anchor.diff:        
      ! PolyData (.vtp)  Serial vtkPolyData (unstructured)
      CALL GetNewUnit( Un, ErrStat2, ErrMsg2 )      
  -   CALL OpenFOutFile ( Un, TRIM(FileRootName)//'.Reference.vtp', ErrStat, ErrMsg )
  +   CALL OpenFOutFile ( Un, TRIM(FileRootName)//'_Reference.vtp', ErrStat, ErrMsg )
         IF ( ErrStat >= AbortErrLev ) RETURN
               
         WRITE(Un,'(A)')         '<?xml version="1.0"?>'            
  
positive.code: !**********************************************************************************************************************************
  ! LICENSING
  ! Copyright (C) 2013-2015  National Renewable Energy Laboratory
  !
  !    This file is part of the NWTC Subroutine Library.
  !
  
negative.code: !----------------------------------------------------------------------------------------------------------------------------------
  !> This routine writes mesh information in VTK format.
  !! see VTK file information format for XML, here: http://www.vtk.org/wp-content/uploads/2015/04/file-formats.pdf
  SUBROUTINE MeshWrVTK ( M, FileRootName, VTKcount, ErrStat, ErrMsg, Sib, PositionOnly )
        
     TYPE(MeshType),  INTENT(IN)           :: M             !< mesh to be written
     CHARACTER(*),    INTENT(IN)           :: FileRootName  !< Name of the file to write the output in (excluding extension)
     INTEGER(IntKi),  INTENT(IN)           :: VTKcount      !< Indicates number for VTK output file (when 0, the routine will also write reference information)
     INTEGER(IntKi),  INTENT(OUT)          :: ErrStat       !< Indicates whether an error occurred (see NWTC_Library)
     CHARACTER(*),    INTENT(OUT)          :: ErrMsg        !< Error message associated with the ErrStat
  
     TYPE(MeshType),  INTENT(IN), OPTIONAL :: Sib           !< "functional" Sibling of M that contains translational displacement information (used to place forces at displaced positions) 
                                                            !! (note that I don't check that Sib%TranslationDisp exists before using it, so make sure it's there and has at least as many nodes as M!)
     LOGICAL,         INTENT(IN), OPTIONAL :: PositionOnly  !< flag to determine if we want to output any fields or just the absolute position of this mesh
  
     ! local variables
     INTEGER(IntKi)                        :: Un            ! fortran unit number
     INTEGER(IntKi)                        :: i,j           ! loop counters
     CHARACTER(1024)                       :: FileName
     LOGICAL                               :: OnlyPosition
        
     INTEGER(IntKi)                        :: ErrStat2 
     CHARACTER(ErrMsgLen)                  :: ErrMsg2
  