MeshVertexNormalListSetNormal Method (Int32, Single, Single, Single)
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, float x, float y, float z )
Public Function SetNormal ( index As Integer, x As Single, y As Single, z As Single ) As Boolean