plotting.py

# Generalized Lagrangian Networks | 2020
# Miles Cranmer, Sam Greydanus, Stephan Hoyer (...)

import numpy as np # get rid of this eventually
from functools import partial # reduces arguments to function by making some subset implicit

# visualization
import matplotlib.pyplot as plt
from matplotlib.patches import Circle
from moviepy.editor import ImageSequenceClip
from functools import partial
import proglog
from PIL import Image

from .utils import radial2cartesian


def plot_dblpend(ax, i, cart_coords, l1, l2, max_trail=30, trail_segments=20, r = 0.05):
    # Plot and save an image of the double pendulum configuration for time step i.
    plt.cla()

    x1, y1, x2, y2 = cart_coords
    ax.plot([0, x1[i], x2[i]], [0, y1[i], y2[i]], lw=2, c='k') # rods
    c0 = Circle((0, 0), r/2, fc='k', zorder=10) # anchor point
    c1 = Circle((x1[i], y1[i]), r, fc='b', ec='b', zorder=10) # mass 1
    c2 = Circle((x2[i], y2[i]), r, fc='r', ec='r', zorder=10) # mass 2
    ax.add_patch(c0)
    ax.add_patch(c1)
    ax.add_patch(c2)

    # plot the pendulum trail (ns = number of segments)
    s = max_trail // trail_segments
    for j in range(trail_segments):
        imin = i - (trail_segments-j)*s
        if imin < 0: continue
        imax = imin + s + 1
        alpha = (j/trail_segments)**2 # fade the trail into alpha
        ax.plot(x2[imin:imax], y2[imin:imax], c='r', solid_capstyle='butt',
                lw=2, alpha=alpha)

    # Center the image on the fixed anchor point. Make axes equal.
    ax.set_xlim(-l1-l2-r, l1+l2+r)
    ax.set_ylim(-l1-l2-r, l1+l2+r)
    ax.set_aspect('equal', adjustable='box')
    plt.axis('off')


def fig2image(fig):
  fig.canvas.draw()
  data = np.fromstring(fig.canvas.tostring_rgb(), dtype=np.uint8, sep='')
  image = data.reshape(fig.canvas.get_width_height()[::-1] + (3,))
  return image


def get_dblpend_images(y, fig, ax, l1=1, l2=1, verbose=True):
  theta1, theta2 = y[:, 0], y[:, 1]
  cart_coords = radial2cartesian(theta1, theta2, l1, l2)

  images = [] ; di = 1
  N = len(y)
  for i in range(0, N, di):
    if verbose:
      print("{}/{}".format(i // di, N // di), end='\n' if i//di%15==0 else ' ')
    plot_dblpend(ax, i, cart_coords, l1, l2)
    images.append( fig2image(fig) )
  return images