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

.. only:: html

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

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

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

.. _sphx_glr_example_gallery_auto_examples_basic_point_cell_mapping.py:


Transfer data between points and cells
======================================

This tutorial starts with a point field, maps it to cells with a mean
reduction, then maps it back to points. It is the shortest introduction to the
point/cell mapping helpers in ``mesh.topology``.

.. GENERATED FROM PYTHON SOURCE LINES 11-13

Imports
-------

.. GENERATED FROM PYTHON SOURCE LINES 13-19

.. code-block:: Python

    import numpy as np
    import pyvista as pv

    import graphlow









.. GENERATED FROM PYTHON SOURCE LINES 20-22

Step 1: Build a small volume mesh
---------------------------------

.. GENERATED FROM PYTHON SOURCE LINES 22-33

.. code-block:: Python

    def make_volume_grid() -> pv.UnstructuredGrid:
        """Create a small warped hexahedral grid."""
        x = np.array([0.0, 1.0, 2.2, 3.5], dtype=np.float32)
        y = np.array([0.0, 0.8, 1.7], dtype=np.float32)
        z = np.array([0.0, 0.6, 1.4], dtype=np.float32)
        X, Y, Z = np.meshgrid(x, y, z, indexing="ij")
        Z = Z + 0.12 * X * Y
        grid = pv.StructuredGrid(X, Y, Z)
        return grid.cast_to_unstructured_grid()









.. GENERATED FROM PYTHON SOURCE LINES 34-36

Step 2: Map a point field to cells and back
-------------------------------------------

.. GENERATED FROM PYTHON SOURCE LINES 36-90

.. code-block:: Python

    def main() -> None:
        """Run the tutorial."""
        mesh = graphlow.from_pyvista(make_volume_grid(), backend="torch")

        point_field = (
            mesh.points[:, [0]]
            + 2.0 * mesh.points[:, [1]]
            - 0.5 * mesh.points[:, [2]]
        )
        cell_field = mesh.topology.map_point_to_cell(
            point_field, mode="mean", method="segment"
        )
        smoothed_point_field = mesh.topology.map_cell_to_point(
            cell_field, mode="mean", method="segment"
        )

        print(f"Point field shape: {tuple(point_field.shape)}")
        print(f"Mapped cell field shape: {tuple(cell_field.shape)}")
        print(f"Mapped-back point field shape: {tuple(smoothed_point_field.shape)}")
        print(f"First five point values: {point_field[:5, 0].tolist()}")
        print(
            "First five mapped-back point values: "
            f"{smoothed_point_field[:5, 0].tolist()}"
        )

        mesh.point_data["point_field"] = point_field
        mesh.cell_data["cell_field"] = cell_field
        mesh.point_data["smoothed_point_field"] = smoothed_point_field
        mesh.copy_features_to_pyvista()

        plotter = pv.Plotter(shape=(1, 3), window_size=[1500, 450])
        plotter.subplot(0, 0)
        plotter.add_text("Point field", font_size=12)
        plotter.add_mesh(mesh.pvmesh, scalars="point_field", show_edges=True)

        plotter.subplot(0, 1)
        plotter.add_text("Cell field", font_size=12)
        plotter.add_mesh(mesh.pvmesh, scalars="cell_field", show_edges=True)

        plotter.subplot(0, 2)
        plotter.add_text("Point field after cell mean", font_size=12)
        plotter.add_mesh(
            mesh.pvmesh,
            scalars="smoothed_point_field",
            show_edges=True,
        )

        plotter.link_views()
        plotter.camera_position = "iso"
        plotter.show()


    if __name__ == "__main__":
        main()



.. image-sg:: /example_gallery/auto_examples/basic/images/sphx_glr_point_cell_mapping_001.png
   :alt: point cell mapping
   :srcset: /example_gallery/auto_examples/basic/images/sphx_glr_point_cell_mapping_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Point field shape: (36, 1)
    Mapped cell field shape: (12, 1)
    Mapped-back point field shape: (36, 1)
    First five point values: [0.0, 1.0, 2.200000047683716, 3.5, 1.600000023841858]
    First five mapped-back point values: [1.1379998922348022, 1.674799919128418, 2.8215999603271484, 3.4316000938415527, 1.975250005722046]





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

   **Total running time of the script:** (0 minutes 0.518 seconds)


.. _sphx_glr_download_example_gallery_auto_examples_basic_point_cell_mapping.py:

.. only:: html

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

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

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

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

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

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

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


.. only:: html

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

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