| mesh | 静态网格，将接收蒙皮网格的快照。 |
创建 SkinnedMeshRenderer 的快照并将其存储在 mesh 中。
这些顶点相对于 SkinnedMeshRenderer 变换组件。
Notes:
The snapshot is still computed even when updateWhenOffscreen is set to false and the skinned mesh object is currently offscreen.
When this function is called the skinning process will always take place on the CPU, regardless of the GPU Skinning setting