An ethological motion capture system

The motion of living beings can be recorded with motion capture systems. The recorded data can be used to animate virtual characters. There are many methods used by motion capture systems. The paper presents the development of a motion capture system for more than one performer with active optical markers. The performers wear homogenous, illuminating markers attached to each relevant joint. Movements are captured by 6 high speed cameras in order to determine the markers´ position in the cameras´ image. The cameras operate at 60 fps. The image processing is distributed among multiple computers. Luckily most of the image processing tasks are highly parallel, so the high parallel computational capacity of modern programmable GPUs can be exploited. The main computer calculates the markers´ 3D positions after it receives the 2D data from image processing. Each marker needs to be identified, so the markers´ 2D and 3D positions are tracked. A hierarchy can be defined between the points in the point cloud, which can be used to determine the bones´ hierarchical transformation chain in the characters´ skeleton. To achieve satisfying results precise calibration is required.