ExportToVTK

Exports an AbstractMesh_ object to a VTK file format, which can be visualized in applications like ParaView or VisIt.

Interface

INTERFACE
  MODULE SUBROUTINE ExportToVTK(obj, vtk, nodeCoord, filename, &
                                opentag, content, closetag)
    CLASS(AbstractMesh_), INTENT(IN) :: obj
    TYPE(VTKFile_), INTENT(INOUT) :: vtk
    REAL(DFP), OPTIONAL, INTENT(IN) :: nodeCoord(:, :)
    CHARACTER(*), OPTIONAL, INTENT(IN) :: filename
    LOGICAL(LGT), OPTIONAL, INTENT(IN) :: opentag
    !! Default is true
    LOGICAL(LGT), OPTIONAL, INTENT(IN) :: closetag
    !! Default is true
    LOGICAL(LGT), OPTIONAL, INTENT(IN) :: content
    !! Default is true
  END SUBROUTINE ExportToVTK
END INTERFACE

Arguments

Argument	Intent	Type	Description
obj	IN	CLASS(AbstractMesh_)	The AbstractMesh_ object to be exported
vtk	INOUT	TYPE(VTKFile_)	VTK file handler for writing the mesh data
nodeCoord	OPTIONAL, IN	REAL(DFP) (:,:)	Node coordinates array with shape [3, nPoints]
filename	OPTIONAL, IN	CHARACTER(*)	Output filename when creating a new VTK file
opentag	OPTIONAL, IN	LOGICAL(LGT)	Whether to open VTK piece tags (default: TRUE)
closetag	OPTIONAL, IN	LOGICAL(LGT)	Whether to close VTK piece tags (default: TRUE)
content	OPTIONAL, IN	LOGICAL(LGT)	Whether to write mesh cell data (default: TRUE)

Description

This subroutine exports the mesh to a VTK file in the UnstructuredGrid format. It performs the following operations:

1. If the VTK file is not already initialized, it creates a new one using the provided filename
2. Writes the piece information if opentag is true
3. Writes the node coordinates (points):
   • Uses provided nodeCoord if present
   • Otherwise extracts coordinates from the mesh
4. If content is true, writes cell connectivity data including:
   • Connectivity information
   • Offsets for each cell
   • Cell types in VTK format
5. Closes the piece and VTK file if closetag is true

Implementation Details

• Uses binary appended VTK format for efficient file size
• Converts mesh element types to VTK-compatible element types
• Handles local-to-global node number mapping
• Only writes data for active elements in the mesh
• Properly handles different element topologies

Usage Example

TYPE(FEMesh_) :: mesh
TYPE(VTKFile_) :: vtk
CHARACTER(*), PARAMETER :: filename = "mesh.vtk"

! Read mesh from HDF5 file
CALL mesh%IMPORT(hdf5file, "/meshGroup")

! Export to VTK
CALL mesh%ExportToVTK(vtk=vtk, filename=filename)

Notes

• If the vtk object is already initialized, it will use the existing file
• If nodeCoord is not provided, the method will extract coordinates from the mesh
• The VTK file format is compatible with visualization tools like ParaView and VisIt
• Elements are only exported if they are active (isElementActive returns true)