<SYSTEM_TASK:>
Given the following text description, write Python code to implement the functionality described below step by step
<END_TASK>
<USER_TASK:>
Description:
 Lightning
By default ipyvolume uses a fake lighting model that works ok for depth perception. To get more realistic lighting effects ipyvolume supports a few light models from pythreejs/threejs.
Step1:  Ambient light
For global illumination, which will not cast shadows
Step2:  Hemisphere light
A light source positioned directly above the scene, with color fading from the sky color to the ground color.
This light cannot be used to cast shadows.
Step3:  Directional light
A Directional Light source illuminates all objects equally from a given direction. This light can be used to cast shadows. The light is recommended together with hemisphere.
Step4:  Spot light
A Spot Light produces a directed cone of light. The light becomes more intense closer to the spotlight source and to the center of the light cone. This light can be used to cast shadows.
Step5:  Point light
A Point Light originates from a single point and spreads outward in all directions. This light can be used to cast shadows.
Step6:  Animation example
Step7:  Volume rendering and lighting
For volumetric rendering we only support the Phong lighting model. No material needs to be set, only lights need to be setup.
Note that volumetric regions do not cast, not receive shadows.
<ASSISTANT_TASK:>
Python Code:
import ipyvolume as ipv
import numpy as np
def scene():
    f = ipv.figure()
    ipv.xyzlim(-1, 1)
    x = np.array([0.1, 0.5], dtype=np.float32)
    ipv.material_phong()
    s = ipv.scatter(x, x, x, marker="sphere", size=10);
    k = ipv.examples.klein_bottle(show=False)
    ipv.xyzlim(2)
    m = ipv.plot_plane('bottom')
    ipv.show()
    return f
Explanation: Lightning
By default ipyvolume uses a fake lighting model that works ok for depth perception. To get more realistic lighting effects ipyvolume supports a few light models from pythreejs/threejs.
End of explanation
scene()
light = ipv.light_ambient(intensity=0.4);
Explanation: Ambient light
For global illumination, which will not cast shadows
End of explanation
scene()
ipv.light_hemisphere(intensity=1);
Explanation: Hemisphere light
A light source positioned directly above the scene, with color fading from the sky color to the ground color.
This light cannot be used to cast shadows.
End of explanation
f = scene()
ipv.light_ambient(intensity=0.4)
ipv.light_directional(position=[3, 10, 3]);
Explanation: Directional light
A Directional Light source illuminates all objects equally from a given direction. This light can be used to cast shadows. The light is recommended together with hemisphere.
End of explanation
scene()
ipv.light_hemisphere(intensity=0.2)
l = ipv.light_spot(position=[0, 3, 2]);
Explanation: Spot light
A Spot Light produces a directed cone of light. The light becomes more intense closer to the spotlight source and to the center of the light cone. This light can be used to cast shadows.
End of explanation
scene()
ipv.light_hemisphere(intensity=0.2)
l = ipv.light_point(position=[0., 1.6, 1.0]);
Explanation: Point light
A Point Light originates from a single point and spreads outward in all directions. This light can be used to cast shadows.
End of explanation
import ipyvolume as ipv
import ipyvolume.datasets
stream = ipyvolume.datasets.animated_stream.fetch()
print("shape of steam data", stream.data.shape) # first dimension contains x, y, z, vx, vy, vz, then time, then particle
fig = ipv.figure()
# instead of doing x=stream.data[0], y=stream.data[1], ... vz=stream.data[5], use *stream.data
# limit to 50 timesteps to avoid having a huge notebook
ipv.material_physical()
# q = ipv.quiver(*stream.data[:,0:200:10,:2000:10], color="red", size=7)
q = ipv.quiver(*stream.data, color="red", size=7)
ipv.style.use("dark") # looks better
m = ipv.plot_plane('bottom')
m = ipv.plot_plane('back')
m = ipv.plot_plane('left')
ipv
l = ipv.light_directional(position=[20, 50, 20], shadow_camera_orthographic_size=1, far=140, near=0.1);
ipv.animation_control(q, interval=200)
ipv.show()
ipv.light_ambient(intensity=0.4);
Explanation: Animation example
End of explanation
import ipyvolume as ipv
# no material and lighting
ipv.figure()
volume = ipv.examples.example_ylm(shape=64, show=False)
s = ipv.scatter(x=32, y=32, z=50, size=30, marker='sphere', color="green");
volume.tf.level1 = 0.24
volume.tf.opacity1 = 0.1
volume.brightness = 2
ipv.show()
import ipyvolume as ipv
f = ipv.figure(debug=True)
# we only add two lights
ipv.light_hemisphere(intensity=0.8)
ipv.light_directional()
volume = ipv.examples.example_ylm(shape=64, show=False)
ipv.material_phong(specular='white')
s = ipv.scatter(x=32, y=32, z=50, size=30, marker='sphere', color="green");
volume.tf.level1 = 0.24
volume.tf.opacity1 = 0.1
volume.material.specular = 'white'
volume.brightness = 2
ipv.show()
Explanation: Volume rendering and lighting
For volumetric rendering we only support the Phong lighting model. No material needs to be set, only lights need to be setup.
Note that volumetric regions do not cast, not receive shadows.
End of explanation
<END_TASK>