Modelling Method Of Wheat Plant Based On 3D Digitization And Mesh Deformation

The three-dimensional(3D)morphological structure of wheat directly represents the interaction between genetic characteristics,environment and cultivation measures.However,due to the large number of leaves in the plant canopy and the diversity of spatial posture of leaves,it has always been a challenging research topic to achieve the rapid and accurate extraction of phenotypic parameters and 3D modelling of wheat morphological structure.Taking winter wheat as an example,this paper focuses on the precise extraction of wheat morphological structure phenotypic parameters and the 3D modelling method of highlighting detailed morphological features,and then virtual interactive application was combined with Virtual Reality(VR).This study provides technical solutions for 3D modelling of wheat morphological structure,3D phenotypic characteristics analysis,wheat structure and function analysis based on 3D visualization model and so on.The main contents and results are as follows:(1)A method for extracting wheat morphological structure phenotypic characteristic parameters based on 3D digitization was proposed.Firstly,a 3D digital data acquisition specification suitable for the whole growth period of wheat was formulated.According to this standard,quantitative extraction methods for eleven conventional phenotypic parameters in three categories,including lengths,thicknesses,and angles of wheat plants and organs were realized.Furthermore,the parameter circum for quantifying the degree of looseness or compactness of wheat plants were put forward,and five leaf morphological feature parameters including Leaf size ratio,Max-leaf width position,Leaf sag,Leaf bending,and Leaf twisting were used to describe the 3D spatial posture of wheat leaves.Results showed that the proposed method can achieve convenient and accurate extraction of wheat phenotypes.Without destroying the morphological structure of wheat plants,the errors of leaf length,leaf width,stem length,stem thickness,stem and leaf angle,leaf inclination angle were small,the R~2were 0.93,0.75,0.98,0.93,0.85,and 0.73,respectively.The extracted phenotypic characteristic parameters can be used to further analyze the morphological structure characteristics of wheat plants at different scales,and calculate the standard value of variety characteristics of each parameter.(2)A wheat modelling method based on mesh deformation was proposed.Taking wheat plants at the filling stage as an example,a leaf template library containing typical leaf shape features was constructed based on 3D leaf morphological features of wheat leaves.The template samples were selected based on the similarity between the input leaf skeleton and leaf templates in the constructed wheat leaf database.And the leaf modelling was realized by using the As-rigid-as-possible(ARAP)mesh deformation method.We found that 3D wheat modelling at the individual leaf level,leaf group,and individual plant scales can be achieved.Compared with directly acquiring 3D digitizing data for 3D modelling,it saves 79.9%of the time.The minimum correlation R~2of extracted leaf morphological parameters between using the measured data and 3D model by this method was 0.91,and the maximum RMSE was 0.03,implying that this method preserves leaf morphological features.(3)A virtual interactive display system of wheat varieties was developed which is based on the difference analysis of reconstructed 3D models and extracted phenotypic characteristic parameters of different wheat varieties.It combines database knowledge,Levels of Detail(LOD)technology,Shader technology,and human-computer interaction technology.Then display and interaction through HTC-vive devices.The system realized the model display at different scales of population,single plant,and organ,so that users could experience the difference of wheat varieties through 3D interaction and immersive experience.The results show that the construction of three levels of wheat LOD can satisfy the wheat display of different scales and perspectives.Wheat virtual display systems of different varieties and scales can provide technical support for agricultural display and virtual teaching,and provide a new case for the application of VR,AR and digital twin in agriculture.