Terrain Visualization

The real-time rendering of arbitrarily large textures is a problem that has long been studied in terrain visualization. For years, different approaches have been published that have either expensive hardware requirements or other severe limitations in quality, performance or versatility. The biggest problem is usually a strong coupling between geometry and texture, both regarding database structure, as well as LOD management.

We present a technique for efficient management of large textures and its real-time application to geometric models. The proposed technique is inspired by the clipmap [12] idea, that caches in video memory a subset of the texture mipmap pyramid. Based on this concept, we define some structures and a different management allowing its implementation on a personal computer without specific graphics hardware. Finally, we present the results of the application in a terrain visualization system, using several simultaneous textures with a detail up to 0.25 meters per texel, covering a 60,000 km 2 area.

We describe two experimental desktop library clients that offer improved access to geospatial data via the Alexandria Digital Library (ADL): ArcADL, an extension to ESRI's ArcView GIS, and vtADL, an extension to the Virtual Terrain Project's Enviro terrain visualization package. ArcADL provides a simplified user interface to ADL's powerful underlying distributed geospatial search technology. Both clients use the ADL Access Framework to access library data that is available in multiple formats and retrievable by multiple methods. Issues common to both clients and future scenarios are also considered.

Game engines are relatively low-cost but powerful systems for creating and exploring virtual environments, and are increasingly used in the fields of architecture and urban planning. Traditionally urban planners and landscape architects used small-scale hand-modelled terrains. However, in order to increase both realism and modelling efficiency it is preferable to use computer generated terrains obtained from remote sensing data. Unfortunately many game engines are designed to use relatively small infinitely repeating terrain blocks. In this paper we analyse how the popular Torque terrain engine, which is used by the Department of Architecture of the University of Auckland, can be modified and extended for architectural purposes. The ultimate limitations of the terrain engine are identified and the terrain engine is evaluated on its suitability for architectural design. We explain how large scale terrains can be incorporated into the engine design and we propose a way to integrate th...

In this paper we present a novel approach for interactive rendering of large terrain datasets. Our approach is based on subdividing a terrain into rectangular patches at different resolutions. Each patch is represented by four triangular tiles that are selected form different resolutions, and four strips which are used to stitch the four tiles in a seamless manner. Such a scheme maintains resolution changes within patches through the stitching strips, and not across patches. At runtime, these patches are used to construct a level-of-detail representation of the input terrain based on view-parameters. A selected level of detail only includes the layout of the patches and their boundary edges resolutions. The layout includes the location and dimension of each patch. Within the graphics hardware, the GPU generates the meshes of the patches by using scaled instances of cached tiles and assigns elevation for each vertex from cached textures. Since adjacent rectangular patches agree on the resolution of the common edges, the resulted mesh does not include cracks or degenerate triangles. Our algorithm manages to achieve quality images at high frame rates while providing seamless transition between different levels of detail.

There is extensive knowledge on how to represent terrain using various relief depiction methods, such as hill shading and cliff drawing in cartographic products using large-scale maps. However, the relevance and correct use of topographic information nowadays in small-scale maps does not seem to be of high priority. This information that is frequently poorly depicted in such products can be

We present an elegant and simple to implement framework for performing out-of-core visualization and view-dependent refinement of large terrain surfaces. Contrary to the recent trend of increasingly elaborate algorithms for large-scale terrain visualization, our algorithms and data structures have been designed with the primary goal of simplicity and efficiency of implementation. Our approach to managing large terrain data also departs from more conventional strategies based on data tiling. Rather than emphasizing how to segment and efficiently bring data in and out of memory, we focus on the manner in which the data is laid out to achieve good memory coherency for data accesses made in a top-down (coarse-to-fine) refinement of the terrain. We present and compare the results of using several different data indexing schemes, and propose a simple to compute index that yields substantial improvements in locality and speed over more commonly used data layouts.

Our second contribution is a new and simple, yet easy to generalize method for view-dependent refinement. Similar to several published methods in this area, we use longest edge bisection in a top-down traversal of the mesh hierarchy to produce a continuous surface with subdivision connectivity. In tandem with the refinement, we perform view frustum culling and triangle stripping. These three components are done together in a single pass over the mesh. We show how this framework supports virtually any error metric, while still being highly memory and compute efficient.

The real-time rendering of arbitrarily large textures is a problem that has long been studied in terrain visualization. For years, different approaches have been published that have either expensive hardware requirements or other severe limitations in quality, performance or versatility. The biggest problem is usually a strong coupling between geometry and texture, both regarding database structure, as well as LOD

We present a technique for efficient management of large textures and its real-time application to geometric models. The proposed technique is inspired by the clipmap (12) idea, that caches in video memory a subset of the texture mipmap pyramid. Based on this concept, we define some structures and a different management allowing its implementation on a personal computer without specific

This paper is focused on the analysis of virtual representation of terrain through the web, and shows the steps to follow in order to put into practice a virtual interactive terrain visualization system. The recent developments of three-dimensional visualization systems can be naturally applied to terrain visualization targeted to the web, driving to a higher interaction level. Traditionally it has

The real-time rendering of arbitrarily large textures is a problem that has long been studied in terrain visualization. For years, different approaches have been published that have either expensive hardware requirements or other severe limitations in quality, performance or versatility. The biggest problem is usually a strong coupling between geometry and texture, both regarding database structure, as well as LOD management.

We present an elegant and simple to implement framework for performing out-of-core visualization and view-dependent refinement of large terrain surfaces. Contrary to the trend of increasingly elaborate algorithms for large-scale terrain visualization, our algorithms and data structures have been designed with the primary goal of simplicity and efficiency of implementation. Our approach to managing large terrain data also departs from more conventional strategies based on data tiling. Rather than emphasizing how to segment ...

We present an interactive, real-time mapping system for use with digital elevation models and remotely sensed multispectral imagery that aids geoscientists in the creation and interpretation of geologic/neotectonic maps at length scales of 10 m to 1000 km. Our system provides a terrain visualization of the surface of the Earth or other terrestrial planets by displaying a virtual terrain model

The article describes a method for object and terrain visualization by means of the combination of two algorithms, one for terrain data and one for objects. Our purpose is to generate, efficiently and rapidly, aerial images of terrain with objects such as houses, ...

Geographical Information Systems (GIS) and three dimensional (3D) World Wide Web (WWW) applications usage are on the rise. The demand for online 3D terrain visualization for GIS data has increased. Current users demand for more complex data which have higher accuracy and realism. This is aided by the emergence of geo-browsers in the market which provide free service and also cater for the commercialized market. Other new technology driving the market is the use of software such as CityGML, Virtual Reality Markup Language (VRML)/ Entensive 3D (X3D), geoVRML, and Keyhole Markup Language (KML). These technologies also play an important role for this new era of online 3D terrain visualization. The aim of this paper is to implement the online 3D terrain visualization for GIS data by using VRML technology and launching the system into three different web servers. The data used for this system are contour data and high resolution satellite image (QUICKBIRD) for Universiti Putra Malaysia (U...

Digital terrain models constitute the base of terrain visualization applications, used to visualize in an easy and powerful way a great quantity of information obtained from the terrain, such as occurs in virtual terrain visualization systems, used to know and enjoy land, training simulations, determination of visual impacts, etc. But these models can also be used as the base for