README.md

--------------UPDATED VERSION

shadowplay.py

import shapely
from shapely import speedups, wkb
from shapely.geometry import *
from osgeo import ogr
import time, random
from math import *

if shapely.speedups.available:
    shapely.speedups.enable()

source = ogr.Open('data/diss.shp')
l = source.GetLayer(0)
f = l.GetNextFeature()
countries = shapely.wkb.loads(f.GetGeometryRef().ExportToWkb())

shpdriver = ogr.GetDriverByName('ESRI Shapefile')
squiggle_ds = shpdriver.CreateDataSource("out/shadow%d.shp" % time.time())
lyr = squiggle_ds.CreateLayer('squiggle')

xs = [x * 0.5 for x in range(-360, 360)]

for y in range(-80, 80):
    lsp = []
    for x in xs:
        p = Point((x, y))
        if p.intersects(countries):
            lsp.append((x, y + random.random() - 0.5))
        else:
            lsp.append((x, y + (sin(x * (0.05 + (abs(y) / 80.0) )))))
    ls = LineString(lsp)
    q_geom = ogr.CreateGeometryFromWkb(ls.wkb)
    feat = ogr.Feature(lyr.GetLayerDefn())
    feat.SetGeometry(q_geom)
    lyr.CreateFeature(feat)
    print "created feature for %d" % y

Publish the data!! ;)
(the source data)

@teeler https://gist.github.com/tmcw/5196243