Visualization Tutorial — Droplet Surface and Contact Angle
===========================================================

This tutorial demonstrates how to visualize a droplet and compute its contact angle using the **wetting_angle_kit** package. We'll use the ``sliced`` contact angle method and visualize the resulting droplet with the ``DropletSlicedPlotter`` class.

----

1. Overview
-----------

The visualization workflow involves the following steps:

1. Parse atomic positions from a trajectory file.
2. Identify water molecules (oxygen and hydrogen atoms).
3. Compute the droplet surface and contact angle using the *sliced method*.
4. Visualize the droplet, fitted circle, tangent, and wall.

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2. Import Required Modules
---------------------------

.. code-block:: python

   import numpy as np
   from wetting_angle_kit.parser import (
       DumpParser,
       DumpWaterMoleculeFinder,
       DumpWallParser,
   )
   from wetting_angle_kit.contact_angle_method.sliced_method import ContactAngleSliced
   from wetting_angle_kit.visualization_angles import DropletSlicedPlotter

----

3. Define the Input Trajectory
-------------------------------

.. code-block:: python

   filename = (
       "../wetting_angle_kit/tests/trajectories/traj_10_3_330w_nve_4k_reajust.lammpstrj"
   )

----

4. Identify Water Molecules
----------------------------

.. code-block:: python

   wat_find = DumpWaterMoleculeFinder(
       filename, particle_type_wall={3}, oxygen_type=1, hydrogen_type=2
   )

   oxygen_indices = wat_find.get_water_oxygen_ids(frame_index=0)
   print("Number of water molecules detected:", len(oxygen_indices))

----

5. Parse Atomic Coordinates
----------------------------

.. code-block:: python

   parser = DumpParser(filepath=filename)
   oxygen_position = parser.parse(frame_index=10, indices=oxygen_indices)

   coord_wall = DumpWallParser(filename, particule_liquid_type={1, 2})
   wall_coords = coord_wall.parse(frame_index=1)

----

6. Compute Contact Angles
--------------------------

.. code-block:: python

   processor = ContactAngleSliced(
       liquid_coordinates=oxygen_position,
       liquid_geom_center=np.mean(oxygen_position, axis=0),
       droplet_geometry="cylinder_y",
       delta_cylinder=5,
       max_dist=100,
       width_cylinder=21,
   )

   list_alfas, array_surfaces, array_popt = processor.predict_contact_angle()
   print("Mean contact angles (°):", list_alfas)

----

7. Visualize the Droplet
-------------------------

.. code-block:: python

   plotter = DropletSlicedPlotter(center=True, show_wall=True, molecule_view=True)

   plotter.plot_surface_points(
       oxygen_position=oxygen_position,
       surface_data=array_surfaces,
       popt=array_popt[0],
       wall_coords=wall_coords,
       output_filename="droplet_plot.png",
       alpha=list_alfas[0],
   )

   print(" Plot saved as 'droplet_plot.png'")

Outputs
-------

.. image:: ../../images/droplet_plot.png
   :alt: Droplet sliced method visualization