WestMotion
Realistic
character animation is a permanent challenge
faced by computer artists. In this field,
motion capture techniques allowed significant
advances. These technologies make it possible
to recreate movements of a real actor on
a virtual creature.
The
very high pricing of professional solutions
led Westimages to study the feasibility
of a low cost Motion Capture system. Amongst
existing methods, we chose optical capture
for its scalability. It is based on the
use of markers attached to joints of the
body. The coordinates of the markers are
used to animate the virtual model.
The
application developed by Westimages relies
solely on 2 standard DV cameras. Before
each Motion Capture session, each camera
must be calibrated. Analyzing the correspondences
between reference points with known 3D coordinates
and their 2D images, the software « learns »
how each camera projects the scene. The
next step consists in labelling and tracking
the markers in each video sequence. Finally,
the correspondences between the two views
are established, thus allowing for a 3D
reconstruction using a triangulation method.
The software has been successfully tested
in a real situation, during which the motion
of a human hand was captured. This study
proved the feasibility of a low cost Motion
Capture tool, featuring a reduced equipment
price.
Certain
issues have still to be adressed so as to
provide a complete solution. In particular,
occlusion management needs to be implemented.
Occlusion occurs when an object gets in
the way between the camera and the marker,
thus making the maker invisible for a limited
amount of time. To solve this problem, an
increase in the number of cameras is considered
along with the use of predictive algorithms.
Besides, the 2D tracking engine still requires
manual pre-processing of video sequences.
An enhanced engine using feature recognition
techniques would suppress this pre-processing
step. At last, a Human Machine Interface
is needed to bring the software to a sufficient
usability level.
WestMotion
in the future...
In
the long run, Westimages plans to develop
a real time Motion Capture tool. Current
research publications demonstrate the feasibility
of such a system, in which each video stream
is processed by a dedicated unit. A central
processor uses the 2D information extracted
from each view to produce a 3D reconstruction.
The arrival of multi core configurations
in PCs leads to serious consideration of
those architectures.
|
