Rigging issue, disconnecting body parts

Question

not sure where to ask this to be honest, reddit pretty much takes down everything i type. But anyways, im trying to rig a model right. Humanoid. The model was a human i cut up to fit inside of a suit i made.

The suit isn't the issue, because the human by itself had the same issue, im going to be attempting to rig it agian in a few days and would love a head-start on how to fix this issue once and for all.

I try to look at videos online, but none cover this exact issue. In the past, I've tried weight painting, clear parents, assigning automatic weights, assigning troublesome parts to vertex groups and no matter what i do, the arms and head always disconnect from the rest of the rig after ARP creates it.

I don't have an image of the bones on hand, but i can easily replicate the problem and get them. I know for a fact the entire rig is connected, im using a blender Add-on called auto rig pro. Mixamo can rig the model with no issue but i need it from the add-on for my use case.

Any ideas would be appreciated.

Answer 1

Simply put, there is a hole in your mesh, and right now it is not rigged/weighted so as to not pull apart from the bone deformation.

You have two options:

1. Fill in the hole. How you should do this depends on what kind of hole it is. If, as I am guessing, the arm simply an open-ended tube intersecting the body, a Boolean operation with some smoothing afterward would probably work.
2. Make sure every vertice involved with the hole has the exact same weighting, so that if part of the hole moves, the rest moves with it, and it stays hidden. This approach is only recommended for situations where a hole really helps with modeling, and where the resulting block of deformation won’t look weird,