| Ray tracing is a basic algorithm of computer graphics which was used for simulating the light propagation of real-world based on the principle of physical optics, it is not only widely used in gaming and film animation etc, but also can be used in agriculture, forestry and ecology etc. However, there are some limitations and disadvantages existed for the simulation of ray tracing under high-reality virtual forest environment, such as the high complexity of forest scenes, the huge number of triangles, and the low efficiency of simulation etc. In this study, a study of the acceleration schemeof ray tracingunder high-reality virtual forest environment was carried out based on datastructure and CUDA parallel methods. The main contents of this thesis are as following:(1) Three libraries of virtual forest scenes with different characteristics of stand density, the distribution mode of tree location, plot size, tree species of plotwere build based on the principle of the construction of high-reality isolated tree model and virtual forest environment.(2) A comparative analysis between four different splitting plane search methods (such as spatial median, object median, heuristic ordering and heuristic BIN zoning algorithms) was carried outand the time needed for the simulation ray tracing methods was choose as the factor of analysis.Results show that the ability tray racing of heuristic ordering algorithm is better than the other three splitting plane search methods. In addition, another comparative analysis was carried out upon two scales of data structure of isolated tree models and virtual forest scenes and ten kinds of scheme of data structure, such as traditional method, Kdtreeã€BVHã€Octree. And several factors were choose as the factor for analyzing, such as the number of ergodicnodes of scene, the number of ergodic nodes of isolated tree model, the ergodic number of isolated trees, the ergodic number of triangles and the average time needed for ray tracing etc. Results show that the data structure of Kdtree at two scales of forest scenes was superior to the other nine data structures.(3) The three-dimensional distribution of photosynthetically active radiation within forest scenes was archived based on ray tracing method and turtle algorithm. Study shows that the simulation accuracy of three-dimensional distribution of direct photosynthetically active radiation within virtual forest scenes was mainly influenced by the density of throw-in rays and the spatialdistribution of canopy components within three-dimensional space.Meanwhile, the simulation accuracy of three-dimensional distribution of diffuse photosynthetically active radiation of within virtual forest scenewas highly closed with the subdivision accuracy of hemisphere space.(4) A parallel simulation study of ray tracing under high-reality virtual forest environment was carried out based on CUDA parallel technique. After that, it applied to the simulation of hemispherical photography method and three-dimensional distribution of photosynthetically active radiation within virtual forest. Results show that simulationefficiency of ray tracing based on CUDA method was highly improved compared to traditional method. |
