月面形貌仿真可以为嫦娥三号着陆前地形建立及视觉导航仿真测试提供逼真的三维月面环境。利用分形随机算法并结合月面撞击坑与石块的数学分布模型，在实现月面数字地形的基础上利用纹理映射和纹理融合的方法为月面地形添加纹理，完成了月面逼真三维环境的构建。结合导航相机的外方位元素和光照条件，实现了对该仿真月面环境的模拟环拍，支撑了嫦娥三号发射前月球车导航相机数据获取、地形建立、通行代价图计算、月球车路径规划等遥操作任务过程仿真测试。测试结果表明，仿真月面三维地形具有良好的视觉效果，满足了巡视器导航相机测试验证对精细月面地形和纹理的需求，为导航相机测试验证提供了有效的月面形貌仿真数据。
李巍, 孙义威, 万文辉, 刘召芹, 胡文敏, 岳宗玉, 邸凯昌, 苗毅, 詹磊
. 月面形貌仿真设计及在嫦娥三号任务中的应用[J]. 地理研究, 2014
, 33(6)
: 1040
-1048
.
DOI: 10.11821/dlyj201406005
Chang'E-3 rover is the first lunar rover launched by China National Space Administration. As the‘eyes’of the rover, the navigation cameras play a crucial role in mission operations of the rover on lunar surface. High-resolution DEMs and DOMs generated from navigation images using photogrammetric techniques can provide accurate terrain and location information for rover positioning and route planning. Simulation tests in experimental field before launch are necessary to ensure the effectiveness and reliability of the techniques and procedures. Computer simulation is undoubtedly a low-cost and efficient way to simulate the lunar terrain and environment in the early verification process of the navigation cameras. Using computer simulation, a variety of lunar terrain can be generated easily for verification of the measurements of the navigation cameras with the pre-defined parameters. In this paper, techniques of fine-scale lunar terrain simulation and texture simulation are studied for navigation camera verification. Lunar terrain simulation consists of lunar basic terrain simulation and lunar surface feature simulation. For basic terrain simulation, we first generate a rough terrain using random fractal algorithm, and then get a finer terrain from rough terrain using midpoint displacement method. For lunar surface feature simulation, 3D models of surface features, such as craters and rocks, are generated and placed on the basic terrain according to certain rules, and then they are merged to the terrain by modifying the raster terrain data, so that the terrain data can reflect the changes caused by the added feature models. For texture simulation, texture mapping and texture merging methods are used to generate terrain-consistent texture. Texture mapping creates textures based on the elevation values of each position and its neighbors in the terrain data. Texture merging generates local textures by Gaussian-weighted method using texture samples collected in advance. Lighting illumination is also added to the generated terrain by Open Scene Graph software. Finally, a realistic simulative lunar scene is generated and verification tests of the navigation cameras are performed according to the camera parameters and image acquisition instructions.
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