The two main modeling techniques are sketch-based modeling and procedural modeling. Procedural modeling is a better approach for modeling more detailed features such as terrain whereas sketch-based modeling can provide higher control over the desired output. We present a framework that combines both of these techniques to make a 3D geometric model of a terrain, such as a mountain range, from minimal user input. The user is required to sketch the silhouette strokes representing the ridgelines of terrain.
In the first phase we analyze the 2D user-sketched silhouettes and extract constraints on the height values of some positions on the landscape. Then we estimate depth values and profile slopes of these positions. In the second phase we apply the path planning procedural technique to generate a heightmap that fits the constraints. The main advantage of path planning over the other procedural methods is that it can add sharp ridges and irregular curves that we need in order to add detailed features to the smooth sketch based model. In subsequent work we plan to further explore and refine the hybrid modeling approach for terrain synthesis.