In this paper we present an example-based system for terrain synthesis. In our approach, patches from sample terrain (represented by a height field) are used to generate new terrain. The synthesis is guided by a user-sketched feature map that specifies where terrain features occur in the resulting synthetic terrain. Our system emphasizes large-scale curvilinear features (ridges and valleys) because such features are the dominant visual elements in most terrain. Both the example height field and user’s sketch map are analyzed using a technique from the field of geomorphology. The system finds patches from the example data that match the features found in the user’s sketch. Patches are joined together using graph cuts and Poisson editing. The order in which patches are placed in the synthesized terrain is determined by breadth-first traversal of a feature tree and this generates improved results over standard rasterscan placement orders. Our technique supports user-controlled terrain synthesis in a wide variety of styles, based upon the visual richness of real-world terrain data.

Multiresolution has been extensively used in many areas of computer science, including biometrics. We introduce local multiresolution filters for quadratic and cubic B-splines that satisfy the first and the second level of smoothness respectively. For constructing these filters, we use a reverse subdivision method. We also show how to use and extend these filters for tensor-product surfaces, and 2D/3D images. For some types of data, such as curves and surfaces, boundary interpolation is strongly desired. To maintain this condition, we introduce extraordinary filters for boundaries. For images and other cases in which interpolating the boundaries is not required or even desired, we need a particular arrangement to be able to apply regular filters. As a solution, we propose a technique based on symmetric extension. Practical issues for efficient implementation of multiresolution are discussed. Finally, we discuss some example applications in biometrics, including iris synthesis and volumetric data visualization. 1.

Abstract. Generating realistic-looking but interesting terrains quickly is a great challenge. We present RiverLand, an efficient system for terrain synthesis. RiverLand creates a realistic-looking terrain by first generating river networks over the land. Then, the terrain is created to be consistent with the river networks. In this way, the terrains created have a proper drainage basin, an important feature lacking in many existing procedural terrain methods. The terrains generated by RiverLand are also widely varied, with rolling hills, river valleys, alpine mountains, and rocky cliffs, all seamlessly connected in the same terrain. Since RiverLand does not use complex fluid simulations, it is fast, and yet is able to produce many of the erosion features generated by the simulation methods. 1

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Figure 1: As the user zooms in, terrain geometry is created to adaptively refine the planet. Realistic terrain models are required in many applications, especially in computer games. Commonly, procedural models are applied to generate the corresponding models and let users experience a wide variety of new environments. Existing algorithms generate landscapes immediately with view-dependent resolution and without preprocessing. Unfortunately, landscapes generated by such algorithms lack river networks and therefore appear unnatural. Algorithms that integrate realistic river networks are computationally expensive and cannot be used to generate a locally adaptive high resolution landscape during a fly-through. In this paper, we propose a novel algorithm to generate realistic river networks. Our procedural algorithm creates complete planets and landscapes with realistic river networks within seconds. It starts with a coarse base geometry of a planet without further preprocessing and user intervention. By exploiting current graphics hardware, the proposed algorithm is able to generate adaptively refined landscape geometry during fly-throughs.

We present a step toward interactive physics-based modeling of terrains. A terrain, composed of layers of materials, is edited with interactive modeling tools built upon different physics-based erosion and deposition algorithms. First, two hydraulic erosion algorithms for running water are coupled. Areas where the motion is slow become more eroded by the dissolution erosion, whereas in the areas with faster motion, the force-based erosion prevails. Second, when the water under-erodes certain areas, slippage takes effect and the river banks fall into the water. A variety of local and global editing operation is provided. The user has a great level of control over the process and receives immediate feedback since the GPU-based erosion simulation runs at least at 20 fps on off-the-shelf computers for scenes with grid resolution of 2048 × 1024 and four layers of material. We also present a divide and conquer approach to handle large terrain erosion, where the terrain is tiled, and each tile calculated independently on the GPU. We show a wide variety of erosion-based modeling features such as forming rivers, drying