Motion Capture Laboratory

Motion CaptureLaboratoryViktor Devecseri

Introduction• Sampling the pose and location of a subject over time.

• Optical motion capture

Markers

Multiple cameras

3D position reconstruction ofmarkers

Rigid body orskeleton information

3D Reconstruction

u2

v2w2

u1

v1

w1

[X,Y,Z]

P1

P2

t1

t2

Camera frustum

Camera frustum

Camera frustum

Camera placementoptimization

System overview

Marker extraction

Reconstruction

User Interface

Calibration

Marker extraction – Cameras

Markers Cameras Pixels Image processingMarker

positions

• Web cameras

640x480 @ 30 FPS

• PlayStation 3 Eye

640x480 @ 60FPS

• uEye cameras

Industrial camera

1024x768 @ 30FPS

• Basler cameras

Industrial camera

658x492 @ 120 FPS

• On the GPU

CUDA

1-2 ms processing

• Realtime processingat 120 FPS

Marker extraction –Distributed

Image

Processing

Image

Processing

Image

Processing

3D reconstruction

Marker extraction –OptiTrack

Markers 18 x OptiTrack Flex 13Marker

positions

• 1280x1024 @ 120 FPS

• IR Leds, passive markers

• On-camera image processing

Reconstruction• Point correspondence

Matching points on different camera views

Epi-polar geometry

• Marker position reconstruction

• Model fitting

Rigid body

Skeleton

Calibration• Camera parameters

Intrinsic parameters (focal length, principal point, distortion)

Extrinsic parameters (position, orientation)

• Two steps

Starting estimation for each camera

Built-in methods in OpenCV for both intrinsic and extrinsic

Bundle adjustment for whole camera system

Wanding

Levenberg-Marquard algorithm

• Average error: 0.233cm

Rigid body

n

i

ii qdRp1

2min

Reference points Current points

Skeleton

User interface

Future work• Automatic marker labeling for skeleton

• Robust handling of missing and reappearing markers

• Skeleton calibrationshoulder

elbow

wrist

Conclusions• Different types of cameras

GPU based real-time image processing at 120 FPS

Scalable

OptiTrack cameras

• Modular design, easy extension

• Good calibration <0.5 cm accuracy

• Improving skeleton tracking

Thank you!Questions?

EEA Financial

Mechanism 2009-2014 -

HU08 Scholarship

Program

BUTE, Department of

Mechatronics, Optics and

Mechanical Engineering

Informatics

Narvik University College

Energy Agency Public

Nonprofit Ltd.

COLLECTIVE DEVELOPMENT OF MODERN EDUCATIONAL METHODOLOGIES IN THE

FIELD OF ONLINE MEASUREMENT, -CONTROL AND REMOTE MONITORING SYSTEMS