A sketching interface for terrain modeling

Three-dimensional terrain models are widely used in entertainment applications such as movies and video games. These terrain models are mainly used as background and it is not necessary to carefully design every detail. A popular interface for designing terrain models is standard polygonal mesh editing that explicitly manipulates 3D positions of vertices. Another popular approach is to paint 2D heightfield, from which the system generates a corresponding mesh [Terragen]. These interfaces are suitable for careful design by experts, but not necessarily easy or intuitive for casual users. The Harold system [Cohen et al. 2000] included an interface where the user can directly sketch the ridgeline to design hills and mountains, but the resulting terrain looks awkward when viewed from other viewpoints.