### Animate 3D Structure Field with Mayavi

Source: https://wiechapeter.gitlab.io/pyGDM2-doc

This script demonstrates how to create a 3D animation of the electric field around a nanostructure using pyGDM2 and Mayavi. It requires pyGDM2, mayavi, and ffmpeg.

```python
from pyGDM2 import visu3d
from mayavi import mlab

fig = mlab.figure( size=(600, 300), bgcolor=(1.0, 1.0, 1.0), fgcolor=(0.,0.,0.) )

## structure
visu3d.structure(sim, axis_labels=False, draw_substrate=False,
                opacity=0.1, show=False)


## 3D field-animation
ani2 = visu3d.animate_vectorfield(NF, Nframes=100, scale=8,
                        draw_struct=False,
                        draw_substrate=False, substrate_size=1.1,
                        colormap='Blues', clim=[0.0, 0.5],
                        fig=fig, view=(85, -45, 350, (0,0,-15)),
                        ffmpeg_args="-b:v 1.5M -c:v libx264", mov_file="3D.mp4",
                        save_anim=True,
                        opacity=0.5)

```

--------------------------------

### Generate and Animate Structure Field

Source: https://wiechapeter.gitlab.io/pyGDM2-doc

This script generates a nanostructure from an image, calculates the time-harmonic electric field, and creates an animation of the field. It requires pyGDM2, matplotlib, and ffmpeg.

```python
## --- load pyGDM
from pyGDM2 import structures
from pyGDM2 import materials
from pyGDM2 import fields

from pyGDM2 import core
from pyGDM2 import propagators
from pyGDM2 import tools
from pyGDM2 import visu

import matplotlib.pyplot as plt


#===============================================================
# Setup the simulation
#===============================================================
## --- structure
step = 8.0
geometry = structures.image_to_struct("pyGDM_logo_static.png",
                      useDarkPixel=1, threshold=100, H=1,
                      nm_per_pixel=1.*step, stepsize=step)
material = materials.gold()
struct = structures.struct(step, geometry, material)

## --- incident field
field_generator = fields.plane_wave
kwargs = dict(theta=45.0)
wavelengths = [700]
efield = fields.efield(field_generator, wavelengths=wavelengths,
                                                   kwargs=kwargs)

## --- vacuum environment
dyads = propagators.DyadsQuasistatic123(n1=1)

## --- simulation object
sim = core.simulation(struct, efield, dyads)


#===============================================================
# Run the simulation
#===============================================================
E = core.scatter(sim)
NF = tools.get_field_as_list_by_fieldindex(sim, 0)


#===============================================================
# create the field-animation
#===============================================================
## setup figure / axes
plt.figure(figsize=(6.0,2.5))
ax = plt.subplot(aspect='equal')
plt.axis('off')
plt.subplots_adjust(left=0, right=1, bottom=0,top=1)

## geometry
s = visu.structure(sim, scale=0.1, color='.75', show=0)

## field-animation
config_vectorfield = dict(cmin=0.5, cmap=plt.cm.Blues,
                        borders=5, vecwidth=0.8)
ani = visu.animate_vectorfield(NF, Nframes=100, scale=12,
                            kwargs=config_vectorfield,
                            ax=ax, show=False)
## save video to file
ani.save('pyGDM_logo.mp4', writer="ffmpeg",
         codec='h264', bitrate=1500)

```

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