| Plants are one of the most important forms of life on earth,and most of them rely on photosynthesis for energy exchange.The leaves are the most important organs of plant photosynthesis and can directly reflect the growth status and appearance of plants.In recent years,with the continuous development of computer graphics,plant light transmission simulation,and agricultural remote sensing technology,the requirements for acquiring the optical characteristics of plant leaves have become higher and higher.However,the bidirectional reflectance distribution function(BRDF)of the plant leaf under light conditions must be obtained in order to acquire the optical characteristics of the plant leaf.BRDF is widely concerned by researchers in this field,but there are relatively few R&D facilities for its measurement equipment.The measurement equipment that has been developed has limitations and cannot be applied to the BRDF measurement of a type of material surface.Two special properties of material surface BRDF measurement.Moreover,the cost of the equipment is high,and the process of collecting data is complicated and takes a long time,requiring the operation of professionals.In this thesis,a new BRDF acquisition equipment was set up to obtain BRDF on the surface of plant leaves.The construction process was relatively simple and the measurement time only took 10 minutes,and no professional operation was required.Linear light sources are used instead of point light sources.Digital cameras replace industrial cameras.Computer-controlled single-axis motion controllers are used to precisely control the linear light source's movement speed in a single direction,resulting in 120 fixed viewing angles and constant changes in light source direction.The image collection of the blade,through the analysis and calculation of the serialized image of the blade,obtains the reflection trace,the diffuse reflection trace,and the highlight trace of the series of images,thereby further obtaining the apparent diffuse reflection,high light reflection,and roughness of the entire blade surface.Degree of the corresponding parameter.The main research contents and conclusions of the paper are as follows:(1)For the problem that the BRDF parameter acquisition equipment on the blade surface is expensive and the process is complex,a measurement device based on a linear light source is designed to obtain the BRDF parameters of the blade.The method controls the movement speed of the linear light source through a computer to control the uniaxial mover to provide a changinglight source for the photo of the plant leaf surface taken by the camera,thereby obtaining the sequence image of the leaf in a short time.(2)Construct a geometric model of the measuring device and calibrate the camera and calculate the BRDF parameters.By determining that the height of the photograph taken by the camera is 30 cm,the angle between the photographing angle and the vertical direction represents an angle of 55 degrees;the height of the linear light source is 15 cm,and the moving speed of the linear light source is 0.67 mm.Use OpenCV to perform camera checkerboard calibration and obtain the camera's internal and external reference matrix.According to the mathematical calculation model of Ward model,three important parameters of BRDF are obtained by Monte Carlo integration calculation,and the final experimental results are generated by GPU.(3)Comparing the real texture of the blade surface and the apparent texture of the blade drawn by the GPU in this experiment,it was found that the apparent BRDF parameters of the plant leaf obtained by the linear light source measuring device are relatively accurate,and the apparent texture of the blade can be reproduced well. |
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