.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "examples/regions.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

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

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

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

.. _sphx_glr_examples_regions.py:


Regions
~~~~~~~~~~~~

Example of using TetGen to create a tetrahedral mesh with regions.

.. GENERATED FROM PYTHON SOURCE LINES 8-80



.. image-sg:: /examples/images/sphx_glr_regions_001.png
   :alt: regions
   :srcset: /examples/images/sphx_glr_regions_001.png
   :class: sphx-glr-single-img





.. code-block:: Python


    import numpy as np
    import pyvista as pv
    import tetgen

    # we create a box of air with two spheres inside it
    r = 0.1  # 100mm, radius of the spheres
    L = 0.5  # 500mm, distance of centers
    # this would give a capacitance of around 6.99pF between the two spheres

    # create geometries
    airbox = pv.Cube(center=[0, 0, 0], x_length=3 * L, y_length=L, z_length=L).triangulate()
    sphere1 = pv.Sphere(theta_resolution=16, phi_resolution=16, center=[-L / 2, 0, 0], radius=r)
    sphere2 = pv.Sphere(theta_resolution=16, phi_resolution=16, center=[L / 2, 0, 0], radius=r)

    # merge the geometries
    mesh = pv.merge([sphere1, sphere2, airbox])

    # create a plotter
    plotter = pv.Plotter(shape=(1, 2))

    # plot the input mesh
    plotter.add_mesh(mesh, show_edges=True, opacity=0.5, label="Input Mesh")
    plotter.add_text("Input Mesh", font_size=10)

    # create a subplot for the tetrahedralized mesh
    plotter.subplot(0, 1)
    plotter.add_text("Tetrahedralized Mesh", font_size=10)

    # tetrahedralize the mesh using TetGen
    tgen = tetgen.TetGen(mesh)

    # add regions to the TetGen object
    V_sphere = 4 / 3 * np.pi * r**3
    tgen.add_region(100, [-L / 2, 0, 0], V_sphere / 5000)  # sphere 1
    tgen.add_region(200, [L / 2, 0, 0], V_sphere / 5000)  # sphere 2
    tgen.add_region(300, [L * 1.5, 0, 0], V_sphere / 100)  # airbox

    # tetrahedralize the mesh with specified switches
    nodes, elem, attrib = tgen.tetrahedralize(switches="pzq1.4Aa")

    grid = tgen.grid

    # retrieve the region IDs from the attributes
    regions = np.unique(attrib[:, 0])

    # plot regions with different colors and opacities
    for reg_id in regions:
        name = f"Region {reg_id}"
        reg_mask = attrib[:, 0] == reg_id
        subgrid = grid.extract_cells(reg_mask)

        if reg_id == 100:
            color = "red"
        elif reg_id == 200:
            color = "blue"
        else:
            color = "white"

        if reg_id < 300:
            opacity = 1.0
        else:
            opacity = 0.25

        plotter.add_mesh(subgrid, show_edges=True, color=color, opacity=opacity, label=name)


    plotter.add_legend()
    plotter.link_views()

    # finally show the results
    plotter.show()


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

   **Total running time of the script:** (0 minutes 1.538 seconds)


.. _sphx_glr_download_examples_regions.py:

.. only:: html

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

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

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

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

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

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

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


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_