Motion Capture of a Red-winged Blackbird in Free Flight

Résumé du livre

We developed a motion capture system for the purpose of reconstructing the deforming wing surfaces of a bird performing sustained flapping flight. Our facility consisted of a 13-m long free flight tunnel which hosted two calibrated 500-fps digital cameras and multiple high powered lamps. The experimental setup was tested with several species. The best results were obtained with a wild, immature red-winged blackbird (Agelaius phoeniceus) whose wing joints and remiges were labeled with 3-mm retroreflective markers. For each camera's recording of the flight we digitized the 2D marker paths and from them reconstructed the 3D trajectories using the direct linear transformation method. We fit a virtual wing model consisting of bones and feathers to the marker trajectories and extracted approximate joint kinematics from the shoulder, elbow, and wrist. These time-dependent angle data of the joints compared favorably with those of the European starling (Sturnus vulgaris) obtained in wind tunnel experiments [DJJ91]. The wing model also matched the silhouettes of the red-winged blackbird when superimposed over the original footage. Although more experiments are needed to verify the accuracy of our method, future results would find diverse application in simulating the complex aerodynamics of bird flight, quantitatively comparing flight behaviors among different species for the benefit of ornithology, and animating virtual birds with heightened realism in the visual effects industry.