The mocap data are imported in Virtual Sensei software and elaborated to obtain the following outputs:
- athlete’s anthropometric parameters;
- linear and angular velocities and accelerations of each articular segment;
- translational, rotational and total kinetic energy of each articular segment and of the entire body;
- plots of the calculated characteristics;
- animation of a 3D skeleton that reproduces the athlete’s motions;
- 3D position (and projection on the ground) of the body centre of mass.
The following video shows the Graphical User Interface (G.U.I.) developed for the software Virtual Sensei:
(Music by: Free Royalty Free Music by DanoSongs.com)
The G.U.I. provides the following functions:
- navigating the scene in 3D;
- time seeking (fast, frame by frame, jump to time);
- knowing the instantaneous values of the parameters;
- detecting the 3D position and projection on the ground of the body centre of mass;
- hiding the desired limbs.
The need to observe the correspondence between performed technique and numerical data, and the purpose to understand the relation between body pose and relative energetic level, led to the implementation of a function that animates a 3D skeleton.
This reproduces the segmental subdivision of the rigid bodies adopted in the motion capture step and mimics the athlete’s movements on the computer screen. The dimensions of the skeleton can be adjusted to the athlete’s main anthropometric measurements.
The use of 3D animation instead of camcorder video allows the user to:
- obtain the animation and the result of the analysis at the same time, without the need for further steps;
- obtain a record with a frequency of 100 fps, because data moving the dummy are the same captured and exported by mocap cameras;
- play the scene from any angle and position;
- observe the details in slow-motion without seeing the typical flickering of a camcorder video;
- have a qualitative tool to check the correctness of the performed motion tracking, to immediately spot problems such as the temporary concealing of some markers;
- archive the recorded data in a disk-space of about 2-3 MB, much less than the average memory required by a traditional camcorder recording.
The visual control of motions through the 3D skeleton permits the repeatability, the correction or the elimination of a sport motion on the basis of its energetic efficiency.