MeshVertexNormalListSetNormal Method (Int32, Vector3d)
If [index] is less than [Count], the existing vertex normal at [index] will be modified.
If [index] equals [Count], a new vertex normal is appended to the end of the list.
If [index] is larger than [Count], the function will return false.
public bool SetNormal( int index, Vector3d normal )
Public Function SetNormal ( index As Integer, normal As Vector3d ) As Boolean