I made a little forest fire animation. My codes are at the end of the question.
The code forestfire.py contains the functions that will spread the fire to all the forest. Then forestfire_test.py import forestfire.py as ff and from there I can set the forest on fire with my mouse by clicking on the array displayed by matplotlib.
Here is some information before I ask my question :
- No tree :
forest[i,j] = 0 - A tree :
forest[i,j] = 1 - A tree on fire :
forest[i,j] = 2 - Hashes :
forest[i,j] = 3
Basically what happens is that forest is 2 dimensional array of size n by m made of numbers between 1 and 0. The function onclick sets on fire the forest and while the forest still has trees on fire the function spreadfire spread the fire.
With the function onclick I can set the forest on fire (if I click on the array the trees will become red) and with the function start I can execute the code thanks to the button Start.
Now the issue is that the first time I execute the code it does not know what ani is (NameError: global name 'ani' is not defined) – which is normal because I call the animation ani (by trying to save it) before I even call the function start. But if I try to save ani in the function start I get a blank plot – which is also normal.
To sum up I need to save the animation after the function start is called but I can’t save it at the end of the function start otherwise I will get a blank plot. Can someone tell me what should I do?
PS : I use Spyder and the IPython console And please tell me if my explanations are not clear enough.
forestfire_test.py
import forestfire as ff
import numpy as np
import matplotlib.pylab as plt
import matplotlib.colors as mcolors
from matplotlib import cm
from matplotlib.widgets import Button, Cursor
global forest
forest = np.random.rand(100,100)
# Colormap
greens = cm.Greens(np.linspace(0,1, num=50))
greensfill = cm.Greens(np.ones(25))
red = [(1,0,0,1)]*len(greens)
gray = [(.5,.5,.5,1)]*len(greens)
colors = np.vstack((greens, greensfill, red, gray))
mycmap = mcolors.LinearSegmentedColormap.from_list('my_colormap', colors)
# Figure
fig, ax = plt.subplots(figsize=(10,5))
fig.subplots_adjust(right=1.3)
im = ax.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower', vmin=0, vmax=3.5)
ax.set_xlabel("X")
ax.set_ylabel("Y")
ax.tick_params(direction='out')
cursor = Cursor(ax, useblit=True, color='red', linewidth=1)
plt.show()
# Coordinates
def onclick(event):
x, y = int(event.xdata), int(event.ydata)
forest[y,x] = 2.
im.set_data(forest)
fig.canvas.draw_idle()
fig.canvas.mpl_connect('button_press_event', onclick)
# Start button
def start(event):
global ani
ani = ff.forestfire(forest)
button_ax = plt.axes([0.15, 0.45, 0.2, 0.1])
button = Button(button_ax, 'Start', color='lightgrey', hovercolor='grey')
button.on_clicked(start)
# Animation
ani.save("forestfire_test.mp4", writer = 'ffmpeg', fps=5, dpi=500)
forestfire.py
from random import random
import numpy as np
from numpy.random import choice
import matplotlib.pylab as plt
import matplotlib.colors as mcolors
from matplotlib import cm
import matplotlib.animation as animation
def hazard(p):
r=random()
assert p>=0 and p<=1
return r <= p
def chg(case):
if case > 1.:
return 1.
else:
return case
def spreadfire(forest):
n,m=forest.shape
c = np.copy(forest)
L = xrange(3)
for i in xrange(n):
for j in xrange(m):
if c[i,j] == 2.:
sautX, sautY = choice([0,1,40],p=[0.4999,0.4999,0.0002]), choice([0,1,40],p=[0.4999,0.4999,0.0002])
Y, X = xrange(max(0,i-1-sautY),min(n,i+2+sautY),sautY+1), xrange(max(0,j-1-sautX),min(m,j+2+sautX),sautX+1)
for y1,y2 in zip(Y,L):
for x1,x2 in zip(X,L):
if hazard(chg(c[y1,x1])):
forest[y1,x1] = 2.
return forest
def forestfire(forest):
fig, ax = plt.subplots()
movie, hashes = [], []
# Colormap
greens = cm.Greens(np.linspace(0,1, num=50))
greensfill = cm.Greens(np.ones(25))
red = [(1,0,0,1)]*len(greens)
gray = [(.5,.5,.5,1)]*len(greens)
colors = np.vstack((greens, greensfill, red, gray))
mycmap = mcolors.LinearSegmentedColormap.from_list('my_colormap', colors)
# Initialization
k = 0
firefront = 5
forest = spreadfire(forest)
c = np.copy(forest)
c[np.where(c==2.)] = 3.
hashes.append(c)
im = plt.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower', vmin=0, vmax=3.5)
movie.append([im])
# Fire propagation
while np.count_nonzero(forest == 2.) != 0:
k += 1
print k
if k < firefront:
forest = spreadfire(forest)
c = np.copy(forest)
c[np.where(c==2.)] = 3.
hashes.append(c)
im = plt.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower', vmin=0, vmax=3.5)
movie.append([im])
else:
forest = spreadfire(forest)
c = np.copy(forest)
c[np.where(c==2.)] = 3.
hashes.append(c)
forest[np.where(hashes[0]==3.)] = 3.
im = plt.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower', vmin=0, vmax=3.5)
movie.append([im])
hashes.remove(hashes[0])
return animation.ArtistAnimation(fig, movie, blit=True, repeat_delay=100)
