User Control of Force-directed Layouts

Force-directed layouts are typically used for minimizing overlaps in node-link graphs. This can make it easier to interpret and derive meaning from the resulting visualization. Once such a layout is put in motion, however, the person interacting with it has little control over the "final" layout. This paper describes an approach that puts even inexperienced users in charge of force-directed layouts that are not limited to network diagrams. The visual interface to a powerful but relatively easy to use visualization grammar has been augmented with sliders for controlling the strength of constraints applied to visual objects. Users can change the balance of power between constraints while the visualization is running, specify different constraints for groupings of visual objects, turn off all or some of the constraints affecting the layout, or return a layout to its pre-constraintsolving specification. This approach is a step towards addressing the need for tools with which all users can control and interact with force-directed layouts.