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copied!<p>The following using numpy might get you started. It should be fast enough as it is though you could get much faster even in python (have a look here to see how <a href="http://www.scipy.org/PerformancePython" rel="noreferrer">http://www.scipy.org/PerformancePython</a>).</p> <p>By the way there are several drawbacks in the method described : </p> <ol> <li>you cannot control the speed of the ripples - to do that you would have to modify the equations used in the ripple function (if you figure out how it relates to the wave equation <a href="http://en.wikipedia.org/wiki/Wave_equation" rel="noreferrer">http://en.wikipedia.org/wiki/Wave_equation</a> then you are done)</li> <li>the "depth" of the "pool" is fixed (and probably too shallow). I added a depth parameter to magnify the effect</li> <li>the article reads integer pixel offsets - you would get a much nicer result with interpolated values (i guess you can do that with opengl, but my knowledge in that area is nil)</li> </ol> <p>code:</p> <pre><code>import numpy def ripple(w1, w2, damp, n = 1): for _ in xrange(n): w2 *= -2 w2[1:-1,1:-1] += w1[0:-2, 1: -1] w2[1:-1,1:-1] += w1[2: , 1: -1] w2[1:-1,1:-1] += w1[1:-1, 0: -2] w2[1:-1,1:-1] += w1[1:-1, 2: ] w2 *= .5 * (1. - 1./damp) w1, w2 = w2, w1 def refract(x, y, w, rindex, depth = 10): sx = x[0,1] - x[0,0] sy = y[1,0] - y[0,0] dw_dx = (w[2: ,1:-1] - w[:-2,1:-1]) / sx * .5 dw_dy = (w[1:-1,2: ] - w[1:-1,:-2]) / sy * .5 xang = numpy.arctan(dw_dx) xrefract = numpy.arcsin(sin(xang) / rindex) dx = numpy.tan(xrefract) * dw_dx * depth yang = numpy.arctan(dw_dy) yrefract = numpy.arcsin(sin(yang) / rindex) dy = numpy.tan(yrefract) * dw_dy * depth dx *= numpy.sign(dw_dx) dy *= numpy.sign(dw_dy) xmin = x[0,0] xmax = x[0,-1] x[1:-1,1:-1] += dx x[:,:] = numpy.where(x < xmin, xmin, x) x[:,:] = numpy.where(x > xmax, xmax, x) ymin = y[0,0] ymax = y[-1,0] y[1:-1,1:-1] += dy y[:,:] = numpy.where(y < ymin, ymin, y) y[:,:] = numpy.where(y > ymax, ymax, y) </code></pre> <p>x and y should be grids from a numpy.meshgrid call : here's a sample usage: </p> <pre><code> x,y = meshgrid(x,y) w = 10 * exp(- (x*x + y*y)) w1 = w.copy() x1,y1 = meshgrid(r_[0:len(x):1.0], r_[0:len(y):1.0]) ripple(w, w1, 16) # w1 will be modified refract(x1, y1, w1, rindex=2, depth=10) # x1 and y1 will be modified numpy.around(x1, out=x1) # but you will get better results with interpolate numpy.around(y1, out=y1) # </code></pre>

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