基于器官尺度虚拟玉米冠层直射光分布的快速计算模型

为了给精确农业研究中所需的植物冠层光分布快速计算提供解决方法，提出了一个基于虚拟相机的玉米冠层直射辐射分布快速计算模型。该模型主要包括一个能代表田间玉米植株群体空间结构特征的虚拟冠层和一个虚拟相机，采用虚拟相机从太阳入射方向拍摄冠层图像，通过图像判读计算出植株各器官的太阳直射辐射分布。从模拟精度与模拟时间两方面评估了该模型的有效性。结果表明，该模型能很好地模拟器官尺度的植株光分布，并且比现有模型明显地缩短了计算时间。在引入计算虚拟冠层最小复制植株数的算法后，该模型的计算时间还能进一步缩短。另外，还探讨了虚拟冠层的植株器官形态简化描述的可行性，结果表明过度简化会导致模拟误差的明显增加。

Efficient model for computing the distribution of direct solar radiation in maize canopy at organ level

An efficient model for computing the distribution of direct solar radiation in a maize canopy was developed. A virtual camera and a virtual canopy were used to complete the simulation at organ level, in which plant organ types were labeled by different colors. The virtual camera was used to take pictures of the virtual canopy from solar incident direction, with orthographic projection. The images were then used to compute the light distribution among individual plant organs by counting pixel numbers of each color type. The validities of the simulation results were evaluated from two aspects: simulation accuracy and computing time. The results showed that the simulation results agreed satisfactorily with those produced by a projection Z-buffer model(PZB) which had been validated by field experiments, but the computing time was much shorter than PZB model, and then was further decreased when introducing an algorithm to compute the minimum number of copied plants around the studied plant stand. Furthermore, the feasibility of simplifications of plant organs was discussed. The results showed that excessive simplifications resulted in increasing the simulation errors noticeably.