Making movies of your BFE field quantities

Read in config from EXP yaml file and render a movie from the coefficient file. This notebook will create the movie for either the disk or the halo by changing the component variable from ‘dark’ to ‘star’ and vice versa.

Begin with the usual imports

You may need to append the pyEXP location to your Python path, depending on your installation.

import os
import copy
import yaml
# sys.path.append('/my/path/to/site-packages')
import pyEXP
import numpy as np
import matplotlib.pyplot as plt
from matplotlib import ticker, cm, colors
from os.path import exists

plt.rcParams['figure.figsize'] = [12, 9]

Configure the basis and component

At minimum, you need to:
- Define the EXP config file to import the
config.
- Define the target component.

The rest of the notebook should then run without changes.

Two optional parameters: - The half size of each axis - Number of pixels along each axis

# key parameters
exp_config = 'step3_try9.yml'
component  = 'star'  # You can make the halo (disk) movie by changing this to 'dark' ('star')

# options
size       = 0.04
npix       = 50

Switch to the working directory

I like to be explicit about my working directory but you don’t need to do this here. It would be sufficient to simply pass the full path to the coefficient factory below or launch the notebook from a working directory.

# os.chdir('/data/Nbody/Test')

Read the EXP config file, generate the basis from the config, and get the run tag for convenience

# Open and read the yaml file
#
with open(exp_config, 'r') as f:
    yaml_db = yaml.load(f, Loader=yaml.FullLoader)

# Grab both star and dark, although I'm mostly interested in star at this point
#
for v in yaml_db['Components']:
    if v['name'] == component:
        config = yaml.dump(v['force'])

# Construct the basis instance
#
basis = pyEXP.basis.Basis.factory(config)

# Get the runtag
#
runtag = yaml_db['Global']['runtag']
print("\nRuntag from {} is: {}".format(exp_config, runtag))
coeffile = 'outcoef.{}.{}.h5'.format(component, runtag)
print("\nCoef file is:", coeffile)

Read the coefficients

coefs = pyEXP.coefs.Coefs.factory(coeffile)

Set the output field grid and render the slices

times = coefs.Times()
pmin  = [-size, -size, 0.0]
pmax  = [ size,  size, 0.0]
grid  = [ npix,  npix,   0]

fields = pyEXP.field.FieldGenerator(times, pmin, pmax, grid)

print('Created fields instance')

surfaces = fields.slices(basis, coefs)

Make a movie frames

# Get the shape
keys = list(surfaces.keys())
nx = surfaces[keys[0]]['d'].shape[0]
ny = surfaces[keys[0]]['d'].shape[1]

# Make the mesh
x = np.linspace(pmin[0], pmax[0], nx)
y = np.linspace(pmin[1], pmax[1], ny)
xv, yv = np.meshgrid(x, y)

plt.rcParams.update({'font.size': 22})

# Fix the contour levels to prevent jitter in the movie
cbar1 = 10**np.arange(0.0, 4.01, 0.1)
cbar2 = 10**np.arange(0.0, 4.01, 0.4)

# Frame counter
icnt = 0
cmap = copy.copy(plt.colormaps['viridis'])

N = cmap.N
cmap.set_under(cmap(1))
cmap.set_over(cmap(N-1))

# Iterate through the keys
for v in keys:
    fig, ax = plt.subplots(1, 1, figsize=(24, 20))

    mat = surfaces[v]['d']
    for i in range(mat.shape[0]):
        for j in range(mat.shape[1]):
            if mat[i, j] < 1.0: mat[i, j] = 1.0
            if mat[i, j] > 10000.0: mat[i, j] = 10000.0

    cont1 = ax.contour(xv, yv, mat.transpose(), cbar2, colors='k')
    # You can label the contours inline by uncommenting the next two lines...
    # ax[0].clabel(cont1, fontsize=9, inline=True)
    # cont2 = ax.contourf(xv, yv, surfaces[v]['d'].transpose(), cbar2, vmin=cbar2[0], vmax=cbar2[-1])
    cont2 = ax.contourf(xv, yv, mat.transpose(), cbar1, locator=ticker.LogLocator())
    plt.colorbar(cont2, ax=ax)
    ax.set_xlabel('x')
    ax.set_ylabel('y')
    ax.set_title('T={:4.3f}'.format(v))

    fig.savefig('{}_movie_{}_{:04d}.png'.format(component, runtag, icnt), dpi=75)
    plt.close()

    icnt += 1

Make a mp4 file from the frames using ffmpeg

This will only work if you have ‘ffmpeg’ installed, of course …

os.system('ffmpeg -y -i \'{0}_movie_{1}_%04d.png\' movie_{0}_{1}.mp4'.format(component, runtag))

Preview the new movie

from IPython.display import Video
Video('movie_{0}_{1}.mp4'.format(component, runtag), embed=True, width=800)