#! /usr/bin/python
from __future__ import print_function, division

from visual import *
import os               # needed for catching ^C
import traceback        # needed for catching ^C
import sys
import Image

def make_svg():
  ouch = open('/tmp/mag.svg', 'w')
# some svg graphics:
  model = '''  <path
     inkscape:connector-curvature="0"
     id="SEQUENCE"
     d="m XSIZE2,WHERE 0,2 XSIZE2,0 0,-BLINEW z"
     style="fill:#00ff00;fill-opacity:1;fill-rule:evenodd;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" />'''

  denom = 10    # number of parallels of B per hemisphere, including equator
  seq = 0
  page = 512    # size of image, in pixels
  Blinewidth = 2 # width of B-field line, in pixels
####  for ii in range(-(denom-1), denom):
  for ii in range(0, denom):
    where = page/2 - asin(ii/denom)*page/pi
    where -= Blinewidth/2        # line is /centered/ on desired position
    svg = model
    svg = svg.replace("WHERE", "%8.4f" %where)
    svg = svg.replace("XSIZE2", "%8.4f" %(page/2))
    svg = svg.replace("BLINEW", "%8.4f" %Blinewidth)
    svg = svg.replace("SEQUENCE", "mag%d" % seq)
    seq += 1
    print (svg, file=ouch)

# next:
# :; inkscape --export-png=spherical-field.png  \
#       --export-area-page spherical-field.svg
#
# :; xwd -nobdrs -out /tmp/foo.xwd
# :; convert /tmp/foo.xwd img48/transverse-spherical-field.png

def make_wavefront():
  # open the graphics window:
  scene = display(title='whatever',
         x=0, y=0, width=400, height=400,
         range=1.3, background=(1,1,1))

  sun1 = distant_light(direction=(1, 0, 0), color=color.white)
  sun2 = distant_light(direction=(0, 1, 0), color=color.white)
  sun3 = distant_light(direction=(0, 0, 1), color=color.white)
  scene.lights = [sun1, sun2, sun3]

  im = Image.open('spherical-field.png')
                  # size must be power of 2, ie 128 x 128
  tx = materials.texture(data=im, mapping='spherical')

  center = sphere(pos=(0, 0, 0), radius=.03, color=color.black)
  main = sphere(pos=(0, 0, 0), radius=1, material=tx)
  main.rotate(angle=-.80, axis=(0,1,0))
  main.rotate(angle=.7, axis=(1,0,0))

# some sort of while loop is required, if you want to catch ^C:
  counter = 0;
  while 1:
    rate(30)

def doit():
  try:
    ## make_svg()               # useful during development
    make_wavefront()

  except KeyboardInterrupt as e:
    print ('...Interrupt...')
    os._exit(1)

  except:
    #xxx print("Unexpected error:\n", sys.exc_info())
    print("Unexpected error... ", end='')
    sys.stdout.flush()

# do whatever other cleanup is needed ....

# Use print_exc() instead of raise, because we want to retain control,
# so we can force an exit that actually exits,
# rather than hanging around with a graphics window open.
  traceback.print_exc()
  os._exit(1)

# idiomatic way of figuring out if this is being used as a
# main program, as opposed to a library:

if __name__ == '__main__':
  doit()