|MeshVertexListSetVertex Method (Int32, Point3d)|
If [index] is less than [Count], the existing vertex at [index] will be modified.
If [index] equals [Count], a new vertex is appended to the end of the vertex list.
If [index] is larger than [Count], the function will return false.
public bool SetVertex( int index, Point3d vertex )
Public Function SetVertex ( index As Integer, vertex As Point3d ) As Boolean