gltf how do you deal with latice references? - json

Question

I am working with the rigged figure gltf:
Not to post the entire gltf, i will post the relevant nodes:
{
"children": [
21,
1
],
"matrix": [
1.0,
0.0,
0.0,
0.0,
0.0,
0.0,
-1.0,
0.0,
0.0,
1.0,
0.0,
0.0,
0.0,
0.0,
0.0,
1.0
],
"name": "Z_UP"
},
{
"mesh": 0,
"skin": 0,
"name": "Proxy"
},
...
{
"translation": [
0.0,
0.06650590896606446,
0.0
],
"rotation": [
4.2157907720330458e-10,
0.9999844431877136,
-0.005583992227911949,
-7.549667913053783e-8
],
"scale": [
1.0,
1.0000001192092896,
1.0
],
"name": "neck_joint_2"
},
{
"children": [
2
],
"name": "Armature"
}
So node 0 is the parent of node 1 and node 21. However the skin in node 1 has it's joints starting at node 2. i.e. the skin in node 1 is the "parent" of the skeleton defined by the nodes from 2 to 21.
The question is then, should the transformation in node 0 be applied twice to the nodes in the skin?

Answer 1

From glTF Specifications — Skins...
Client implementations should apply only the transform of the skeleton root node to the skinned mesh while ignoring the transform of the skinned mesh node.
So in this sample, the inherited world transform of Node 1 is not applied to the joints/bones of the skin. In other words, the node-skin relationship does not apply any transformation to the joints of the skin.