Visualize geometry
==================

.. include:: ../shared.rst

.. _vdb_view:

In `vdb\_view`
--------------

:bash:`vdb_view` is a third-party software, which can be found in the `libopenvdb-tools` package. You can search for detailed usage online.  
:bash:`vdb_view` is a command line utility

.. code:: bash

  > vdb_view geometry.vdb 

The grid is shown at the start

.. image:: ../images/vdb_view1.png
   :height: 400px

To see geometry press '1' (toggle tree topology view off) and '2' (toggle surface view on) keys on your keyboard.

.. image:: ../images/vdb_view2.png
   :height: 400px

Navigate with mouse

.. _blender:
In Blender
----------

Download Blender (free software) from `the official website <https://www.blender.org/>`_.

Version 3.1 and above can be used.

Open Blender graphical interface. 

Click 
:menuselection:`Add --> Volume --> Import OpenVDB`, select the :file:`geometry.vdb` file. 

.. image:: ../images/blender1.png
   :height: 400px

Select the initial cube with left mouse click.  

On the panel on the bottom right, select :menuselection:`Modifiers` tab.
Click :menuselection:`Add Modifier --> Generate --> Volume to Mesh`

.. image:: ../images/blender2.png
   :height: 400px

In the Modifier settings, fill in

 * `Object : geometry`
 * `Grid Name : FillingFrac`
 * `Threshold : 0.5`

This will plot the isosurface where ``FillingFrac``:math:`=0.5`. 

The ``FillingFrac`` grid is filled with scalar values of :math:`\varphi`, that is, filling fraction. 
:math:`\varphi=1` in the mesh cells filled with solid or liquid, and :math:`\varphi=0` in the empty cells. 
Some cells are partially filled. The isosurface where :math:`\varphi=0.5` is a good approximation of the metal surface.  


.. image:: ../images/blender3.png
   :height: 400px

Navigate Viewport with :kbd:`[Numpad .]`, Middle Mouse, Middle Mouse + Shift, Middle Mouse + Ctrl.


.. image:: ../images/blender4.png
   :height: 400px