from random import *
from visual import *

print """
Electromagnetism: Gauss Electric Law(v2.75) 2008-01-20
Rob Salgado (salgado@physics.syr.edu)

Electric Field vectors are blue.
"""

scene=display(
    width=800,height=600,
    x=0, y=0)

scene.ambient=0.24
colorBackground=[color.black,color.white]
colorScheme=0

scene.background=colorBackground[colorScheme]
scene.title="GAUSS: Radial E's are associated with ElectricPoint-Charges"
scene.range=(2.5,2.5,2.5)

scene.forward=(-0.162765,0.013403,-0.986574)

#based on
#
#   http://www.math.niu.edu/~rusin/known-math/97/spherefaq
#then
#   http://astronomy.swin.edu.au/~pbourke/geometry/spherepoints/source1.c
#



p=[]
sp=[]

theta=[]
phi=[]

N=24

for k in arange(0, N):
   #print "k=",k,
   h = -1 + 2*k/(N-1.)
   #print "h=",h,
   theta.append( arccos(h) )
   if k==0 or k==N-1:
       phi.append( 0 )
       #print "q=0.00"
   else:
       phi_last=phi[-1]
       q=N*(1-h*h)
       #print "q=",q
       phi.append( phi_last + 3.6/sqrt(q))


for i in arange(0,N):
    p.append(vector( cos(phi[i])*sin(theta[i]),sin(phi[i])*sin(theta[i]), cos(theta[i]) ))
#    sp.append( sphere(pos=p[-1],radius=0.05) )
    
counter=0
countmax=100

n=len(p)
print n

while(counter<countmax):
    minp1=0
    minp2=1
    mind=mag2(p[minp1]-p[minp2])
    maxd=mind

    for i in arange(0,n-1):
        for j in arange(i+1, n):
            d=mag2(p[i]-p[j])
            if (d < mind):
                   mind = d;
                   minp1 = i
                   minp2 = j
            if (d > maxd):
                   maxd = d
    p1=p[minp1]
    p2=p[minp2]

    p[minp2] = norm( p1 + 1.1 * (p2 - p1) )
    p[minp1] = norm( p1 - 0.1 * (p2 - p1) )

    counter+=1
   
####################################################

sphere(radius=0.04,color=color.cyan)

E=0.5*1/mag2(p[0])
for i in arange(0,N):
    A=arrow(pos=p[i],axis=E*p[i],shaftwidth=0.04,fixedwidth=1,color=color.blue)
    box(pos=p[i]+A.axis/4.,axis=A.axis,length=mag(A.axis)/2.,height=0.04,width=0.04,color=color.blue)

E /=4.
for i in arange(0,N):
    A=arrow(pos=2*p[i],axis=E*p[i] ,shaftwidth=0.04,fixedwidth=1,color=color.blue)
    box(pos=2*p[i]+A.axis/4.,axis=A.axis,length=mag(A.axis)/2.,height=0.04,width=0.04,color=color.blue)
    

    
#Now... WHEN AN OBJECT IS PICKED,
#TRANSLATE THE scene.center TO THE OBJECT'S POSITION        
while 1:
    rate(5)
    if scene.mouse.clicked:
        scene.mouse.getclick()
        newPick=scene.mouse.pick
        if newPick !=None:
            ### ANIMATE TO SELECTED POSITION
            tempcolor=newPick.color
            newPick.color=color.yellow
            target=newPick.pos
            step=(target-scene.center)/20.
            for i in arange(1,20,1):
                rate(10)
                scene.center +=step
                scene.scale *= 1.037  #(1.037**19=1.99)
            newPick.color=tempcolor

    if scene.kb.keys: # is there an event waiting to be processed?
        s = scene.kb.getkey() # obtain keyboard information
        if s=='z':
            print "scene.center=(%f,%f,%f)"  % tuple(scene.center)
            print "scene.forward=(%f,%f,%f)"  % tuple(scene.forward)
            print "scene.range=(%f,%f,%f)"  % tuple(scene.range)

        if s=='n':
            colorScheme = (colorScheme+1)%2 #TOGGLE colorScheme
            scene.background=colorBackground[colorScheme]