Can I merge multiple objects into one, while keeping the rig working? So I was following this guide of creating a low poly person and rigging it, and as you can see he created a person from multiple cubes and spheres and connected them to one rig manually, by selecting each object and connecting it to a proper bone. That works beautifully and it's simple, intuitive, and fast to me.
Now I wanted to import my model with working rig to Unity, and he also has this guide. The first problem is that he uses a model that is a single object, so I just use Ctrl + J to merge all cubes and spheres into one object, but it breaks the rig completely. Here he uses automatic weights and weight paint, and both of these work terribly in my case. I wouldn't have such a big issue with facts like the forearm actually moving some bits of my legs as well if the weight paint tool wasn't so painful to use for me. I struggle so much to remove every bit of paint anywhere besides where it should be and, even if I succeed, I can never get it to work as it used to while using the first method (like forearm scaling down and leaving the bone while rotating for whatever reason).
Is there any way to somehow merge these objects and keep the skeleton working? I do realize that the rig breaks because references break when I merge the objects, but there's a couple of reasons why I wanted it to be a single object, like changing the center of the whole object to the bottom and make it work so I can animate it with Unity.
For the rigging of machines / robots / non-organic objects, etc. you have 2 methods.
If you want to keep separate objects, use basic parenting: Select on piece, shift select the armature, switch to Pose mode, select the bone you want and CtrlP &gt; Bone
If you want to join all your objects into on (i.e. your case), parent with vertex groups:

Select all your objects, join them with CtrlJ
Select the object, shift select the armature, press CtrlP &gt; parent With Empty Groups (which is going to create vertex groups in your objects but no vertex is assigned for the moment)
Go in Edit mode, select one part of tour object (example: the head), go into the Properties panel &gt; Object Data &gt; Vertex Groups, select the head vertex group (i.e. the vertex group that has the name of the bone that is supposed to control the head), click the Assign button under the Vertex Groups list, and so on