Extraction and reconstruction of a beetle forewing cross-section point set and its curvature characteristics

To develop lightweight and high-strength curved beetle elytron plates (CBEPs), an algorithm to extract a cross-section point set based on three-dimensional point cloud data measured from a beetle forewing and to reconstruct its outer surface was designed. This approach was used to study three beetle species. The curve fitting method and the curvature distribution characteristics of the corresponding forewings during the reconstruction were investigated. (1) Two algorithms, namely, the median surface separation method and segmented microstrip method, were established. (2) Two types of fitting methods were proposed: judging the consistency of the curvature curve peaks to determine higher-degree polynomials (clusters) and implementing k-fold cross-validation to determine the optimal engineering fitting curve. The optimal fitting curves for the cross-section point sets of the various beetle forewings involved in this paper were discovered to be elliptic equations. (3) The curvature characteristics of the forewing cross-sections vary depending on the type of fitting curve used; accordingly, researchers can choose the most appropriate fitting curve. For the research and development of CBEPs, elliptic equations can be used to establish the required bionic structure model, the important structural parameters of which include not only the long and short axes of the ellipse but also the position and length of the segment. This paper, therefore, lays a foundation for the development of CBEPs.