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【目的】为了快速、准确地计算土体结构和孔隙度等特征,提出一种基于SFS算法(shape from shading)的土壤三维结构重构方法。【方法】首先获取土壤的灰度显微图像,根据朗伯表面漫反射模型建立土壤的光照方程;然后利用泰勒展开法和雅克比迭代法求解光照方程,计算出像素点高度值并实现土壤的三维重建;最后根据正态分布校正高度值计算土壤孔隙度。【结果】实验结果证明,该方法计算得出的孔隙度与环刀烘干法测得的结果相差0.81%,误差率1.75%。【结论】利用显微图像中土壤结构的三维信息,可以客观准确地计算出土壤孔隙度等物理特征。
【Objective】 In order to quickly and accurately calculate the characteristics of soil structure and porosity, a three-dimensional structure reconstruction method based on SFS (shape from shading) was proposed. 【Method】 Firstly, the grayscale microscopic image of soil was obtained, and then the illumination equation of soil was established according to the Lambertian surface diffuse reflection model. Then the Taylor equation and Jacobi’s iteration method were used to solve the illumination equation to calculate the pixel height and soil Three-dimensional reconstruction; Finally, according to the normal distribution of the corrected height value of soil porosity calculation. 【Result】 The experimental results show that the porosity calculated by this method is 0.81% and the error rate is 1.75%. 【Conclusion】 The physical characteristics of soil porosity can be objectively and accurately calculated by using the three-dimensional information of soil structure in microscopic images.