This paper proposes an interactive risk visualization system to enable people to understand intuitively the risk of snow sliding from a roof. The system represents the risk as a colored bar and real-time computer graphics (CG) images simulated by the smoothed-particle hydrodynamic method (SPH). First, snow behavior is defined as fluid-based dynamics. Second, the risk is visualized in two ways with real-time CG of the snow sliding on a graphics processing unit (GPU). One is a colored bar along the ground where the snow hits, and another is numerical value for a zone where a viewer supposes to be safe from the snow sliding. Such visualization gives an intuitive understanding to the viewer. The viewer can interactively and graphically manipulate the conditions, such as the accumulated mass of snow, the pitch of the roof, and the zone where the viewer supposes to be safe. From the evaluation of the system on both aspects of intuitive understanding of the risk and usability, its effectiveness is especially shown to users who live in little snowfall regions and have few knowledge about the dangerous. Therefore, we conclude that the proposed system performs as a self-study tool about the safety from snow sliding.
