.. _loading:

================
Loading Geometry
================

Generally, a reader class is provided for each format. The reader is created, then told to
load a file, and it creates a Registry object (see :ref:`introduction-registry`) containing
the model. The registry is the final object from a reader, and its top-most volume can be
used for visualisation or other operations.

.. tabs::

   .. tab:: GDML

      In directory :code:`pyg4ometry/test/gdmlG4examples/ChargeExchangeMC/`

      .. code-block:: python
	    :linenos:

	    import pyg4ometry
	    r = pyg4ometry.gdml.Reader("lht.gdml")
	    l = r.getRegistry().getWorldVolume()
	    v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
	    v.addLogicalVolume(l)
	    v.view()

      .. figure:: figures/viewing-gdml.png
		  :width: 80%
		  :align: center

		  Geant4 example GDML from ChargeExchangeMC example.

   .. tab:: FLUKA

      In directory :code:`pyg4ometry/test/flukaCompoundExamples`

      **Note** FLUKA geometry can be loaded but cannot be visualised directly without
      conversion to a Geant4 model. This is not necessary for loading, but shown here.

      .. code-block:: python
	    :linenos:
	       
	    import pyg4ometry
	    r = pyg4ometry.fluka.Reader("corrector-dipole2.inp")
	    flukaRegistry = r.flukaregistry

	    geantRegistry = pyg4ometry.convert.fluka2Geant4(flukaRegistry)
	    
	    l = geantRegsitry.getWorldVolume()
	    v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
	    v.addLogicalVolume(l)
	    v.view()

      .. figure:: figures/viewing-fluka.png
		  :width: 80%
		  :align: center

		  FLUKA example of a dipole magnet.

   .. tab:: ROOT

      In directory :code:`pyg4ometry/test/root2Gdml`
	    
      .. code-block:: python
	    :linenos:

	    import pyg4ometry
	    r = pyg4ometry.io.ROOTTGeo.Reader("example_lht.root")
	    l = r.getRegistry().getWorldVolume()
	    v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
	    v.addLogicalVolume(l)
	    v.view()

      .. figure:: figures/viewing-root.png
		  :width: 80%
		  :align: center

		  ROOT example of Geant4's LHT geometry.

   
   .. tab:: STL

      In directory :code:`pyg4ometry/test/stl`

      STL files are typically used for a single watertight solid mesh. This mesh is
      converted to a TesselatedSolid and then a logical volume which can be placed
      in a geometry. In directory :code:`pyg4ometry/test/stl`.

      .. code-block:: python

	    import pyg4ometry
	    reg = pyg4ometry.geant4.Registry()
	    r = pyg4ometry.stl.Reader("utahteapot.stl", reg)
	    s = r.getSolid()
	    copper = pyg4ometry.geant4.MaterialPredefined("G4_Cu", reg)
	    l = pyg4ometry.geant4.LogicalVolume(s, copper, "utahteapot_lv", reg)
	    v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
	    v.addLogicalVolume(l)
	    v.view()

      .. figure:: tutorials/tutorial2.png
	 :alt: Example of STL loading in pyg4ometry

   
   .. tab:: STEP


      In directory :code:`pyg4ometry/test/freecad`

      .. code-block:: python
	    :linenos:

	    import pyg4ometry
	    r  = pyg4ometry.freecad.Reader("08_AshTray.step")
	    r.relabelModel()
	    r.convertFlat()
	    l = r.getRegistry().getWorldVolume()
	    v = pyg4ometry.visualisation.VtkViewer()
	    v.addLogicalVolume(l)
	    v.view()

      .. figure:: tutorials/tutorial3.png
		  :alt: Example of STEP loading in pyg4ometry