# Beam Shape
# ==========

# The default directional lights are infinitely distant point sources, for which
# the only geometric customization option is the choice of beam direction defined
# by the light's position and focal point. Positional lights, however, have more
# options for beam customization.
# Consider two hemispheres:
import pyvista as pv

pl = pv.Plotter()

hemi = pv.Sphere().clip()
hemi.translate((-1, 0, 0), inplace=True)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

hemi = hemi.rotate_z(180, inplace=False)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

pl.show()

# We can see that the default lighting does a very good job of articulating the
# shape of the hemispheres.
# Let's shine a directional light on them, positioned between the hemispheres and
# oriented along their centers:
pl = pv.Plotter(lighting='none')

hemi = pv.Sphere().clip()
hemi.translate((-1, 0, 0), inplace=True)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

hemi = hemi.rotate_z(180, inplace=False)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

light = pv.Light(position=(0, 0, 0), focal_point=(-1, 0, 0))
pl.add_light(light)

pl.show()

# Both hemispheres have their surface lit on the side that faces the light.
# This is consistent with the point source positioned at infinity, directed from
# the light's nominal position toward the focal point.
# Now let's change the light to a positional light (but not a spotlight):
pl = pv.Plotter(lighting='none')

hemi = pv.Sphere().clip()
hemi.translate((-1, 0, 0), inplace=True)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

hemi = hemi.rotate_z(180, inplace=False)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

light = pv.Light(position=(0, 0, 0), focal_point=(-1, 0, 0))
light.positional = True
light.cone_angle = 90
pl.add_light(light)

pl.show()

# Now the inner surface of both hemispheres is lit. A positional light with a
# cone angle of 90 degrees (or more) acts as a point source located at the
# light's nominal position. It could still display attenuation, see the
# Attenuation example.
# Switching to a spotlight (i.e. a positional light with a cone angle less
# than 90 degrees) will enable beam shaping using the `pyvista.Light.exponent`
# property. Let's put our hemispheres side by side for this, and put a light in
# the center of each: one spotlight, one merely positional.
pl = pv.Plotter(lighting='none')

hemi = pv.Sphere().clip()
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

offset = 1.5
hemi = hemi.translate((0, offset, 0), inplace=False)
pl.add_mesh(hemi, color='cyan', smooth_shading=True)

# non-spot positional light in the center of the first hemisphere
light = pv.Light(position=(0, 0, 0), focal_point=(-1, 0, 0))
light.positional = True
light.cone_angle = 90
# add attenuation to reduce cross-talk between the lights
light.attenuation_values = (0, 0, 2)
pl.add_light(light)

# spotlight in the center of the second hemisphere
light = pv.Light(position=(0, offset, 0), focal_point=(-1, offset, 0))
light.positional = True
light.cone_angle = 89.9
# add attenuation to reduce cross-talk between the lights
light.attenuation_values = (0, 0, 2)
pl.add_light(light)

pl.show()

# Even though the two lights only differ by a fraction of a degree in cone angle,
# the beam shaping effect enabled for spotlights causes a marked difference in
# the result.
# Once we have a spotlight we can change its `pyvista.Light.exponent`
# to make the beam shape sharper or broader. Three spotlights with varying
# sharpness:
pl = pv.Plotter(lighting='none')
hemi_template = pv.Sphere().clip()

centers = [(0, 0, 0), (0, 1.5, 0), (0, 1.5 * 0.5, 1.5 * 3**0.5 / 2)]
exponents = [1, 0.3, 5]

for center, exponent in zip(centers, exponents, strict=True):
    hemi = hemi_template.copy()
    hemi.translate(center, inplace=True)
    pl.add_mesh(hemi, color='cyan', smooth_shading=True)

    # spotlight in the center of the hemisphere, shining into it
    focal_point = center[0] - 1, center[1], center[2]
    light = pv.Light(position=center, focal_point=focal_point)
    light.positional = True
    light.cone_angle = 89.9
    light.exponent = exponent
    # add attenuation to reduce cross-talk between the lights
    light.attenuation_values = (0, 0, 2)
    pl.add_light(light)

pl.show()

# The spotlight with exponent 0.3 is practically uniform, and the one with
# exponent 5 is visibly focused along the axis of the light.

# ----------------------------------------------------------------------
# Generated by sphinx-examples-as-code https://github.com/pyvista/sphinx-examples-as-code