"""
.. _plotter_lighting_example:

Plotter Lighting Systems
~~~~~~~~~~~~~~~~~~~~~~~~

The :class:`pyvista.Plotter` class comes with three options for the default
lighting system:

  * a light kit consisting of a headlight and four camera lights,
  * an illumination system containing three lights arranged around the camera,
  * no lighting.

With meshes that don't have depth information encoded in their color the
importance of an appropriate lighting setup becomes paramount for accurate
visualization.

Light kit
=========

The default ``lighting='light kit'`` option recreates a lighting setup that
corresponds to a :vtk:`vtkLightKit`. We can check what type of lights this
lighting comprises:
"""

# sphinx_gallery_thumbnail_number = 3
import pyvista as pv
from pyvista import examples

# default: light kit
pl = pv.Plotter()
light_types = [light.light_type for light in pl.renderer.lights]

# Remove from plotters so output is not produced in docs
pv.plotting.plotter._ALL_PLOTTERS.clear()

light_types


# %%
# Add a white terrain to the scene:

mesh = examples.download_st_helens().warp_by_scalar()
pl = pv.Plotter()
pl.add_mesh(mesh, color='white')
pl.show()


# %%
# Three-lights illumination
# =========================
#
# Switching to three-lights illumination gives a different character to the
# figure, in this case showing less contrast when viewing the mountain from
# the top, but having more contrast with views closer to the side. This becomes
# especially clear when exploring the figures interactively.

pl = pv.Plotter(lighting='three lights')
pl.add_mesh(mesh, color='white')
pl.show()

# %%
# Again we can check what kind of lights this setting uses:

pl = pv.Plotter(lighting='three lights')
light_types = [light.light_type for light in pl.renderer.lights]

# Remove from plotters so output is not produced in docs
pv.plotting.plotter._ALL_PLOTTERS.clear()

light_types


# %%
# Custom lighting
# ===============
#
# We can introduce our own lighting from scratch by disabling any
# lighting on plotter initialization. Adding a single scene light to a
# scene will often result in ominous visuals due to objects having
# larger regions in shadow.

pl = pv.Plotter(lighting='none', window_size=(1000, 1000))
pl.add_mesh(mesh, color='white', smooth_shading=True)
light = pv.Light()
light.set_direction_angle(30, -20)
pl.add_light(light)
pl.show()


# %%
# Custom lighting with shadows
# ============================
#
# Here, we ``enable_shadows`` to enhance the effect that the lighting
# angle has.  It has a subtle, but realistic effect.  Notice the sharp
# shadows due to the mountaintop.

pl = pv.Plotter(lighting='none', window_size=(1000, 1000))
pl.add_mesh(mesh, color='white', smooth_shading=True)
light = pv.Light()
light.set_direction_angle(20, -20)
pl.add_light(light)
pl.enable_shadows()
pl.show()
# %%
# .. tags:: lights
