Sketch-based steering in Visdom

Abstract

Natural phenomena like earthquakes or floods cannot be avoided or controlled by humans but ignoring them can be fatal. In order to understand their characteristics and behavior computer simulations can be used. The gained knowledge is used to find strategies and countermeasures to minimize the damage caused by such disasters.<br />Visdom is a modular integrated visualization system which is developed to support the analysis of flood simulations. It provides the ability to test different decisions made by the user for example the establishment of barrier arrangements. These alternative scenarios can be visualized and analyzed in order to find the solution which minimizes damage in the vicinity. For modifying the flood, the simulation parameters have to be varied. In Visdom, this has to be done by inserting numeric values into textfields or using sliders. In most cases, the system is intended to be used in time-critical situations where fast interaction and testing is required. Therefore a sketch-based interface is introduced into Visdom which should simplify and accelerate the modification of simulation parameters. This kind of interaction increases the productivity and efficiency of the whole work-flow due to its intuitive and straightforward usage. Since Visdom is based on a modular data-flow system, the new functionality is implemented within a new node. The so-called Spline Node provides methods to create and manipulate a spline. It requires the drawn user input points which are captured by a view node. Due to the fact that Visdom is based on the data-flow concept, a new mechanism called Modular Interactors has to be introduced to enable interaction communication between nodes especially upstream.<br />In order to support the user during the sketching process the system provides visual feedback. The sketched stroke is represented using a tubular geometry which is directly visualized in the 3D view. After the spline is constructed it has to be interpreted to trigger commands which influence the simulation. For this issue two additional nodes are introduced. The Spline To Barrier Node is responsible for translating the sketch to a sandbag barrier or a mobile protection wall.<br />Manipulating the spline allows for changing the properties of the established barriers. The second interpretation possibility is implemented by the Spline To Force Node. It creates a force field according to the appearance of the spline which manipulates the fluid simulation directly. Also for this task visual feedback is essential which should provide information about the acting forces. Therefore a new render component is implemented which takes a vector field as input and generates an arrow plot. This component is also used to visualize the internal flow of the fluid.