Capturing the 3D Capturing the 3D motion of ski jumpersmotion of ski jumpers

Capturing the 3D Capturing the 3D motion of ski jumpersmotion of ski jumpers

Trip to Bonn (13-16 Nov 2005)Trip to Bonn (13-16 Nov 2005)

Atle NesAtle Nes

Faculty of Informatics and e-LearningTrondheim University College

Project description- Goal: Design a multiple video

camera system that can be used to capture and study the motion of ski jumpers in 3D.

- Task: Want to give feedback to the Task: Want to give feedback to the ski jumpers that can help them to ski jumpers that can help them to improve their jumping skills.improve their jumping skills.

How?• Multiple video cameras placed in a

ski jumping hill are used to capture image sequences of a ski jump from different angles synchronously.

Image Acquisition(capture video of

ski jumper)

Video Images

Image Processing(detect, identify &

track points)

2D ImageCoordinates

Photogrammetry(2d 3d mapping) 3D Object

Coordinates

Motion analysis (select & interpret

motion data)

Vizualization(relate 3d points to

ski jump model)

Camera equipment3x AVT Marlin cameras:• IEEE-1394 FireWire DCAM • Resolution 640x480 x 30 fps x

8 bit grayscale • 3x 9 MB/s = 27 MB/s• Changeable lenses

Camera equipment (cont.)

Operating long distances: • 3x 400 m optical fibre extension for

firewire (signals and data)• 3x 25 m power cables• 600 m synchronization cablePC: 2.4 GHz Intel P4, 4x Firewire buses,

2GB RAM (buffered), 2x WD Raptor 10.000 rpm in RAID-0 (harddisk)

Camera setup

Video data + Control signals

Synch pulse

Video processing• Points are automatically detected, Points are automatically detected,

identified and tracked over time identified and tracked over time and accross different views.and accross different views.

• Reflective markers are placed on the ski jumpers suit, helmet and skies.

Photogrammetry• Matching corresponding feature Matching corresponding feature

points from two or more cameras points from two or more cameras allows us to calculate the exact allows us to calculate the exact position of that feature point in 3D.position of that feature point in 3D.

• Assumes that one knows the Assumes that one knows the position and viewing direction of position and viewing direction of each camera.each camera.

Camera calibration• Measure exact coordinates in the

hill using differential GPS and land survey robot station.

• Place visible markers at those spots and estimate a geometry (relationship between 2D and 3D).

• Reconstruction is then trivial.

Visualization• Feature points are connected back

onto a 3D model of the ski jumper.• Allowed to be moved

and controlled in a large static model of the ski jump arena.

Granåsen ski jump arena

Conclusion• A lot of challenging topics• Remains to be seen how well the

ski jumpers will perform based on this kind of feedback.

Are you ready to jump?