View Full Version : Re: State of the Art in Markerless Motion Tracking

03-19-2008, 09:37 AM
This is Alex Czarowicz, VP at Organic Motion - posting the official
Organic Motion response to questions and statements about our computer
vision / markerless 3D motion tracking technology.
First we want to thank all of you who have taken the time to post your
comments. Some of these posts did include a few inaccuracies about our
technology, and we wanted to join the discussion and 'set the record

Below we outline how BioStageTM - Organic Motion's solution for the Life
Sciences works from a technical perspective, and address the validation
process and other ongoing developments.

An Overview of BioStage - how it works:

BioStage breaks away from the pattern comparison approach used by all
optical marker-based systems. Instead BioStage actually 'sees' the
entire person and tracks thousands of points on each subject. BioStage
recognizes human shapes and can analyze precise activity without any
need for attached 'cheating' devices (markers). We do not have a
library of movements that helps build our tracking model; instead
BioStage tracks a person's actual full body motion in real-time.

BioStage uses 14 monochrome 2D cameras to view the subject and
incorporates three general processes to create an accurate 3D model of
the subject in real-time:

Video Sub-System
The Video Sub-System acquires lens and space calibrated video from the
cameras and delivers these synchronized streams to the reconstruction

3D Reconstruction System
The 3D Reconstruction System turns the 2D video streams into 3D point
and surface clouds by triangulating the various 2D viewpoints. In this
way the 3D Reconstruction System acts much like a 3D scanner. This
system generates massive amounts of data that resembles the human
subjects as they appear inside the scan space.

Character Fitting System
The last step involves "recognizing" the human figure in this 3D data
cloud. Here BioStage uses a complex rules based approach which maps a 3D
humanoid skeleton into the data. The output data BioStage delivers is
the X, Y and Z positions and orientation (6 DOF) of 21 segments of this
skeleton and is then loaded in real-time through a plug-in directly into
biomechanical processing software (The MotionMonitor from Innovative
Sports Training or Visual3D from C-Motion). In addition a full 3D mesh
image, complete with surface textures is provided.
Currently the Character Fitting System is specialized to recognize and
track a typical human biped.

The capture volume can range from about 4 by 4 feet, up to approx 16 by
16 feet, and is flexible in its way to be set up for different analysis
needs/tasks in a lab. The current version of BioStage includes a
reflective white cloth backdrop which makes it easier for BioStage to
process the video data. A color camera system will make BioStage more
flexible to scan subjects without the need for the reflective backdrop.
Organic Motion will implement the color camera system within the year.

Data formats:
BioStage generates data that flows real-time into both The MotionMonitor
from Innovative Sports Technology and Visual 3D from C-Motion. Organic
Motion also provides an SDK to access the motion data directly.

Ongoing Development & Validation:

Organic Motion is in the process of performing validations of BioStage
for the Life Science community, with the expectation to demonstrate its
tracking accuracy. We are currently involved in several validation
projects, and are seeking one or two more validation studies at this

The requirements/goals of these studies are to:
a. provide a fitting system that ensures precise, repeatable, consistent
length measurements of human bones/segments.

b. deliver anthropometric measurements through a defined protocol in a
totally "non-invasive" method in real-time.

c. evaluate BioStage, its performance, and to assess its accuracy,
reliability and suitability for use in research, sports and clinical

d. perform an assessment of errors that affect temporal, kinematic, and
kinetic variables when estimated by means of the proposed markerless
system compared to the existing markerbased motion capture systems using
reflective markers currently used in motion analysis.

e. validate BioStage for biomechanical research, sports and clinical
I will be glad to show some of the research done so far on an individual
basis with typical confidentiality rights in place.

For further questions/comments please contact me at
Thank you.

Alex Czarowicz