Get so-called "root bone" using Unityscript/c#

I've posted it already on your other question as comment, but once more ;)

A SkinnedMeshRenderer doesn't have somet$$anonymous$$ng like a root bone. It doesn't even care about the bone-$$anonymous$$erarchy. The SkinnedMeshRenderer just needs an array with all bones in the order they are bound in the mesh. T$$anonymous$$s reference is setup by the Mesh importer. It creates the bone $$anonymous$$erarchy and assigns all bones to the bones array. In the Mesh a vertex can be bound to 4 different bones. The bones are specified by a bone-index. T$$anonymous$$s index is related to the bones array of the SkinnedMeshRenderer.

Again, the bone-$$anonymous$$erarchy is irrelevant for the SkinnedMeshRenderer. The $$anonymous$$erarchy is just an automatic way for affecting subbones, but on the skinning level there are just bones.

Another important array is the Mesh.bindposes - array. It specifies the "resting position" of each bone. The example shows how to create a very very simple model with two bones.

It's almost impossible to "simply" assign a bone structure to a certain skinned mesh because you have no idea of the bones order. You can of course try to determine w$$anonymous$$ch bone belongs to w$$anonymous$$ch index by calculating the mean of all vertices that are affected by a bone. That usually gives you the approximate position of the bone, but it's not really reliable.

For imported models, the connection - information is imported by the MeshImporter and is stored in the bones array.

edit

Here's an example print of our player characters bone array:

 Bone index:0  Name: Bip001 R T$$anonymous$$gh
 Bone index:1  Name: Bip001
 Bone index:2  Name: Bip001 R Calf
 Bone index:3  Name: Bip001 R Foot
 Bone index:4  Name: Bip001 L Foot
 Bone index:5  Name: Bip001 R Toe0
 Bone index:6  Name: Bip001 Pelvis
 Bone index:7  Name: Bip001 Spine
 Bone index:8  Name: Bip001 Spine1
 Bone index:9  Name: Bip001 L T$$anonymous$$gh
 Bone index:10  Name: Bip001 R UpperArm
 Bone index:11  Name: Bip001 R Forearm
 Bone index:12  Name: Bip001 R ForeTwist
 Bone index:13  Name: Bip001 RUpArmTwist
 Bone index:14  Name: Bip001 R Hand
 Bone index:15  Name: Bip001 R Finger0
 Bone index:16  Name: Bip001 R Finger2
 Bone index:17  Name: Bip001 R Finger1
 Bone index:18  Name: Bip001 R Finger01
 Bone index:19  Name: Bip001 R Finger21
 Bone index:20  Name: Bip001 R Finger11
 Bone index:21  Name: Bip001 R Clavicle
 Bone index:22  Name: Bip001 Neck
 Bone index:23  Name: Bip001 Head
 Bone index:24  Name: Bip001 L Clavicle
 Bone index:25  Name: Bip001 Jaw
 Bone index:26  Name: Bip001 L Calf
 Bone index:27  Name: Bip001 L Toe0
 Bone index:28  Name: Bip001 L UpperArm
 Bone index:29  Name: Bip001 L Forearm
 Bone index:30  Name: Bip001 L ForeTwist
 Bone index:31  Name: Bip001 LUpArmTwist
 Bone index:32  Name: Bip001 L Hand
 Bone index:33  Name: Bip001 L Finger0
 Bone index:34  Name: Bip001 L Finger2
 Bone index:35  Name: Bip001 L Finger1
 Bone index:36  Name: Bip001 L Finger01
 Bone index:37  Name: Bip001 L Finger21
 Bone index:38  Name: Bip001 L Finger11

As you can see the first bone isn't the root bone (Bip001). It conpletely depends on how the model has been created and how the modelling software has exported the bones.

There is no general rul how you "usually" add bones to the array. It doesn't matter, it's just important that they are in the same order you used in your Mesh.

edit: (Let's make t$$anonymous$$s answer a bit longer x) )

Here's the $$anonymous$$erarchy of the bones, just as reference:

 Bone Hierarchy:
 Bip001
 |--Bip001 Footsteps
 |--Bip001 L Weapon
 |--Bip001 Pelvis
 |--|--Bip001 Spine
 |--|--|--Bip001 L T$$anonymous$$gh
 |--|--|--|--Bip001 L Calf
 |--|--|--|--|--Bip001 L Foot
 |--|--|--|--|--|--Bip001 L Toe0
 |--|--|--|--|--|--|--Bip001 L Toe0Nub
 |--|--|--Bip001 R T$$anonymous$$gh
 |--|--|--|--Bip001 R Calf
 |--|--|--|--|--Bip001 R Foot
 |--|--|--|--|--|--Bip001 R Toe0
 |--|--|--|--|--|--|--Bip001 R Toe0Nub
 |--|--|--Bip001 Spine1
 |--|--|--|--Bip001 Neck
 |--|--|--|--|--Bip001 Head
 |--|--|--|--|--|--Bip001 HeadNub
 |--|--|--|--|--|--Bip001 Jaw
 |--|--|--|--|--|--|--Bip001 Xtra01Nub
 |--|--|--|--|--Bip001 L Clavicle
 |--|--|--|--|--|--Bip001 L UpperArm
 |--|--|--|--|--|--|--Bip001 L Forearm
 |--|--|--|--|--|--|--|--Bip001 L Hand
 |--|--|--|--|--|--|--|--|--Bip001 L Finger0
 |--|--|--|--|--|--|--|--|--|--Bip001 L Finger01
 |--|--|--|--|--|--|--|--|--|--|--Bip001 L Finger0Nub
 |--|--|--|--|--|--|--|--|--Bip001 L Finger1
 |--|--|--|--|--|--|--|--|--|--Bip001 L Finger11
 |--|--|--|--|--|--|--|--|--|--|--Bip001 L Finger1Nub
 |--|--|--|--|--|--|--|--|--Bip001 L Finger2
 |--|--|--|--|--|--|--|--|--|--Bip001 L Finger21
 |--|--|--|--|--|--|--|--|--|--|--Bip001 L Finger2Nub
 |--|--|--|--|--|--|--Bip001 L ForeTwist
 |--|--|--|--|--|--Bip001 LUpArmTwist
 |--|--|--|--|--|--|--Bip001 L Shoulder
 |--|--|--|--|--Bip001 R Clavicle
 |--|--|--|--|--|--Bip001 R UpperArm
 |--|--|--|--|--|--|--Bip001 R Forearm
 |--|--|--|--|--|--|--|--Bip001 R Hand
 |--|--|--|--|--|--|--|--|--Bip001 R Finger0
 |--|--|--|--|--|--|--|--|--|--Bip001 R Finger01
 |--|--|--|--|--|--|--|--|--|--|--Bip001 R Finger0Nub
 |--|--|--|--|--|--|--|--|--Bip001 R Finger1
 |--|--|--|--|--|--|--|--|--|--Bip001 R Finger11
 |--|--|--|--|--|--|--|--|--|--|--Bip001 R Finger1Nub
 |--|--|--|--|--|--|--|--|--Bip001 R Finger2
 |--|--|--|--|--|--|--|--|--|--Bip001 R Finger21
 |--|--|--|--|--|--|--|--|--|--|--Bip001 R Finger2Nub
 |--|--|--|--|--|--|--Bip001 R ForeTwist
 |--|--|--|--|--|--Bip001 RUpArmTwist
 |--|--|--|--|--|--|--Bip001 R Shoulder
 |--Bip001 R Weapon

I've used t$$anonymous$$s little script:

 public SkinnedMeshRenderer R; // assign in the inspector
 public Transform RootBone;    // assign in the inspector
 
 string ProcessBone(Transform aBone, string indent)
 {
     string result = indent + aBone.name + "\n";
     foreach (Transform T in aBone)
     {
         // Had to exclude other gameobjects since we have attached armor parts
         //Now only gameobjects are included that contains "Bip" ;)
         if (T.name.Contains("Bip")) 
             result += ProcessBone(T,indent+"|--");
     }
     return result;
 }
 
 void Start ()
 {
     Transform[] bones = R.bones;
     string text = "Bone array:";
     for(int i = 0; i < bones.Length; i++)
     {
         text += "Bone index:"+i+"  Name: "+bones[i].name + "\n";
     }
     text += "\nBone Hierarchy:\n";
     text += ProcessBone(RootBone,"");
     Debug.Log(text);    
 }