English: A movie showing the similarity between Heaviside and steep sigmoidal models. In panel A the values of u from three direct numerical simulations are overlaid by assigning each one a part of the red-green-blue color space. The Heaviside model, cf. Figure 1 and the video in Additional file 1, determines red intensity, whereas calculations with a sigmoidal firing rate 1/{1+exp[−(u−h)/σ]}, cf. Figure 3, determine intensities in green for σ=0.01 and blue for σ=0.02. Where all three models predict the same value for u, a gray color results as shown by the colorbar. Where the models predict different values, colored patches show up. In panel B the same data is displayed, but this time only the u=h interface is plotted with the same color assignment. From about time α⋅t=550 onward the structure starts to interfere with itself across the grid edges. (AVI 18.0 MB)