在使用OSGEarth三维地球引擎进行大规模地理空间数据可视化时,细节层次(Level of Detail,LOD)技术通过动态调整地形和模型的细节层次,在保证视觉质量的同时,显著降低了计算负载和资源消耗。但在分开叠加影像层与地形层在线服务数据时,...在使用OSGEarth三维地球引擎进行大规模地理空间数据可视化时,细节层次(Level of Detail,LOD)技术通过动态调整地形和模型的细节层次,在保证视觉质量的同时,显著降低了计算负载和资源消耗。但在分开叠加影像层与地形层在线服务数据时,由于两类数据服务层级精度不匹配,渲染时将出现白块、断层塌陷等视觉问题,文章提出了一种通过实时重采样自动创建子瓦片的方案,对影像图层与地形图层的精细层级不同的问题进行双线性重采样,有效解决白块和断层塌陷等现象,拥有良好的应用前景。展开更多
As starting point for patterns with seven-fold symmetry, we investigate the basic possibility to construct the regular heptagon by bicompasses and ruler. To cover the whole plane with elements of sevenfold symmetry is...As starting point for patterns with seven-fold symmetry, we investigate the basic possibility to construct the regular heptagon by bicompasses and ruler. To cover the whole plane with elements of sevenfold symmetry is only possible by overlaps and (or) gaps between the building stones. Resecting small parts of overlaps and filling gaps between the heptagons, one may come to simple parqueting with only a few kinds of basic tiles related to sevenfold symmetry. This is appropriate for parqueting with a center of seven-fold symmetry that is illustrated by figures. Choosing from the basic patterns with sevenfold symmetry small parts as elementary stripes or elementary cells, one may form by their discrete translation in one or two different directions periodic bordures or tessellation of the whole plane but the sevenfold point-group symmetry of the whole plane is then lost and there remains only such symmetry in small neighborhoods around one or more centers. From periodic tiling, we make the transition to aperiodic tiling of the plane. This is analogous to Penrose tiling which is mostly demonstrated with basic elements of fivefold symmetry and we show that this is also possible with elements of sevenfold symmetry. The two possible regular star-heptagons and a semi-regular star-heptagon play here a basic role.展开更多
文摘在使用OSGEarth三维地球引擎进行大规模地理空间数据可视化时,细节层次(Level of Detail,LOD)技术通过动态调整地形和模型的细节层次,在保证视觉质量的同时,显著降低了计算负载和资源消耗。但在分开叠加影像层与地形层在线服务数据时,由于两类数据服务层级精度不匹配,渲染时将出现白块、断层塌陷等视觉问题,文章提出了一种通过实时重采样自动创建子瓦片的方案,对影像图层与地形图层的精细层级不同的问题进行双线性重采样,有效解决白块和断层塌陷等现象,拥有良好的应用前景。
文摘As starting point for patterns with seven-fold symmetry, we investigate the basic possibility to construct the regular heptagon by bicompasses and ruler. To cover the whole plane with elements of sevenfold symmetry is only possible by overlaps and (or) gaps between the building stones. Resecting small parts of overlaps and filling gaps between the heptagons, one may come to simple parqueting with only a few kinds of basic tiles related to sevenfold symmetry. This is appropriate for parqueting with a center of seven-fold symmetry that is illustrated by figures. Choosing from the basic patterns with sevenfold symmetry small parts as elementary stripes or elementary cells, one may form by their discrete translation in one or two different directions periodic bordures or tessellation of the whole plane but the sevenfold point-group symmetry of the whole plane is then lost and there remains only such symmetry in small neighborhoods around one or more centers. From periodic tiling, we make the transition to aperiodic tiling of the plane. This is analogous to Penrose tiling which is mostly demonstrated with basic elements of fivefold symmetry and we show that this is also possible with elements of sevenfold symmetry. The two possible regular star-heptagons and a semi-regular star-heptagon play here a basic role.
