The Development Of Core Components For2-3D GIS Based On VTK

The2D&3D integration in GIS is a new technology, so the research on displaying2D and3D map using the same rendering engine on one platform is very significant. In this paper, we developed a set of2-3D GIS core components by using VTK as rendering system, the components can support both2D raster map, vector map and the3D terrain map. The whole process, including data preprocessing, data organization and storage, memory management, geographic data selection and real-time rendering, are all discussed in detail. The real-time rendering technology of2D raster map and3D terrain map is focused on in this paper.We put forward two pyramid cutting algorithms for different scale of input image during data preprocessing of raster map, then a quad-tree index is built and a memory buffer is managed for large scaled pyramid tiles so the tiles will be rendered in time with a limited memory.The research of3D terrain map is the most difficult part in our system. Blocked height-map, normal-map and texture-map are stored in a binary file to reduce the terrain data file number. In order to select terrain nodes by a given view frustum, we proposed a new LOD selection algorithm based on visual ranges of each LOD layer, which considering both the observer’s height and the terrain nodes’bounding box. For rendering terrain seamlessly, morph area is defined in each LOD layer’s view range, making a vertex in a higher complexity mesh morph into the lower one gradually, this method could be run in GPU very well.At last, we developed the whole system with every component as a module on the Goophy8.1platform, making it can be application developed by C++, C#and java. The experiments show that the system has good performance on the real-time rendering of large scaled2D vector map and3D terrain map.