from __future__ import division
from visual import *
print """
Ruth Chabay Spring 2001
Click to start waves moving.
"""

scene.x = scene.y = 0
scene.width = 1000
scene.height = 1000
scene.forward = (0,-1,-2)
scene.background = color.white

ihat=vector(1,0,0)
lamb = 1e-1     ##1e-10
c = 3e8
omega = 2*pi*c/lamb
d = 2*lamb      ## slit spacing

Evec1 = []
Evec2 = []

dist_to_screen = 4.0*lamb    ## dist to screen
scene.center = (dist_to_screen*.65,-d/2.,0)
ds = lamb/20.
dt = lamb/c/100.
E0 = lamb/3.0

screen = curve(pos = [(dist_to_screen,0,0),(dist_to_screen,0,2*d)],
               color=(0.6,0.6,0.6))
slit1 = vector(0, 0, -d/2.) ## coord of slit 1
slit2 = vector(0, 0, d/2.)  ## coord of slit 2

## found by search: see interf02_loc.py
max1 = vector(dist_to_screen,0,0)
max2 = vector(dist_to_screen,0,0.24)
min1 = vector(dist_to_screen,0,0.105) ## or z=0.11

## vectors from slits to max2:
r1 = max2 - slit1
r2 = max2 - slit2

# vectors from slits to loc. on screen
##r1arr=arrow(pos=slit1,axis=r1, color=color.red, shaftwidth=lamb/80.)
dr1 = ds*norm(r1)
##r2arr=arrow(pos=slit2, axis=r2, color=color.green, shaftwidth=lamb/80.)
dr2 = ds*norm(r2)

rr1 = slit1 + vector(0,0,0) ## current loc along wave 1
rr2 = slit2 + vector(0,0,0) ## current loc along wave 2

i1 = None
i2 = None

## create first wave
ct = 0
while ct < 120:
    ea = arrow(pos=rr1, axis=(0,E0*cos(2*pi*mag(rr1-slit1)/lamb),0), color=color.red,
               shaftwidth=lamb/40.)
    ba = arrow(pos=rr1, axis=(0,0,0), color=(.4,.4,1),
               shaftwidth=lamb/40., visible=0)
    ea.B = ba
    if abs(ea.x - dist_to_screen) < 0.002 and i1==None:
        i1 = ea
        i1.visible = 0
    else:
        Evec1.append(ea)
    rr1 = rr1 + dr1
    ct = ct + 1
    
## create second wave
ct = 0
while ct < 100:
    ea = arrow(pos=rr2, axis=(0,E0*cos(2*pi*mag(rr2-slit2)/lamb),0), color=(1.,.6,0),
               shaftwidth=lamb/40.)
    ba = arrow(pos=rr2, axis=(0,0,0), color=color.cyan,
               shaftwidth=lamb/40., visible=0)
    ea.B = ba
    if abs(ea.x - dist_to_screen) < 0.002 and i2==None:
        i2 = ea
##        i2.visible = 0
    else:
        Evec2.append(ea)
    rr2 = rr2 + dr2
    ct = ct + 1

i2.color = color.green
i2.B.color = color.magenta
scene.autoscale = 0
scene.mouse.getclick()

t=0.0
while 1:
    rate(50)
    if scene.mouse.clicked:     ## toggle vis of mag field vectors
        scene.mouse.getclick()
        for a in Evec1 + Evec2 :
            a.B.visible = not(a.B.visible)
        i2.B.visible = not(i2.B.visible)
    t = t+dt
    for ea in Evec1:
       ea.axis = (0,E0*cos(omega*t - 2*pi*mag(ea.pos-slit1)/lamb),0)
       ea.B.axis = -cross(ea.axis,ihat)*.7       
    for ea in Evec2:
       ea.axis = (0,E0*cos(omega*t - 2*pi*mag(ea.pos-slit2)/lamb),0)
       ea.B.axis = -cross(ea.axis,ihat)*.7
# superposition
    sum = E0*cos(omega*t - 2*pi*mag(i1.pos-slit1)/lamb)+E0*cos(omega*t - 2*pi*mag(i2.pos-slit2)/lamb)
    i2.axis = vector(0,sum,0)    
##    i2.axis = i1.axis + i2.axis
    i2.B.axis = -cross(i2.axis,ihat)*.7