.. auto-generated by dev_tools.docs.nxdl from the NXDL source base_classes/NXcg_alpha_complex.nxdl.xml -- DO NOT EDIT

.. index::
    ! NXcg_alpha_complex (base class)
    ! cg_alpha_complex (base class)
    see: cg_alpha_complex (base class); NXcg_alpha_complex

.. _NXcg_alpha_complex:

==================
NXcg_alpha_complex
==================

**Status**:

  base class, extends :ref:`NXcg_primitive`

**Description**:

  .. collapse:: Computational geometry of alpha complexes (alpha shapes or alpha wrappings) abou ...

      Computational geometry of alpha complexes (alpha shapes or alpha wrappings) about primitives.

      For details see:

      * https://dx.doi.org/10.1109/TIT.1983.1056714 for 2D,
      * https://dx.doi.org/10.1145/174462.156635 for 3D,
      * https://dl.acm.org/doi/10.5555/871114 for weighted, and
      * https://doc.cgal.org/latest/Alpha_shapes_3 for 3D implementation of alpha shapes, and
      * https://doc.cgal.org/latest/Manual/packages.html#PkgAlphaWrap3 for 3D alpha wrappings

      in CGAL, the Computational Geometry Algorithms Library respectively.
      As a starting point, we follow the conventions of the CGAL library.

      In general, an alpha complex is a not necessarily connected or not necessarily pure complex,
      i.e. singular faces may exist. The number of cells, faces, and edges depends on how a specific
      alpha complex is filtered for lower-dimensional simplices. The fields is_regularized and
      regularization can be used to provide details about regularization procedures.

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXcg_point`, :ref:`NXcg_tetrahedron`, :ref:`NXcg_triangle`

.. index:: NXcg_point (base class); used in base class, NXcg_triangle (base class); used in base class, NXcg_tetrahedron (base class); used in base class

**Structure**:

  .. _/NXcg_alpha_complex/type-field:

  .. index:: type (field)

  **type**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Type of alpha complex following the terminology used by CGAL for now. ...

        Type of alpha complex following the terminology used by CGAL for now.

        Alpha_shape means meshes created using one of the alpha_shape algorithm.
        Alpha_wrapping means meshes created using the alpha_wrapping algorithm.

        Any of these values: ``convex_hull`` | ``alpha_shape`` | ``alpha_wrapping``

  .. _/NXcg_alpha_complex/regularization-field:

  .. index:: regularization (field)

  **regularization**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Human-readable description about regularization procedures.

  .. _/NXcg_alpha_complex/is_regularized-field:

  .. index:: is_regularized (field)

  **is_regularized**: (optional) :ref:`NX_BOOLEAN <NX_BOOLEAN>` 

    Was the alpha complex regularized, i.e. have singular faces been removed, or not.

  .. _/NXcg_alpha_complex/alpha-field:

  .. index:: alpha (field)

  **alpha**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_ANY <NX_ANY>`} 

    .. collapse:: The alpha parameter, i.e. the squared radius of the alpha-sphere ...

        The alpha parameter, i.e. the squared radius of the alpha-sphere
        that is used when computing the alpha complex.

  .. _/NXcg_alpha_complex/offset-field:

  .. index:: offset (field)

  **offset**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`} 

    The offset distance parameter used when computing alpha_wrappings.

  .. _/NXcg_alpha_complex/CG_POINT-group:

  :bolditalic:`CG_POINT`: (optional) :ref:`NXcg_point` 

    Point cloud serving as input for the computation of the alpha complex.

  .. _/NXcg_alpha_complex/TRIANGLE_SOUP-group:

  :bolditalic:`TRIANGLE_SOUP`: (optional) :ref:`NXcg_triangle` 

    Triangle soup serving as input for the computation of the alpha complex.

  .. _/NXcg_alpha_complex/ALPHA_COMPLEX-group:

  :bolditalic:`ALPHA_COMPLEX`: (optional) :ref:`NXcg_triangle` 

    Triangle mesh representing the output of the computation, i.e. the alpha complex.

  .. _/NXcg_alpha_complex/TETRAHEDRALIZATION-group:

  :bolditalic:`TETRAHEDRALIZATION`: (optional) :ref:`NXcg_tetrahedron` 

    Tetrahedra representing an interior volume of the alpha complex (if such exists).


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXcg_alpha_complex/alpha-field </NXcg_alpha_complex/alpha-field>`
* :ref:`/NXcg_alpha_complex/ALPHA_COMPLEX-group </NXcg_alpha_complex/ALPHA_COMPLEX-group>`
* :ref:`/NXcg_alpha_complex/CG_POINT-group </NXcg_alpha_complex/CG_POINT-group>`
* :ref:`/NXcg_alpha_complex/is_regularized-field </NXcg_alpha_complex/is_regularized-field>`
* :ref:`/NXcg_alpha_complex/offset-field </NXcg_alpha_complex/offset-field>`
* :ref:`/NXcg_alpha_complex/regularization-field </NXcg_alpha_complex/regularization-field>`
* :ref:`/NXcg_alpha_complex/TETRAHEDRALIZATION-group </NXcg_alpha_complex/TETRAHEDRALIZATION-group>`
* :ref:`/NXcg_alpha_complex/TRIANGLE_SOUP-group </NXcg_alpha_complex/TRIANGLE_SOUP-group>`
* :ref:`/NXcg_alpha_complex/type-field </NXcg_alpha_complex/type-field>`

**NXDL Source**:
  https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/base_classes/NXcg_alpha_complex.nxdl.xml