Journal of Geo-information Science >
An Efficient Analogy Scheme of Hemispherical Photography Method under High-reality Virtual Forest Environment
Received date: 2013-01-04
Revised date: 2013-02-19
Online published: 2013-06-17
Hemispherical photography method was widely used in the measurement of structural parameters and photosynthetically active radiation of vegatation canopies. The simulation of hemispherical photography method under high-reality virtual forest environment can be used to evaluate the measurement precision of hemispherical photography method quantitatively and used as a useful tool for ground based validation. But there are some difficulties faced for the analogy of hemispherical photography method under high-reality virtual forest environment, such as the highly complex of scene, huge number of triangles, the distribution model of trees, and the low efficiency of simulation etc. In this study, a library of virtual forest scenes with characteristics of different stand density, the distribution mode of tree, size, species etc. was build first based on the principle of the establishment of high-reality virtual forest environment, and then, a comparative analysis between four different splitting plane search methods (such as spatial median algorithm, object median algorithm, heuristic ordering algorithm and heuristic BIN zoning algorithm) was carried out based on the ray tracing and hemispherical photography analogy methods. Results show that the heuristic ordering algorithm is the best choice for the analog of hemispherical photography method as compared to the other three splitting plane search methods. At last, the efficiency of the organization of data sets at two scales of isolated tree model and virtual forest scene for four data structures was comparative analyzed based on the library of high reality of virtual forest environment. A list of parameters was used as the indicator to evaluate the performance of the four data structures, such as the number of the ergodic nodes of scene, the number of the ergodic nodes of isolated tree model, the ergodic number of isolated trees, the number of ergodic triangles and the average compute time etc. Results show that the data structure of Kdtree was superior to the other three data structures. In the end, we can draw conclusion that the unity of heuristic ordering algorithm and Kdtree data structure is the best choice for the analog of hemispherical photography method under high reality virtual forest environments.
GAN Long-Fei, JU Jie, TANG Li-Yu, CHEN Chong-Cheng, HUANG Hong-Yu . An Efficient Analogy Scheme of Hemispherical Photography Method under High-reality Virtual Forest Environment[J]. Journal of Geo-information Science, 2013 , 15(3) : 345 -355 . DOI: 10.3724/SP.J.1047.2013.00345
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