3D Distribution Simulation Of Virtual Plant Canopy Photosynthetic Active Radiation Based On Radiosity

The rapid development of computer hardware and software has promoted the in-depth study of virtual plant, thereupon, the research of the distribution of the plant canopy Photosynthetic Active Radiation (Photosynthetic Active Radiation, PAR) has been paid more and more attention. Photosynthetic Active Radiation distribution within the plant canopy is three-dimensional, and it changes quite actively under the influence of surrounding factors. With the aid of Computer Geometric Modeling technology, we can generate sophisticated high fidelity 3D plant model quickly, what’s more, the use of lighting model from computer graphics can be effective in studying the three-dimensional distribution of Photosynthetic Active Radiation within virtual plant canopy and its acquisition capability. This paper is based on Radiosity, taking loquat for example, it simulates the 3D spatial distribution of the single virtue plant canopy in both direct sunlight PAR and sky scattering PAR, and analyzes the interception ability of the canopy from two loquat varieties among different moment of one day. The specific contents of this paper are as follows:(1) To summarize the current research and present situation of the virtual plant modeling and the simulation of Photosynthetic Active Radiation distribution within virtue plant canopy both at home and abroad, and to analyzes and compare the mainstream technology which used in simulating Photosynthetic Active Radiation distribution within virtue plant canopy in detail.(2) Taking national fruit trees in fuzhou loquat germplasm nursery 7 years wooden luo loquat and red evening as an example, I base the study on field investigation and measured data, and combine the study with the knowledge of Plant Architecture to analyze morphological structure characteristics of loquat, and I use 3D Studio Max to build the 3D model of these leaves,and then make use of the interactive single tree geometric modeling tools, ParaTree, to establish fine single tree three-dimensional model of loquat, which makes the foundation of radiation simulation.(3) Based on the theory of Radiosity, I put forward the technology processes of the simulation of Photosynthetic Active Radiation distribution within virtual plant canopy, and make the use of Hemi-Cube algorithm to calculate the form factors of Radiosity, and I take the advantage of the Sutherland-Hodgman polygon clipping algorithm to improve the efficiency of the form factors determination, and I choose the Progressive Refinement iterative method for solving the Radiositiy linear equations. I exploit the module of Photosynthetic Active Radiation simulation within virtue plant canopy based on Radiosity, and I have integrated it with the interactive single tree geometric modeling tools, ParaTree, which is researched and developed by our research group seamlessly, and with it,’the radiosity and the flux of each element of the surface of the virtue plant model can be culculated. Take the wooden luo loquat and red evening loquat as example, we can simulate the three-dimensional distribution of sky scattering PAR and direct sunlight PAR within the virtual plant canopy, and analyze the accuracy of form factors on Radiositiy.I take the wooden luo loquat and red evening loquat as the simulation object, and based on the Radiosity model to establish the technology process of simulating virtue plant canopy Photosynthetic Active Radiation distribution.(4) I have compared and analyzed the Photosynthetic Active Radiation interception capability of wooden luo loquat and red evening loquat model canopy among nine times in one day, and I have compared the result with its counterpart which is obtained by the using ray tracing model to simulate the type of direct sunlight and the tortoise algorithm to simulate the sky scattering respectively, which turns out that the data that is based on different algorithms has a good consistency. The data show that the total canopy of wooden luo loquat instantaneously intercepts more PAR energy, nevertheless, it has a thicker leaf canopy layer, which results that Photosynthetic Active Radiation can not reach inside the canopy, and which leads to more invalid light district in the canopy, in this case, the average net photosynthetic rate of wooden luo loquat is lower.