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Skinning influenced by more than 4 joints #1381

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Nov 14, 2018
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Skinning influenced by more than 4 joints #1381

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21df3a2
Skinning influenced by more than 4 joints
broughtong Jul 6, 2018
ca2dc6f
Added note about only requiring a single set
broughtong Jul 19, 2018
9f95914
Merge branch 'master' into many-joints
broughtong Jul 24, 2018
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4 changes: 3 additions & 1 deletion specification/2.0/README.md
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Expand Up @@ -913,13 +913,15 @@ The mesh for a skin is defined with vertex attributes that are used in skinning
}
```

The number of joints that influence one vertex is limited to 4, so referenced accessors must have `VEC4` type and following component formats:
The number of joints that influence one vertex is limited to 4 per set, so referenced accessors must have `VEC4` type and following component formats:

* **`JOINTS_0`**: `UNSIGNED_BYTE` or `UNSIGNED_SHORT`
* **`WEIGHTS_0`**: `FLOAT`, or normalized `UNSIGNED_BYTE`, or normalized `UNSIGNED_SHORT`

The joint weights for each vertex must be >= 0, and normalized to have a linear sum of one. No joint may have more than one non-zero weight for a given vertex.

In the event that of any of the vertices are influenced by more than four joints, the additional joint and weight information will be found in subsequent sets. For example `JOINTS_1` and `WEIGHTS_1` if present will reference the accessor for up to 4 additional joints that influence the vertices. Note that client implementations are only required to support a single set of up to four weights and joints, however not supporting all weight and joint sets present in the file may have an impact on the model's animation.

#### Joint Hierarchy

The joint hierarchy used for controlling skinned mesh pose is simply the glTF node hierarchy, with each node designated as a joint. The following example defines a joint hierarchy of two joints.
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