Prefuse graph manually set force parameters

Question

Like here, my Prefuse graph is too dense to see anything. So I tried the approach suggested by @bcr in the accepted answer. However, it does not work for me. This is what I tried:

I retrieved the default settings. Then I changed the 2nd parameter of NBodyForce from ForceSimulator (called Distance) and the second parameter of SpringForce (called DefaultSpringLength) and fed them—along with the other default values—into my new ForceSimulator. But nothing in the output changed. What am I getting wrong?

This is my code:

private static void visualiseGraph(Graph graph) {
    Visualization vis = new Visualization();
    vis.add("graph", graph);
    LabelRenderer r = new LabelRenderer("someLabel");
    r.setRoundedCorner(8, 8);
    vis.setRendererFactory(new DefaultRendererFactory(r));
    ColorAction fill = new ColorAction("graph.nodes",
            VisualItem.FILLCOLOR, ColorLib.rgb(190,190,255));
    ColorAction text = new ColorAction("graph.nodes",
        VisualItem.TEXTCOLOR, ColorLib.gray(0));
    ColorAction edges = new ColorAction("graph.edges",
        VisualItem.STROKECOLOR, ColorLib.rgb(255,180,180)); 
    ActionList color = new ActionList();
    color.add(fill);
    color.add(text);
    color.add(edges);
    ActionList layout = new ActionList(Activity.INFINITY);
    Force[] originalForces = new ForceDirectedLayout("").getForceSimulator().getForces();
    ForceDirectedLayout fdl = new ForceDirectedLayout("graph"){
        @Override
        public ForceSimulator getForceSimulator() {
            ForceSimulator fs = new ForceSimulator();
            fs.addForce(new NBodyForce(originalForces[0].getParameter(0), 100, originalForces[0].getParameter(2)));
            fs.addForce(originalForces[1]);
            fs.addForce(new SpringForce(originalForces[2].getParameter(0), 100));
            return fs;
        }
    };
    layout.add(fdl);
    layout.add(new RepaintAction());
    vis.putAction("color", color);
    vis.putAction("layout", layout);
    Display display = new Display(vis) {
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(W, H);
        }
    };
    display.pan(W / 2, H / 2);
    display.addControlListener(new DragControl()); // drag items around
    display.addControlListener(new PanControl());  // pan with background left-drag
    display.addControlListener(new ZoomControl()); // zoom with vertical right-drag
    JFrame frame = new JFrame("prefuse example");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(display);
    frame.pack();           
    frame.setVisible(true); 
    vis.run("color");
    vis.run("layout");
}

Answer 1

One approach might be to add a JForcePanel, which is a

Swing component for configuring the parameters of the Force functions in a given ForceSimulator. Useful for exploring different parameterizations when crafting a visualization.

This might help you to find the optimal parameters to use in your implementation of getForceSimulator().

ForceSimulator fsim = ((ForceDirectedLayout) layout.get(0)).getForceSimulator();
JForcePanel fpanel = new JForcePanel(fsim);
frame.add(fpanel, BorderLayout.SOUTH);

Among the demos included in the distribution, prefuse.demos.GraphView is a complete example. Empirically, it seems as though some parameters have more or less effect depending on the chosen data set.

Addendum: Looking closer, I see that your approach leaves the internal state of fdl unchanged. Instead, create a new ForceSimulator and use it in the layout and force panel; the example below changes the defaultLength of a SpringForce from DEFAULT_SPRING_LENGTH to 42.

ForceDirectedLayout fdl = new ForceDirectedLayout("graph");
ForceSimulator fs = new ForceSimulator();
fs.addForce(new NBodyForce());
fs.addForce(new DragForce());
fs.addForce(new SpringForce(DEFAULT_SPRING_COEFF, 42));
fdl.setForceSimulator(fs);

Alternatively, update the SpringForce directly, as shown here.

ForceDirectedLayout fdl = new ForceDirectedLayout("graph");
ForceSimulator fs = fdl.getForceSimulator();
Force[] forces = fs.getForces();
SpringForce sf = (SpringForce) forces[2];
sf.setParameter(SPRING_LENGTH, 42);