Symbolic Representation of Vector Map in Virtual Geographic Environment

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Those basic geometric graphs such as lines and polygons are the main representations used by 3D rendering methods of vector map at present. It is so simple that strictly limited map feature information has been transferred. Consequently, an extended rendering method based on the shadow volume stencil theory is presented, which allows real time symbolical overlay of vector map on terrain. Firstly, the basis of vector data visualization based on stencil shadow volume theory has been reviewed. Secondly, in order to improve visualization effect, the cartographic symbolization of vector map, i.e. roads, has been dedicated, which includes smooth border with rounded caps, outlines and overlaps. Finally, the experiment shows that real time displaying of vector map on terrain has been achieved, and the visualization effects have been improved by cartographic symbolical overlay.

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With the extensive application of virtual geographic environments and the rapid development of 3D visualization analysis, the rendering of complex vector lines has attracted significant attention. Although there are many rendering algorithms in 3D geographic information system (GIS), they are not sufficiently flexible to meet the requirements for rendering linear symbols composed of diverse colors and shapes. However, the interactive rendering of a scene and the accuracy of the symbols are important components for large-scale, complex vector lines. In this paper, we propose a graphics processing unit (GPU)-accelerated algorithm for rendering linear symbols on 3D terrain. Symbol rendering is embedded within the terrain-rendering process, and vector lines are encoded in a 3D texture and then transferred to the GPU. A set of visual properties are used to enrich the expression of symbols with the help of geometric operations in the fragment shader. A series of experiments demonstrate that the proposed method can be utilized for drawing various pixel-exact linear symbols and can achieve real-time rendering efficiency.
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In this paper we present a hybrid technique that is capable of precisely and efficiently overlaying 2d geo-spatial vector data on a 3d multiresolution terrain model. The first part of this hybrid technique is a texture-based approach that is especially suited for applications that demand high flexibility since it allows the modification of the vector data through user input in real-time. This is faciliated by an efficient method to generate textures on-the-fly in an offscreen buffer. Quality superior to standard texture mapping is achieved by using a perspective reparameterization similar to that applied in perspective shadow mapping. The second part is a geometry-based approach that is addressed to applications focused on high quality visualizations. In a preprocessing step 3d geometry is created from the 2d vector data for each level-of-detail of the terrain and completely incorporated into the terrain quadtree hierarchy. The combination of the two approaches in one terrain rendering framework enables the user to choose the method according to his demands and to benefit from the advantages of both techniques.
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Interactive three-dimensional (3D) visualization of very large-scale grid digital elevation models coupled with corresponding high-resolution remote-sensing phototexture images is a hard problem. The graphics load must be controlled by an adaptive view-dependent surface triangulation and by taking advantage of different levels of detail (LODs) using multiresolution modeling of terrain geometry. Furthermore, the display of vector data over the level of detail terrain models is a challenging task. In this case, rendering artifacts are likely to occur until vector data is mapped consistently and exactly to the current level-of-detail of terrain geometry. In our prior work, we have developed a view-dependent dynamic block-based LOD mesh simplification scheme and out-of-core management of large terrain data for real-time rendering on desktop PCs. In this paper, we have proposed a new rendering algorithm for the combined display of multiresolution 3D terrain and polyline vector data representing the geographical entities such as roads, state or country boundaries etc. Our algorithm for multiresolution modeling of vector data allows the system to adapt the visual mapping without rendering artifacts to the context and the user needs while maintaining interactive frame rates. The algorithms have been implemented using Visual C++ and OpenGL 3D API and successfully tested on different real-world terrain raster and vector data sets.
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The efficient and high quality rendering of complex road networks—given as vector data—and high-resolution digital elevation models (DEMs) poses a significant problem in 3D geographic information systems. As in paper maps, a cartographic representation of roads with rounded caps and accentuated clearly distinguishable colors is desirable. On the other hand, advances in the technology of remote sensing have led to an explosion of the size and resolution of DEMs, making the integration of cartographic roads very challenging. In this work we investigate techniques for integrating such roads into a terrain renderer capable of handling high-resolution data sets. We evaluate the suitability of existing methods for draping vector data onto DEMs, and we adapt two methods for the rendering of cartographic roads by adding analytically computed rounded caps at the ends of road segments. We compare both approaches with respect to performance and quality, and we outline application areas in which either approach is preferable.
The hybrid geometry information system which can process vector and terrain data at the same time has become a hot. And one of the key problems is how to render complex vector data over multi-resolution terrain. A key data structure and associated algorithm for the combined display of multi-resolution 3D terrain and 2D curve feature were proposed. Then a performance analysis was made and a conclusion is given.
In the 3D geographic information systems (GIS), it is necessary to overlay 2D vector data on a 3D multi-resolution terrain model. This paper presents a precise and efficient texture-based overlaying algorithm. It generates vector textures from cascaded view-depended cameras to improve the utilization of texture pixels. The strategies of both depth splitting and screen space dividing are further adopted. All steps are based on programmable GPU pipeline. It runs in real-time and is suitable for displaying large-scale terrain with LOD algorithms.
The most commonly used topographic vector data, the reference data of national geographic information systems (GIS) are currently two-dimensional. The topography is modelled by different objects which are represented by single points, lines and areas with additional attributes containing information, for instance on the function and size of the object. In contrast, a digital terrain model (DTM) in most cases is a 2.5D representation of the earth's surface. The integration of the two data sets leads to an augmentation of the dimension of the topographic objects. However, due to inconsistencies between the data the integration process may lead to semantically incorrect results.This paper presents a new approach for the integration of a DTM and 2D GIS vector data including the re-establishment of the semantic correctness of the integrated data set. The algorithm consists of two steps. In the first step the DTM and the topographic objects are integrated without considering the semantics of the objects. This geometric integration is based on a DTM TIN (triangular irregular network) computed using a constrained Delaunay triangulation. In the second step those objects which contain implicit height information are further utilized: object representations are formulated and the semantics of the objects are considered within an optimization process using equality and inequality constraints. The algorithm is based on an inequality constrained least squares adjustment formulated as the linear complementary problem (LCP). The algorithm results in an integrated semantically correct 2.5D GIS data set.Results are presented using simulated and real data. Lakes represented by horizontal planes with increasing terrain outside the lake and roads which are composed of several tilted planes were investigated. The algorithm shows satisfying results: the constraints are fulfilled and the visualization of the integrated data set corresponds to the human view of the topography.
This paper presents a texture-based algorithm for vector data display that is able to precisely and efficiently overlay traditional 2D vector data on a 3D multi-resolution terrain model. By the algorithm, depending on the view to the scene first, a perspective projection is created, to match the currently visible range of the terrain. Then the projection is used to generate the texture on-the-fly with the texture coordinates calculated on GPU. The quality superior to standard texture mapping can be achieved by using the view-dependent perspective projection, for improving the availability ratio of texture pixels. In addition, since the algorithm is independent of the underlying terrain geometry, it is suited to work with terrain LOD algorithms and image pyramid.
Shadows are advocated for improved comprehension and enhanced realism in computer-synthesized images. A classification of shadow algorithms delineates three approaches: shadow computation during scanout; division of object surfaces into shadowed and unshadowed areas prior to removal of hidden surfaces; and inclusion of shadow volumes in the object data. The classes are related to existing shadow algorithms and implementations within each class are sketched. A brief comparison of the three approaches suggests that the last approach has the most appealing characteristics.
In geographical information systems (GIS) vector data has important applications in the analysis and management of virtual landscapes. Therefore, methods that allow combined visualization of terrain and geo-spatial vector data are required. Such methods have to adapt the vector data to the terrain surface and to ensure a precise and efficient mapping. In this paper, we present a method that is based on the stencil shadow volume algorithm and allows high-quality real-time overlay of vector data on virtual landscapes. Since the method is a screen-space algorithm it is per-pixel exact and does not suffer from aliasing artifacts like texture-based techniques. In addition, since the method is independent of the underlying terrain geometry, its performance does not depend on the complexity of the data set but only on the complexity of the vector data.
Previous research on the Virtual Geographic Environment (VGE) has focused mainly on representation rather than geographic analysis. However, geographic analysis plays a significant role in modern geography. To address this issue, this paper systematically examines theories and implementing VGE techniques that support geographical analysis and simulation. Based on its framework, VGE can be divided into four subtypes. These are the data environment, modeling environment, expression environment, and collaborative environment. The functions and key techniques of each are examined, and some case studies are discussed. This study provides direction for necessary new developments of advanced VGE platforms. KeywordsVGE–data environment–modeling environment–expression environment–collaborative environment
Conference Paper
Vector data represents one major category of data managed by GIS. This paper presents a new technique for vector-data display that is able to precisely and efficiently map vector data on 3D objects such as digital terrain models. The technique allows the system to adapt the visual mapping to the context and user needs and enables users to interactively modify vector data through the visual representation. It represents a basic mechanism for GIS interface technology and facilitates the development of visual analysis and exploration tools.
Conference Paper
Modern desktop PCs are capable of taking 2D Geographic Information System (GIS) applications into the realm of interactive 3D virtual worlds. In prior work we developed and presented graphics algorithms and data management methods for interactive viewing of a 3D global terrain system for desktop and virtual reality systems. In this paper we present a key data structure and associated render-time algorithm for the combined display of multi-resolution 3D terrain and traditional GIS polyline vector data. Such vector data is traditionally used for representing geographic entities such as political borders, roads, rivers and cadastral information.
We present a method to populate very large terrains with very detailed features such as roads, rivers, lakes and fields. These features can be interactively edited, and the landscape can be explored in real time at any altitude from flight view to car view. We use vector descriptions of linear and areal features, with associated shaders to specify their appearance (terrain color and material), their footprint (effect on terrain shape), and their associated objects (bridges, hedges, etc.). In order to encompass both very large terrains and very fine details we rely on a view dependent quadtree refinement scheme. New quads are generated when needed and cached on the GPU. For each quad we produce on the GPU an appearance texture, a footprint texture, and some object meshes, based on the features vector description and their associated shaders. Adaptive refinement, procedural vector features and a mipmap pyramid provide three LOD mechanisms for small, medium and large scale quads. Our results and attached video show high performance with high visual quality.
Ground Feature and Terrain Merging Arithmetic and Accuracy Evaluation
  • L Ning
  • L. Ning
Terrain Matching for Three-dimensional Visualization of Two-dimensional GIS Vector Data
  • L Kang
  • J Zhao
  • H.-C Song
  • L. Kang
Research on the Multi-Resolution Modeling and Three-Dimensional Display of GIS Vector Data
  • B Yang
  • L Kang
  • L Wu
  • B. Yang
Study on Urban Environment Procedural Modeling Techniques
  • L Wang
The Organization Management and 3D Visualization of Vector Data based on Geographic Information Grid
  • X Cao
  • X. Cao
Visualization in Geo-Spatial Data
  • J Gao
  • J. Gao
Efficient and accurate rendering of vector data on virtual landscapes
  • M Schneider
  • M. Schneider
High-Quality Cartographic Roads on High-Resolution DEMs
  • M Vaaraniemi
  • M Treib
  • M. Vaaraniemi