Christopher Koehler

3D reconstruction and analysis of wing deformation in free-flying dragonflies

SUMMARY Insect wings demonstrate elaborate three-dimensional deformations and kinematics. These deformations are key to understanding many aspects of insect flight including aerodynamics, structural dynamics and control. In this paper, we propose a template-based subdivision surface reconstruction method that is capable of reconstructing the wing deformations and kinematics of free-flying insects based on the output of a high-speed camera system. The reconstruction method makes no rigid wing assumptions and allows for an arbitrary arrangement of marker points on the interior and edges of each wing. The resulting wing surfaces are projected back into image space and compared with expert segmentations to validate reconstruction accuracy. A least squares plane is then proposed as a universal reference to aid in making repeatable measurements of the reconstructed wing deformations. Using an Eastern pondhawk (Erythimus simplicicollis) dragonfly for demonstration, we quantify and visualize the wing twist and camber in both the chord-wise and span-wise directions, and discuss the implications of the results. In particular, a detailed analysis of the subtle deformation in the dragonflys right hindwing suggests that the muscles near the wing root could be used to induce chord-wise camber in the portion of the wing nearest the specimens body. We conclude by proposing a novel technique for modeling wing corrugation in the reconstructed flapping wings. In this method, displacement mapping is used to combine wing surface details measured from static wings with the reconstructed flapping wings, while not requiring any additional information be tracked in the high speed camera output.

Vortex Visualization in Ultra Low Reynolds Number Insect Flight

We present the visual analysis of a biologically inspired CFD simulation of the deformable flapping wings of a dragonfly as it takes off and begins to maneuver, using vortex detection and integration-based flow lines. The additional seed placement and perceptual challenges introduced by having multiple dynamically deforming objects in the highly unsteady 3D flow domain are addressed. A brief overview of the high speed photogrammetry setup used to capture the dragonfly takeoff, parametric surfaces used for wing reconstruction, CFD solver and underlying flapping flight theory is presented to clarify the importance of several unsteady flight mechanisms, such as the leading edge vortex, that are captured visually. A novel interactive seed placement method is used to simplify the generation of seed curves that stay in the vicinity of relevant flow phenomena as they move with the flapping wings. This method allows a user to define and evaluate the quality of a seeds trajectory over time while working with a single time step. The seed curves are then used to place particles, streamlines and generalized streak lines. The novel concept of flowing seeds is also introduced in order to add visual context about the instantaneous vector fields surrounding smoothly animate streak lines. Tests show this method to be particularly effective at visually capturing vortices that move quickly or that exist for a very brief period of time. In addition, an automatic camera animation method is used to address occlusion issues caused when animating the immersed wing boundaries alongside many geometric flow lines. Each visualization method is presented at multiple time steps during the up-stroke and down-stroke to highlight the formation, attachment and shedding of the leading edge vortices in pairs of wings. Also, the visualizations show evidence of wake capture at stroke reversal which suggests the existence of previously unknown unsteady lift generation mechanisms that are unique to quad wing insects.

An Integrated Analysis of a Dragonfly in Free Flight

There were few literatures on the discussion of the wing flexion and associated aerodynamic performance of dragonfly wings in dragonfly free flights, which are potential candidates for developing bio-inspired micro aerial vehicles (MAVs) that can match the hovering and maneuvering performance of winged insects. To this end, we experimentally measure the wing flexion of a free flying dragonfly during take-off using high-speed photogrammetry and three-dimensional surface reconstructions. From the collected data, analysis of body motion Euler angles, SVD analysis of wing kinematics, wing surface deformation and topologies, and direct numerical simulations will provide insights into the selection of flapping wing and kinematics for quad-winged MAV designs and applications.

Knowledge-Assisted Reconstruction of the Human Rib Cage and Lungs

Computer-aided disease detection software effectively helps medical professionals use PA (posterior-anterior) and lateral (side) x-ray images to detect diseases such as lung cancer at early stages, which can be quite difficult. Typically, such software focuses only on PA x-ray images and uses image-processing and soft-computation techniques to identify potentially diseased areas. Theres been little focus on extracting knowledge from the x-rays and using knowledge of human anatomy to generate 3D reconstructions. Such reconstructions could help the detection process by providing a different way of visualizing the x-ray data to better investigate hard-to-diagnose regions.

Reconstructing the human ribcage in 3d with x-rays and geometric models

To avoid lung disease, regular preemptive screenings are an absolute necessity. This article describes a technique that creates a 3D reconstruction of the ribcage without expensive scanners. One of the major uses of this 3D reconstruction software would be as a medical visualization tool that would show the real shape of a ribcage. This 3D reconstruction method could be combined with diagnosis software to help detect lung cancer, to generate 3D size estimates, and to improve visualization of affected regions.

3D Reconstruction of Human Ribcage and Lungs and Improved Visualization of Lung X-Ray Images through Removal of the Ribcage

The analysis of X-ray imagery is the standard pre-screening approach for lung cancer. Unlike CTscans, X-ray images only provide a 2D projection of the patient’s body. As a result occlusions, i.e. some body parts covering other areas of the body within this projected X-ray image, can make the analysis more dicult. For example, the ribs, a predominant feature within the X-ray image, can cover up cancerous nodules, making it dicult for the Computer Aided Diagnostic (CAD) systems or even a doctor to detect such nodules. Hence, this paper describes a methodology for reconstructing a patient-specific 3D model of the ribs and lungs based on a set of lateral and PA X-ray images, which allows the system to calculate simulated X-ray images of just the ribs. The simulated X-ray images can then be subtracted from the original PA X-ray image resulting in an image where most of the cross hatching pattern caused by the ribs is removed to improve on automated diagnostic processes.

Knowledge-Based 3D Reconstruction and Visualization of Human Ribcage and Lungs

To help mimic some of the useful features of CT scans for early detection of diseases like lung cancer at a fraction of the cost, a knowledge‐assisted interactive 3D ribcage and lung reconstruction algorithm is proposed. The ribcage and lung reconstructions are both based on the typical PA (rear) and Lateral (side) X‐ray images that are already being acquired during preemptive screenings for lung cancer. Shared domain knowledge of human anatomy and solid modeling techniques are combined with knowledge automatically extracted from the X‐ray images through computer vision algorithms to transform a series of primitive template meshes into reconstructed ribs and lungs despite the fact that much of the 3D information is lost during the X‐ray process. An example of how the reconstructed lung geometry can be used to clip the portion of an approximate volume reconstruction to provide a supplementary interface to search for potential diseased areas is presented.