LOOPS: Locally Optimized Polygon Simplification

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

Terrender: A Web-Based Multi-Resolution Terrain Rendering Framework

Terrain rendering is a fundamental requirement when visualizing 3D geographic data in various research, commercial or personal ap- plications such as geographic information systems (GIS), 3D maps, simulators, and games. It entails handling large amounts of data for height and color as well as high-performance algorithms that can benefit from the parallel rendering power of GPUs. The main challenge is (1) to create a detailed renderable mesh using a fraction of the data that is most relevant to a specific camera position and orientation, and (2) to update this mesh in real time as the camera moves while keeping the transition artifacts low. Many algorithms have been proposed for adaptive adjustment of the level of detail (LOD) of large terrains. However, the existing web-based terrain rendering frameworks do not use state-of-the-art algorithms. As a result, these frameworks are prone to classic shortcomings of sim- pler terrain rendering algorithms such as discontinuities and limited visibility. We introduce a novel open-source web-based framework for rendering high quality terrains with adaptive LOD: Terrender. Terrender employs RASTeR, a modern LOD-based terrain rendering algorithm, while running smoothly with a limited bandwidth on all common web browsers, even on mobile devices. Finally, we present a thorough analysis of our system’s performance when the camera moves on a predefined trajectory. We also compare its performance and visual quality to another well-known framework