want to understand why they are there?
They are seems like they are parented to first spine bone and no matter which control/tweak bone I move they are just stuck to spine. Documentation writes they don’t have any control bones but they are useful, because of this i expected them to move according to other control/tweak bones.
Anybody notice any usefulness to pelvis bones as deformation bones?
You’re right, they don’t make any sense as literal pelvic deformation bones. Your real pelvis doesn’t deform.
There are two reasons to use them:
As helper bones, so that you get better autoweights. If you run autoweights without pelvis bones on a humanoid, your leg weights are probably going to extend too far up your torso. When used like this, it would be safe to just drop the weights onto the lowest spine bone, but that’s not necessary in Blender-- you can just hide the bones instead. (Not disable deform-- their weights matter.) A lot of Rigify facial bones serve the same purpose: not really intended to deform the mesh, just intended to hold the borders of other bones for autoweights.
Less often, but occasionally, you can use pelvic bones as fan-style bones with the leg. The pelvis doesn’t deform, but when we look at people, we’re not looking at their bones. We’re looking at their flesh, which doesn’t follow the bones exactly. If you make a model do the splits, a spine and two legs aren’t going to be enough to get great deformation at the hips-- the fold will be too strong.
For using auto-weight, it does makes a lot of sense now.
I guess doing things like splits make sense too, though it would require a little change in the rigify rig because those bones doesn’t move at all as it is.
Thanks for the info about face bones too, for me as few bone as possible is best. So i think removing deformation from those bones and adding those weights to head makes a lot of sense in my case.
