Real Time Visual Body Feedback & IR Tracking in

HMD Based Virtual Environments Using

Microsoft Kinects

Speaker: Srivishnu ( Kaushik ) Satyavolu

Advisor: Dr. Pete Willemsen

Thesis Problem

Analysis of using multiple kinects to implement an

inexpensive IR based tracking system, in addition to real

time 3D visual body feedback and natural interaction to the

user in HMD based Virtual Environments.

Motivation

• Absence of real time ( self ) visual body feedback in existing HMD based VEs

• Difficulties to study the perceptions / interaction of multiple users simultaneously in HMD based VEs

Full-body Tracking possible only by highly expensive tracking systems & Motion Capture suits

Initial Approach Using OpenCV

Issues???

Microsoft Xbox Kinect

Issues

• Camera Calibration

• RGB Depth Mapping

• 3D User segmentation, smoothing & representation

• IR Interference between multiple kinects

• Relative Orientation between multiple Kinects

• Tracking User Positions and/or pose

Camera Calibration & RGB Depth Mapping

Issues: Intrinsic Camera Calibration

Incorrect mapping between RGB and Depth images

Why is thisinteresting?: Accurate RGB to Depth Mapping

Solution: OpenCV Camera Calibration using Standard

Chessboard Recognition Techniques

3D User Representation

Issue: 3D Point Cloud representation

Why is this

interesting?: Real time Visual body feedback to the user

Approaches

used: Triangulation, RGB/ IR / Depth Background

Subtraction, Basic Filtering Techniques

IR Interference

Issue: Interference of IR between multiplekinects

Why is this

interesting?: For many reasons, which you will see shortly

Solution: Not as bad as expected

Unresolved at the moment

Relative Orientation between multiple kinects

Issue: Extrinsic Camera Calibration

Why is thisInteresting?: Relative Orientation of Multiple Kinects

Solutions:Manual Orientation

Automatic Calibration using OpenCV’s Chessboard Recognition Techniques

Others?

User TrackingIssues: Tracking User Position, Orientation & Pose

across large VR Lab spaces

Why is it Interesting?: Real time 3D Natural Interaction by User

across VR Lab spaces

Solution: IR Based Kinect Tracking System?

IR based Kinect Tracking System

• What is it for?– Track User Head Position and orientation ( possibly ) in VR Lab

Spaces

• How is it done?– Tracking an IR marker across a VR Space ( how large??? )

• Why do we need it?– Interference issues ( again?? ) with existing Tracking Sytems like

World Viz etc.– Extending OpenNI and Microsoft SDK pose estimation

techniques( effects of interference?? )

Issues

• External Interference ( and again??? )

• Marker visibility

• Jitter / Noise

Current Approach

• Principle of locality

• Multiple Kinects ( interference??? ) over the network

• Mean Filter

• Interpolation???

Experiments & Results

Experiment #1: Evaluation of noise/jitter of kinect's

IR based position tracking over a large space

Results:

Standard Deviation: 0.001 – 0.003 % of the mean

Future Scope & Conclusion• Photorealisitc and real time 3D Self Representation

– 3D Visual Body Feedback to the User

• Real time 3D Natural Interaction of the User across VR lab spaces– Kinect Based IR tracking System in conjunction with

Microsoft / OpenNI pose estimation techniques

• Increased perception and level of presence in VEs– Yet to be verified, but it's quite possible

• Better understanding of HMD based VEs with multiple users

References

• Libfreenect

• Nicholas Burrus’ work ( RGBDemov0.4)

• Oliver Kreylos’ Kinect Viewer

• OpenCV

• And all the other websites from which I downloaded some of the images used in this presentation

THANK YOU

Questions?