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Experimental method for 3D reconstruction of Odonata wings (methodology and dataset)

Citation

Chitsaz, Nasim; Marian, Romeo; Chahl, Javaan (2020), Experimental method for 3D reconstruction of Odonata wings (methodology and dataset), Dryad, Dataset, https://doi.org/10.5061/dryad.6t1g1jwtt

Abstract

Insect wings are highly evolved structures with aerodynamic and structural properties that are not fully understood or systematically modeled. Most species in the insect order Odonata have permanently deployed high aspect ratio wings. Odonata have been documented to exhibit extraordinary flight performance and a wide range of interesting flight behaviors that rely on agility and efficiency. The characteristic three-dimensional corrugated structures of these wings have been observed and modeled for a small number of species, with studies showing that corrugations can provide significant aerodynamic and structural advantages. Comprehensive museum collections are the most practical source of Odonata wing, despite the risk of adverse effects caused by dehydration and preservation of specimens. Museum specimens are not to be handled or damaged and are best left undisturbed in their display enclosures.  We have undertaken a systematic process of scanning, modeling, and post-processing the wings of over 80 Odonata species using a novel and accurate method and apparatus we developed for this purpose. The method allows the samples to stay inside their glass cases if necessary and is non-destructive. The measurements taken have been validated against micro-computed tomography scanning and against similar-sized objects with measured dimensions. The resulting publicly available dataset will allow aeronautical analysis of Odonata aerodynamics and structures, the study of the evolution of functional structures, and research into insect ecology. The technique is useable for other orders of insects and other fragile samples.Insect wings are highly evolved structures with aerodynamic and structural properties that are not fully understood or systematically modeled. Most species in the insect order Odonata have permanently deployed high aspect ratio wings. Odonata have been documented to exhibit extraordinary flight performance and a wide range of interesting flight behaviors that rely on agility and efficiency. The characteristic three-dimensional corrugated structures of these wings have been observed and modeled for a small number of species, with studies showing that corrugations can provide significant aerodynamic and structural advantages. Comprehensive museum collections are the most practical source of Odonata wing, despite the risk of adverse effects caused by dehydration and preservation of specimens. Museum specimens are not to be handled or damaged and are best left undisturbed in their display enclosures.  We have undertaken a systematic process of scanning, modeling, and post-processing the wings of over 80 Odonata species using a novel and accurate method and apparatus we developed for this purpose. The method allows the samples to stay inside their glass cases if necessary and is non-destructive. The measurements taken have been validated against micro-computed tomography scanning and against similar-sized objects with measured dimensions. The resulting publicly available dataset will allow aeronautical analysis of Odonata aerodynamics and structures, the study of the evolution of functional structures, and research into insect ecology. The technique is useable for other orders of insects and other fragile samples.

Methods

Wing parameters were measured for 80 individuals of eight different families of Odonata in the collection located in the South Australian (SA) museum through the non-destructive photogrammetry method. In this study, the corrugated wing geometry of dragonflies for both forewing (FW) and hindwing (HW) were exported, which both play significant roles in the aerodynamic performance of dragonflies. The main priority in this research was the preserve of Odonata according to the museum regulation and standards to access as many samples as possible. With this in mind, an attempt was made to develop a method that does not disturb the samples by any means. Handling was restricted to only opening the sliding drawers and viewing from behind the glass, not removing or directly handling the dragonflies at all. The photos taken were then “stitched” together using software to form a 3D image. With this technique, all of the texture, detail and color of the wing are clear.

The resultant sequence of photographs (approx. 100 images per wing) was used to create a 3D model of the Odonata, and depending on the size would take up to 10 minutes per wing to compute a solid model. The procedure was carried out on a high-performance desktop PC with an Intel Corei7 CPU 3.60 GHz, installed memory 64.0 GB and also GPU (GeForce GTX 1080 Ti) necessary for making a 3D model of the wing with the 3DF Zephyr software. A total of 100 individual dragonflies of two main suborders, Zygoptera and Epiprocta, from the collection were photographed.  The specimen had been stored in the wooden boxes which were covered by glass and were fitted with a white mat.  From each insect, nearly 100 high-resolution photographs of 4016 × 6016 pixel resolution from a sequence of positions were taken. Every photograph had the same background, and the specimen was undisturbed.  To obtain an accurate result, as a minimum requirement, the Zephyr software requires that each part of the object that was photographed appeared in at least three separate views taken from different locations. Another determining parameter for obtaining a reliable result was to limit the angles between photos. Care was therefore taken to keep the angles between each photograph small.