# Title: Coalescence of a pair of Gaussian vortices (Gerris logo)
#
# Description:
#
# This example generates the Gerris desktop logo (Figure \ref{logo}).
#
# A pair of Gaussian vortices slowly merge. This is the primary
# mechanism controlling the evolution of two-dimensional turbulence
# and consequently has been studied in some detail.
#
# \begin{figure}[htbp]
# \caption{\label{logo}Gerris logo and animation.}
# \begin{center}
# \htmladdnormallinkfoot{\includegraphics[width=0.15\hsize]{logo.eps}}{logo.mpg}
# \end{center}
# \end{figure}
#
# Author: St\'ephane Popinet
# Command: gerris2D logo.gfs | gfsview2D logo.gfv
# Required files: logo.gfv
# Version: 100317
# Running time: 5 minutes
# Generated files: logo.mpg logo.png logo.eps
#
1 0 GfsSimulation GfsBox GfsGEdge {} {
    Time { end = 4 }
    Refine 6
    # Initialise a vorticity field given by two gaussian distributions
    InitVorticity {} {
        /* We use nested functions for simplicity (this will not work on MACOSX) */
        double vortex (double xc, double yc, double r) {
            double r2 = (x - xc)*(x - xc) + (y - yc)*(y - yc);
            return 2.*M_PI*exp (- 2.*r2/(r*r));
        }
        double r = 0.01, theta = 30.*M_PI/180.;
        return vortex (-r*sin(theta), r*cos(theta), 0.01) + 
               vortex (r*sin(theta), -r*cos(theta), 0.01);
    }
    AdaptVorticity { istep = 1 } { cmax = 1e-2 maxlevel = 12 minlevel = 6 }
    OutputTime { istep = 1 } stderr
    OutputProjectionStats { istep = 1 } stderr
    OutputSimulation { istep = 10 } stdout
    OutputPPM { istep = 2 } { ppm2mpeg > logo.mpg } {
        v = Vorticity
        min = -0.1348 max = 6.22219
        # Only generate the movie in a small box centered on the
	# origin. We also need to make sure that box size is a multiple
	# of 1./64. so that the PPM image size stays constant (ffmpeg
	# crashes on variable image sizes).
        condition = (Level < 6 || 
                     (x >= -3./128. && x <= 3./128. && y >= -3./128. && y <= 3./128.))
    }
    EventScript { start = end } {
        echo "Save logo.ppm { width = 1024 height = 1024 }"
        sleep 5 # to wait for GfsView to finish writing the image
        convert -transparent "#0000FF" logo.ppm -geometry 156x156 logo.png
        montage -background white -geometry +0+0 logo.png logo.eps
        rm -f logo.ppm
    }
}
GfsBox {}