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.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_auto_examples_howto_preprocessing_plot_terrain_meshing.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_examples_howto_preprocessing_plot_terrain_meshing.py:


Terrain meshing
===============

.. sectionauthor:: Dominik Kern (TU Bergakademie Freiberg)

.. GENERATED FROM PYTHON SOURCE LINES 10-12

.. code-block:: Python
   :dedent: 1










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Here we show different tools to mesh a minimum example of a terrain, given by
raster data. These are:

* `Gmsh <http://gmsh.info>`_
* `OGS Utilities <https://www.opengeosys.org/docs/tools/getting-started/overview/>`_
* `PyVista <https://docs.pyvista.org/index.html>`_
* `TetGen <https://wias-berlin.de/software/index.jsp?id=TetGen&lang=1>`_

.. image:: ../../examples/howto_preprocessing/terrain_meshing/terrain.png


.. GENERATED FROM PYTHON SOURCE LINES 30-55

Gmsh
----

If the relief is given as relief.grd, then we need to convert it first
(file names are hard coded):

.. code-block:: python

   python -m ogstools.examples.mesh_terrain.grd2stl

Running:

.. code-block:: python

   python -m ogstools.examples.mesh_terrain.pyvista_mesh

reads in `relief.stl` and meshes the volume between the relief and a
*z*-coordinate specified in the script. In addition it creates physical
groups for all bounding surfaces.

.. image:: ../../examples/howto_preprocessing/terrain_meshing/gmsh.png

.. literalinclude:: ../../../ogstools/examples/mesh_terrain/gmsh_mesh.py
  :language: python


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OGS Utilities
-------------

OGS comes with some utilities for meshing. Required are raster files
(`.grd`) and a file specifying their sequence (here `layer_file_list`).
The following commands create a 2D mesh, extrude it to 3D-wedge elements and
then fit in a structured hex mesh.

.. code-block:: bash

   generateStructuredMesh -e tri --lx 10 --nx 20 --ly 10 --ny 20 -o tri2d_mesh.vtu
   createLayeredMeshFromRasters -i tri2d_mesh.vtu -o wedge3d_mesh.vtu -r layer_file_list
   Vtu2Grid -i wedge3d_mesh.vtu -o hex3d_mesh.vtu -x 0.4

.. image:: ../../examples/howto_preprocessing/terrain_meshing/ogstools.png


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PyVista
-------

PyVista is mainly made for visualization, but brings some meshing
functionality. It has a grid reader to read relief.grd and a meshio-interface
to write to relief.vtu. Running:

.. code-block:: bash

   python -m ogstools.examples.mesh_terrain.pyvista_mesh

generates a structured mesh on the relief and extrudes it downwards to 3D.

.. image:: ../../examples/howto_preprocessing/terrain_meshing/pyvista.png

.. literalinclude:: ../../../ogstools/examples/mesh_terrain/pyvista_mesh.py
  :language: python


.. GENERATED FROM PYTHON SOURCE LINES 95-107

TetGen
------

TetGen creates a 3D mesh from a 2D mesh on a closed surface.
This surface may be either read from stl-files or PyVista-data.
Currently the *pyvista-tetgen basic example* (`tetgen_example.py`)
has been prepared for terrain meshing (`tetgen_mesh.py`),
but is not finished yet.

.. literalinclude:: ../../../ogstools/examples/mesh_terrain/tetgen_mesh.py
  :language: Python



.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.000 seconds)


.. _sphx_glr_download_auto_examples_howto_preprocessing_plot_terrain_meshing.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_terrain_meshing.ipynb <plot_terrain_meshing.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_terrain_meshing.py <plot_terrain_meshing.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_terrain_meshing.zip <plot_terrain_meshing.zip>`