from numpy import*
from Tkinter import *
import time

dt = 0.0001
dx = 0.1
v = 100 #Courant condition says dx/dt >= v
gamma = 0
c1 = (v**2) * (dt**2) / (dx**2)
c2 = gamma*dt / dx**2

nodes = 30
source_node = nodes/3 #point of application of initial pulse
x = arange(0, nodes, 1)
u_new = zeros(nodes)
u = zeros(nodes)
u_old = zeros(nodes)

##--Tkinter stuff--
t_start = time.time()#for referencing
height = 300.0
width = 400.0
center = height//2
x_factor = width/(nodes-1)
y_factor = 200
##------------------
u[source_node] = -10
u_old[source_node] = -10
	
def paint(canvas, parent):
	for i in range (1, nodes-1):
		U1 = u[i+1] - 2*u[i] + u[i-1]
		U0 = u_old[i+1] - 2*u_old[i] + u_old[i-1]
		u_new[i] = c1*U1 + c2*(U1-U0) + 2.0*u[i] - u_old[i]
	for i in range (0, nodes):
		u_old[i] = u[i]
		u[i] = u_new[i]
	xy=[]
	for i in range(0, nodes):
		xy.append((int)(i*x_factor))
		xy.append((int)(u_new[i]*y_factor)+center)
	#time.sleep(0.001)	
	c.coords("curve", *xy)
	parent.after_idle(paint,parent,canvas)
	##------------------	
#--Tkinter stuff:--
root = Tk()
root.title("Animated wave equation - initial pulse at L/3")
root.bind('q','exit')
c = Canvas(width=width, height=height, bg='white')
c.pack()
c.create_line(tag = "curve", *zeros(2*width), fill='blue')	
root.after(100,paint,root,c)
root.mainloop()	
##------------------