:orphan:

.. _filters:

Filters
=======

Demonstrate the PyVista filters API to perform mesh analysis and alteration


.. note::

    This section of the tutorial was adopted from the Filtering section
    of `PyVista's Example Gallery <https://docs.pyvista.org/version/stable/examples/01-filter/index.html>`_.


PyVista mesh objects have a suite of common filters ready for immediate use
directly on the object. These filters include the following (see `Filters API
<https://docs.pyvista.org/version/stable/api/core/filters.html>`_ for a
complete list):

* `slice()`_ creates a single slice through the input dataset on a user defined plane
* `slice_orthogonal()`_: creates a :class:`pyvista.MultiBlock` dataset of three orthogonal slices
* `slice_along_axis()`_: creates a :class:`pyvista.MultiBlock` dataset of many slices along a specified axis
* `threshold()`_: Thresholds a dataset by a single value or range of values
* `threshold_percent()`_: Threshold by percentages of the scalar range
* `clip()`_: Clips the dataset by a user defined plane
* `outline_corners()`_: Outlines the corners of the data extent
* `extract_geometry()`_: Extract surface geometry

.. _slice(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.slice.html
.. _slice_orthogonal(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.slice_orthogonal.html
.. _slice_along_axis(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.slice_along_axis.html
.. _threshold(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.threshold.html
.. _threshold_percent(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.threshold_percent.html
.. _clip(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.clip.html
.. _outline_corners(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.outline_corners.html
.. _extract_geometry(): https://docs.pyvista.org/version/stable/api/core/_autosummary/pyvista.dataobjectfilters.extract_geometry.html


To use these filters, call the method of your choice directly on your data
object:

.. pyvista-plot::
   :context:
   :include-source: False

   import pyvista
   pyvista.set_plot_theme('document')
   pyvista.set_jupyter_backend('trame')
   pyvista.global_theme.axes.show = False
   pyvista.global_theme.smooth_shading = True


.. pyvista-plot::
   :context:

    import pyvista as pv
    from pyvista import examples

    dataset = examples.load_uniform()
    dataset.set_active_scalars("Spatial Point Data")

    # Apply a threshold over a data range
    threshed = dataset.threshold([100, 500])

    outline = dataset.outline()


And now there is a thresholded version of the input dataset in the new
``threshed`` object. To learn more about what keyword arguments are available to
alter how filters are executed, print the docstring for any filter attached to
PyVista objects with either ``help(dataset.threshold)`` or using ``shift+tab``
in an IPython environment.

We can now plot this filtered dataset along side an outline of the original
dataset:


.. pyvista-plot::
   :context:

    pl = pv.Plotter()
    pl.add_mesh(outline, color="k")
    pl.add_mesh(threshed)
    pl.camera_position = [-2, 5, 3]
    pl.show()



What about other filters? Let's collect a few filter results and compare them:


.. pyvista-plot::

    import pyvista as pv
    from pyvista import examples

    dataset = examples.load_uniform()
    outline = dataset.outline()
    threshed = dataset.threshold([100, 500])
    contours = dataset.contour()
    slices = dataset.slice_orthogonal()
    glyphs = dataset.glyph(factor=1e-3, geom=pv.Sphere(), orient=False)

    pl = pv.Plotter(shape=(2, 2))
    # Show the threshold
    pl.add_mesh(outline, color="k")
    pl.add_mesh(threshed, show_scalar_bar=False)
    pl.camera_position = [-2, 5, 3]
    # Show the contour
    pl.subplot(0, 1)
    pl.add_mesh(outline, color="k")
    pl.add_mesh(contours, show_scalar_bar=False)
    pl.camera_position = [-2, 5, 3]
    # Show the slices
    pl.subplot(1, 0)
    pl.add_mesh(outline, color="k")
    pl.add_mesh(slices, show_scalar_bar=False)
    pl.camera_position = [-2, 5, 3]
    # Show the glyphs
    pl.subplot(1, 1)
    pl.add_mesh(outline, color="k")
    pl.add_mesh(glyphs, show_scalar_bar=False)
    pl.camera_position = [-2, 5, 3]

    pl.link_views()
    pl.show()


Filter Pipeline
+++++++++++++++

In VTK, filters are often used in a pipeline where each algorithm passes its
output to the next filtering algorithm. In PyVista, we can mimic the
filtering pipeline through a chain; attaching each filter to the last filter.
In the following example, several filters are chained together:

1. First, and empty ``threshold`` filter to clean out any ``NaN`` values.
2. Use an ``elevation`` filter to generate scalar values corresponding to height.
3. Use the ``clip`` filter to cut the dataset in half.
4. Create three slices along each axial plane using the ``slice_orthogonal`` filter.

Apply a filtering chain

.. pyvista-plot::
   :context:

    result = dataset.threshold().elevation().clip(normal="z").slice_orthogonal()

And to view this filtered data, simply call the ``plot`` method
(``result.plot()``) or create a rendering scene:

.. pyvista-plot::
   :context:

    pl = pv.Plotter()
    pl.add_mesh(outline, color="k")
    pl.add_mesh(result, scalars="Elevation")
    pl.view_isometric()
    pl.show()


Exercises
~~~~~~~~~



.. raw:: html

    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Using common filters like thresholding and clipping.">

.. only:: html

  .. image:: /tutorial/04_filters/images/thumb/sphx_glr_a_lesson_filters_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_a_lesson_filters.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Using Common Filters</div>
    </div>


.. thumbnail-parent-div-close

.. raw:: html

    </div>


.. toctree::
   :hidden:

   /tutorial/04_filters/a_lesson_filters

Bonus Content
~~~~~~~~~~~~~



.. raw:: html

    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Video games like Minecraft use Perlin noise to create terrain.  Here, we create a voxelized mesh similar to a Minecraft &quot;cave&quot;.">

.. only:: html

  .. image:: /tutorial/04_filters/bonus/images/thumb/sphx_glr_f_sampling_functions_3d_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_bonus_f_sampling_functions_3d.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Sample Function: Perlin Noise in 3D</div>
    </div>


.. thumbnail-parent-div-close

.. raw:: html

    </div>

Do it yourself
~~~~~~~~~~~~~~



.. raw:: html

    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Clip/cut any dataset using using planes or boxes.">

.. only:: html

  .. image:: /tutorial/04_filters/exercises/images/thumb/sphx_glr_b_clipping_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_exercises_b_clipping.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Clipping with Planes & Boxes</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip=" Compute normals on a surface.">

.. only:: html

  .. image:: /tutorial/04_filters/exercises/images/thumb/sphx_glr_c_compute-normals_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_exercises_c_compute-normals.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Computing Surface Normals</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Generate iso-lines or -surfaces for the scalars of a surface or volume.">

.. only:: html

  .. image:: /tutorial/04_filters/exercises/images/thumb/sphx_glr_d_contouring_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_exercises_d_contouring.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Contouring</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Use vectors in a dataset to plot and orient glyphs/geometric objects.">

.. only:: html

  .. image:: /tutorial/04_filters/exercises/images/thumb/sphx_glr_e_glyphs_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_exercises_e_glyphs.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Plotting Glyphs (Vectors or PolyData)</div>
    </div>


.. thumbnail-parent-div-close

.. raw:: html

    </div>

Solutions
~~~~~~~~~



.. raw:: html

    <div class="sphx-glr-thumbnails">

.. thumbnail-parent-div-open

.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Clip/cut any dataset using using planes or boxes.">

.. only:: html

  .. image:: /tutorial/04_filters/solutions/images/thumb/sphx_glr_b_clipping_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_solutions_b_clipping.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Clipping with Planes & Boxes</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip=" Compute normals on a surface.">

.. only:: html

  .. image:: /tutorial/04_filters/solutions/images/thumb/sphx_glr_c_compute-normals_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_solutions_c_compute-normals.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Computing Surface Normals</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Generate iso-lines or -surfaces for the scalars of a surface or volume.">

.. only:: html

  .. image:: /tutorial/04_filters/solutions/images/thumb/sphx_glr_d_contouring_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_solutions_d_contouring.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Contouring</div>
    </div>


.. raw:: html

    <div class="sphx-glr-thumbcontainer" tooltip="Use vectors in a dataset to plot and orient glyphs/geometric objects.">

.. only:: html

  .. image:: /tutorial/04_filters/solutions/images/thumb/sphx_glr_e_glyphs_thumb.png
    :alt:

  :ref:`sphx_glr_tutorial_04_filters_solutions_e_glyphs.py`

.. raw:: html

      <div class="sphx-glr-thumbnail-title">Plotting Glyphs (Vectors or PolyData)</div>
    </div>


.. thumbnail-parent-div-close

.. raw:: html

    </div>


.. toctree::
   :hidden:
   :includehidden:


   /tutorial/04_filters//bonus/index.rst
   /tutorial/04_filters//exercises/index.rst
   /tutorial/04_filters//solutions/index.rst



.. only:: html

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

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