#!/usr/bin/env python

# Author: Raashid Baig <raashid@aero.iitb.ac.in>
# License: BSD Style.

from enthought.tvtk.tools.visual import *
from numpy import zeros, float, arange
from math import sin, pi

def main():
  dt = 0.1

  x = arange(-50,50)
  wpoints1 = zeros((100,3), float)
  wpoints2 = zeros((100,3), float)
  wpoints3 = zeros((100,3), float)
  wpoints4 = zeros((100,3), float)
  
  for i in range (0,100,1):
    wpoints1[i] = [x[i], -30, 0]
    wpoints2[i] = [x[i], -15, 0]
    wpoints3[i] = [x[i], 0, 0]
    wpoints4[i] = [x[i], 15, 0]
    
  band1 = Curve( points = wpoints1, k = 6.0, color = (1,0,0),  mass = 2.0, radius = 0.5, momentum = zeros((100, 3), float))

  band2 = Curve( points = wpoints2, k = 6.0, color = (1,1,0),  mass = 2.0, radius = 0.5, momentum = zeros((100, 3), float))

  band3 = Curve( points = wpoints3, k = 6.0, color = (0,1,0),  mass = 2.0, radius = 0.5, momentum = zeros((100, 3), float))

  band4 = Curve( points = wpoints4, k = 6.0, color = (0,0,1),  mass = 2.0, radius = 0.5, momentum = zeros((100, 3), float))

  for i in range(0,25,1):
    band1.momentum[i,1] = sin(x[i]*pi/25.0)*3   # half-wave pulse

  for i in range(0,25,1):
    band2.momentum[i,1] = sin(x[i]*2*pi/25.0)*5   # full-wave pulse
    
  for i in range(0,25,1):
    band3.momentum[i,0] = sin(x[i]*pi/25.0)*5   # compresion pulse

  for i in range(0,100,1):
    band4.momentum[i,1] = sin(x[i]*4*pi/100.0)*2   # standing wave  
    
  def anim():
    band1.momentum[0] = band1.momentum[-1] = MVector(0,0,0)
    band2.momentum[0] = band2.momentum[-1] = MVector(0,0,0)
    band3.momentum[0] = band3.momentum[-1] = MVector(0,0,0)
    band4.momentum[0] = band4.momentum[-1] = MVector(0,0,0)
      
    band1.points = band1.points + (band1.momentum/band1.mass*dt)
    band2.points = band2.points + (band2.momentum/band2.mass*dt)
    band3.points = band3.points + (band3.momentum/band3.mass*dt)
    band4.points = band4.points + (band4.momentum/band4.mass*dt)

    force1 = band1.k * (band1.points[1:] - band1.points[:-1])
    force2 = band2.k * (band2.points[1:] - band2.points[:-1])
    force3 = band3.k * (band3.points[1:] - band3.points[:-1])
    force4 = band4.k * (band4.points[1:] - band4.points[:-1])

    band1.momentum[:-1] = band1.momentum[:-1] + force1 * dt
    band2.momentum[:-1] = band2.momentum[:-1] + force2 * dt
    band3.momentum[:-1] = band3.momentum[:-1] + force3 * dt
    band4.momentum[:-1] = band4.momentum[:-1] + force4 * dt

    band1.momentum[1:] = band1.momentum[1:] - force1 * dt
    band2.momentum[1:] = band2.momentum[1:] - force2 * dt
    band3.momentum[1:] = band3.momentum[1:] - force3 * dt
    band4.momentum[1:] = band4.momentum[1:] - force4 * dt

  a = iterate(20, anim)
  show()
  return a

if __name__ == '__main__':
  main()