A Realistic Structure Model for Forest Radiosity Simulation on Large Scales

Huaguo Huang 1, 2, Min Chen 1, Qinhuo Liu 1, Qiang Liu 1, Yang Zhang 1 and Wenhan Qin 1 +
1 State Key Laboratory of Remote Sensing Science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University, 100101, Beijing, P.R. China
2 Key Laboratory for Silviculture and Conservation, Ministry of Education; College of Forestry, Beijing Forestry University, 100083, Beijing, P.R. China

Abstract. The Radiosity-Graphics Model (RGM) is an important branch of computer simulation models for vegetation BRDF. Because the radiosity method is based on a global solving technique and computers’ computation capability is limited, RGM can not run beyond a limitation of the number of polygons in a scene (estimated as 500,000 for a normal  PC). Therefore, RGM was only used for small-scale scenes such as farmland, lawn or homogeneous forest. However, it is common that the land is rugged in nature, so the main work of this paper is to extend RGM to simulate  forest radiosity on a complex topography and put simulations of large-scale forest scenes into practice. Based on RGM, we focus on the methods to construct a large-scale virtual forest scene and use a scene division method to simulate large-scale forest radiosity on complex topographic conditions. Our work can be described as follows: (1) Virtual forest scene generation combined with DEM. (2) Scene division: We realize a scene-division method by correcting shading effects of the sub-scenes and considering multiple scattering. (3) BRF of the whole scene: We realize an algorithm to merge simulation results from all the divided sub-scenes and calculate the BRF of the whole scene. (4) Evaluation and application: By comparing the sub-scene method with the original RGM model in a relative small scene, the code is confirmed to be correct. By applying our new model to a conifer forest scene on a GUASS terrain from RAMI3 (http://rami-benchmark.jrc.it), we make sure of the rationality of our simulation results. The application supply the gap that RGM is  absent of large-scale scene simulations in RAMI3. Although good results have been achieved, some limitation and errors of the scene division method are also discussed in the paper. In addition, the future research direction is proposed.

Keywords: RGM, large scale, BRDF, scene division

In: Wan, Y. et al. (eds) Proceeding of the 8th international symposium on spatial accuracy assessment in natural resources and environmental sciences, World Academic Union (Press).

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