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A rapid visualization method of vector data over 3D terrain
Abstract
A rapid visualization method of GIS vector data on 3D terrain is proposed in this paper, including the organization of 3D vector data based on a quad-tree structure, the way to spatialize 2D vector data with terrain matching and methods to render a large amount of vector objects in a 3D scene. In the preprocessing procedure, vector data is extracted into different levels of detail using a simplification algorithm and then divided into quad-tree tiles. In the tile, a rapid terrain matching method is introduced to make 3D vectors go with terrain mesh faces. At run-time, vector objects are cached and managed by an object pool to realize rapid visualization. Experimental results prove the proposed method is a practical and efficient way to visualize large-scale vector data over 3D terrain.
... Texture-based approaches rasterize the vector data into textures that are then mapped onto the terrain surface [56]. Geometry-based approaches (often used for the simultaneous representation of digital elevation data and vector data [52,57,58,59,60]) allow the geometry of the vector data to exist separately from the geometry of the terrain, albeit modified for consistency with the terrain shape [61]. Shadow volume-based approaches, such as that described in [51], extrude the vector geometry into polyhedrons that are then rendered into the stencil buffer to distinguish between visible and invisible parts of the scene. ...
The creation of a digital representation of the Earth and its associated data is a complex and difficult task. The incredible size of geospatial data and differences between data sets pose challenges related to big data, data creation, and data integration. Advances in globe representation and visualization have made use of Discrete Global Grid Systems (DGGSs) that discretize the globe into a set of cells to which data are assigned. DGGSs are well studied and important in the GIS, OGC, and Digital Earth communities but have not been well-introduced to the computer graphics community. In this paper, we provide an overview of DGGSs and their use in digitally representing the Earth, describe several current Digital Earth systems and their methods of Earth representation, and list a number of applications of Digital Earths with related works. Moreover, we discuss the key research areas and related papers from computer graphics that are useful for a Digital Earth system, such as advanced techniques for geospatial data creation and representation.
... What is more, this approach can better support interactive operation and spatial analysis since it keeps the original properties of vector data. Thus, the geometry-based approach has been widely used by researchers (Agrawal, Radhakrishna , and Joshi 2006; Bruneton and Neyret 2008; Qiao et al. 2011; Schilling, Basanow, and Zipf 2007; Schneider, Guthe, and Klein 2005; Sun et al. 2010). However, the research has mainly aimed at linear vector rendering, and has barely dealt with polygonal vector rendering. ...
This study proposes a virtual globe-based vector data model named the quaternary quadrangle vector tile model (QQVTM) in order to better manage, visualize, and analyze massive amounts of global multi-scale vector data. The model integrates the quaternary quadrangle mesh (a discrete global grid system) and global image, terrain, and vector data. A QQVTM-based organization method is presented to organize global multi-scale vector data, including linear and polygonal vector data. In addition, tile-based reconstruction algorithms are designed to search and stitch the vector fragments scattered in tiles to reconstruct and store the entire vector geometries to support vector query and 3D analysis of global datasets. These organized vector data are in turn visualized and queried using a geometry-based approach. Our experimental results demonstrate that the QQVTM can satisfy the requirements for global vector data organization, visualization, and querying. Moreover, the QQVTM performs better than unorganized 2D vectors regarding rendering efficiency and better than the latitude-longitude-based approach regarding data redundancy.
Displaying polygonal vector data is essential in various application scenarios such as geometry visualization, vector graphics rendering, CAD drawing and in particular geographic, or cartographic visualization. Dealing with static polygonal datasets that has a large scale and are highly detailed poses several challenges to the efficient and adaptive display of polygons in interactive geographic visualization applications. For linear vector data, only recently a GPU‐based level‐of‐detail (LOD) polyline simplification and rendering approach has been presented which can perform locally‐adaptive LOD visualization of large‐scale line datasets interactively. However, locally optimized LOD simplification and interactive display of large‐scale polygon data, consisting of filled vector line loops, remains still a challenge, specifically in 3D geographic visualizations where varying LOD over a scene is necessary. Our solution to this challenge is a novel technique for locally‐optimized simplification and visualization of 2D polygons over a 3D terrain which features a parallelized point‐inside‐polygon testing mechanism. Our approach is capable of employing any simplification algorithm that sequentially removes vertices such as Douglas‐Peucker and Wang‐Müller. Moreover, we generalized our technique to also visualizing polylines in order to have a unified method for displaying both data types. The results and performance analysis show that our new algorithm can handle large datasets containing polygons composed of millions of segments in real time, and has a lower memory demand and higher performance in comparison to prior methods of line simplification and visualization.
Visualization of large vector line data is a core task in geographic and cartographic systems. Vector maps are often displayed at different cartographic generalization levels, traditionally by using several discrete levels‐of‐detail (LODs). This limits the generalization levels to a fixed and predefined set of LODs, and generally does not support smooth LOD transitions. However, fast GPUs and novel line rendering techniques can be exploited to integrate dynamic vector map LOD management into GPU‐based algorithms for locally‐adaptive line simplification and real‐time rendering. We propose a new technique that interactively visualizes large line vector datasets at variable LODs. It is based on the Douglas‐Peucker line simplification principle, generating an exhaustive set of line segments whose specific subsets represent the lines at any variable LOD. At run time, an appropriate and view‐dependent error metric supports screen‐space adaptive LOD levels and the display of the correct subset of line segments accordingly. Our implementation shows that we can simplify and display large line datasets interactively. We can successfully apply line style patterns, dynamic LOD selection lenses, and anti‐aliasing techniques to our line rendering.
Many studies have been focused on rendering 2D vector elements on 3D terrain, and a series of algorithms have been proposed. Most of these algorithms struggle to provide a seamless overlay between vector elements and an irregular terrain surface. Despite their importance, the physical characteristics of vector elements are often ignored, which distorts the surface of vector elements. For example, if vector elements that represent roads and rivers are simply overlaid on terrain, the phenomena of uneven surfaces and rivers going uphill may occur because of elevation fluctuation. To correct these deficiencies, terrain should be modified according to the physical characteristics of vectors. We propose a local terrain modification method: First, the elevation of terrain covered by vector elements is recalculated according to vectors’ physical characteristics. Second, the multigrid method is used to realize a smooth transition between the modified terrain and its surrounding area. Finally, by setting different transition ranges and comparing the visualization effects, rules are given for the selection of a suitable range. After modification, the terrain conforms to vectors’ physical characteristics, and the overall relief is undamaged. The proposed method was applied to a CPU–GPU parallel heterogeneous model and demonstrated a high level of performance.
Virtual globes are technologies for visual navigation through a three-dimensional, multi-resolution model of the entire planet. Data representations used in virtual globes, however, lack geometric flexibility at high-resolution levels of the planet-wide terrain surface. This is a problem especially if boundaries between individual geospatial features and the terrain are important. A novel integration of individual polygonal boundaries with a specific multi-resolution representation of the planet-wide terrain is developed in this article. In the preparation stage, the integration relies on an original simplification algorithm applied to the polygonal boundaries between geospatial features and the terrain. Its output is a multiple level-of-detail (LOD) geometry, which can be combined with a known multi-LOD representation of the terrain that uses run-time triangulation. This data representation is suitable for storage in existing database systems, avoids any data redundancy across LODs, and is even independent of the subdivision schema that partitions the planet's surface for the sake of dealing with LODs. At run-time, a novel reconstruction algorithm stitches geometric parts from different LODs together in a manner that augments the multi-LOD representation of the terrain. Within a certain proximity range from a given position, the method reconstructs a scene that preserves topological relations between the boundaries of geospatial features with the terrain. The method also guarantees that certain nearest proximity to the given position consists of the best geometries that correspond to the original datasets. Such properties of the method close up the gap between a mere exploratory visualization of static, pre-generated models and the models supporting geospatial analysis, which is deemed crucial for applications in Geographic Information Systems, Building Information Modelling and other software industries. A prototype implementation and experiment results that prove this method are also presented.
Progressive transmission of raster images over the World- Wide Web has been successfully applied to provide the user with coarser versions of the data before downloading a complete image. On the other hand, in the vector domain progressive transmission is challenging. Increasing the level of detail of a vector dataset does not simply imply adding pixels to it. In this paper, we discuss issues related to the progressive transmission of vector maps. We also describe a model for multiple representations of maps that can be transmitted progressively.
We describe a terrain rendering algorithm for spherical terrains based o n clipmaps. It leverages the high geometry throughput of current GPU to render large static triangle sets. The vertic es are displaced by a height map texture. Our main contribution is mapping of texture coordinates to calculate the height map sample position based on the static vertex offset and the variable view position.
Edgebreaker is a simple scheme for compressing the triangle/vertex
incidence graphs (sometimes called connectivity or topology) of
three-dimensional triangle meshes. Edgebreaker improves upon the storage
required by previously reported schemes, most of which can guarantee
only an O(t log(t)) storage cost for the incidence graph of a mesh of t
triangles. Edgebreaker requires at most 2t bits for any mesh
homeomorphic to a sphere and supports fully general meshes by using
additional storage per handle and hole. For large meshes, entropy coding
yields less than 1.5 bits per triangle. Edgebreaker's compression and
decompression processes perform identical traversals of the mesh from
one triangle to an adjacent one. At each stage, compression produces an
op-code describing the topological relation between the current triangle
and the boundary of the remaining part of the mesh. Decompression uses
these op-codes to reconstruct the entire incidence graph. Because
Edgebreaker's compression and decompression are independent of the
vertex locations, they may be combined with a variety of
vertex-compressing techniques that exploit topological information about
the mesh to better estimate vertex locations. Edgebreaker may be used to
compress the connectivity of an entire mesh bounding a 3D polyhedron or
the connectivity of a triangulated surface patch whose boundary need not
be encoded. The paper also offers a comparative survey of the rapidly
growing field of geometric compression
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.
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.
Improving on Our ExplanationIntellectual Impact and LegacyFurther ReadingReferences
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.
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.
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.
3D terrain visualization is an important function in 3D GIS. Traditional methods emphasis on the real displaying of 3D terrain and its simplification, they ignore the analysis functions on the spatial data. This paper proposed a method that can display vector data on 3D terrain surface and we can make spatial analysis according to these vector data. Terrain surface is composed of DEM grids and every grid can be divided into two triangles. The vector data rendered on terrain can be considered as a part of the triangles. Given that a 2D point which including (x,y) information, we can get the third dimension information by spatial interpolation. Then we can draw arcs and polygons on terrain surface based on these 3D point data. It must adopt special methods to avoid the vector data displaying above or below the terrain surface. When drawing arcs on terrain surface, we tried out all intersection points between arc lines and triangles' edges so as to ensure the arc cling on the surface. When drawing polygons on terrain surface, we designed a recursive algorithm to connect local triangular nets for the 3D polygon so that the polygon can cling on the surface too. Finally, the author applied this method on the visualization of 3D terrain of JingJiang regions of China and obtained a good effect
Level-of-detail rendering is essential for rendering very large, detailed worlds in real-time. Unfortunately, level-of-detail computations can be expensive, creating a bottleneck at the CPU. This paper presents the CABTT algorithm, an extension to existing binary-triangle-tree-based level-of-detail algorithms. Instead of manipulating triangles, the CABTT algorithm instead operates on clusters of geometry called aggregate triangles. This reduces CPU overhead, eliminating a bottleneck common to level-of-detail algorithms. Since aggregate triangles stay fixed over several frames, they may be cached on the video card. This further reduces CPU load and fully utilizes the hardware accelerated rendering pipeline on modern video cards. These improvements result in a fourfold increase in frame rate over ROAM at high detail levels. Our implementation renders an approximation of an 8 million triangle height field at 42 frames per second with an maximum error of 1 pixel on consumer hardware.
The key to real-time rendering of large-scale surfaces is to locally adapt surface geometric complexity to changing view parameters. Several schemes have been developed to address this problem of view-dependent level-of-detail control. Among these, the view-dependent progressive mesh (VDPM) framework represents an arbitrary triangle mesh as a hierarchy of geometrically optimized refinement transformations, from which accurate approximating meshes can be efficiently retrieved. In this paper we extend the general VDPM framework to provide temporal coherence through the run-time creation of geomorphs. These geomorphs eliminate "popping" artifacts by smoothly interpolating geometry. Their implementation requires new output-sensitive data structures, which have the added benefit of reducing memory use. We specialize the VDPM framework to the important case of terrain rendering. To handle huge terrain grids, we introduce a block-based simplification scheme that constructs a progressive mesh as a hierarchy of block refinements. We demonstrate the need for an accurate approximation metric during simplification. Our contributions are highlighted in a real-time flyover of a large, rugged terrain. Notably, the use of geomorphs results in visually smooth rendering even at 72 frames/sec on a graphics workstation.
Research on the Multi-Resolut ion Modeling and Three-Dimensional Display of GIS Vector Data
- B Yang
- L Kang
- L Wu
- R Yu
Terrain Matching for Threedimensional Visualization of Two-dimensional GIS Vector Data
- L Kang
- J Zhao
- H Song
- L Wu
Study of Realization Method and Improvement of Douglas-Peucher Algorithm of Vector Data Compressing
- D Yang
- J Wang
- G Lv