Point clouds
============

The vertices of meshes are contained in a reference set of points in
:math:`\mathbb{R}^{3}` (a point cloud).  Since points of
:math:`\mathbb{R}^3` are modelled by objects of type ``R3`` (which is an
alias of :doc:`smallvector` ``SmallVector<double,3>``), a point cloud is
modelled by an object of type ``Nodes`` which essentially consists in a
dynamically allocated array of objects of type ``R3``.

Point clouds are systematically composed of points of type ``R3``,
even when considering problems and meshes in :math:`\mathbb{R}^{2}`. 

Standard use-cases only involve one single instance of ``Nodes``
which is a reference point cloud used by all ``Mesh`` and ``Element``
entities.

.. doxygenclass:: Nodes
   :members: