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Electronic Visualization Laboratory University of Illinois at Chicago
Interaction between Real and Virtual Humans:
Playing Checkers
R. Torre, S. Balcisoy P. Fua, M. Ponder, and D. Thalmann Computer Graphics Lab (LIG)
Swiss Federal Institute of Technology
Atul Nayak
Electronic Visualization Laboratory University of Illinois at Chicago
Virtual Humans
• Guided– Represent the user
• Autonomous– Act on their own
Electronic Visualization Laboratory University of Illinois at Chicago
Virtual Worlds
Virtual humans live in synthetic worlds
Electronic Visualization Laboratory University of Illinois at Chicago
So what’s new?
• Make the virtual human interact with the user
• 2-way communication• Real-time• Non-invasive• Vision-based
recognition system
Electronic Visualization Laboratory University of Illinois at Chicago
Real time tracking of 3D objects
• To track a 3D convex object (a cube, a checkers board) we need– A camera– A target– The wire frame 3D model of the target– A powerful computer
Electronic Visualization Laboratory University of Illinois at Chicago
Model Based Tracking
• Create a mathematical model of the target• World coordinates are a function of the state
variables that control the object’s shape• An objective function is minimized to find the best
fit with image data
Electronic Visualization Laboratory University of Illinois at Chicago
3-D tracking algorithm
• Get a video image• Process the image• X(t+1) = X(t) + V(t).dT
– X = position ; V = speed ; dT = time between t and t+1
• Minimization of the objective function
Electronic Visualization Laboratory University of Illinois at Chicago
Detecting the checkers
• If the sum of the intensities of each pixel in the real image of a white square is less than a certain threshold value , it means that a piece is present on that square.
Electronic Visualization Laboratory University of Illinois at Chicago
Virtual Human Director (VHD)
• A system used to produce real-time multimedia products and TV shows
• Focuses on 2 issues– Fully integrated virtual humans with facial and
body animation, and speech– A straightforward user interface for designers
and directors
Electronic Visualization Laboratory University of Illinois at Chicago
The VHD interface
• Virtual human animation and interaction capabilities integrated into one environment
• Control multiple actors• Provide tools to create any scenery involving realistic virtual humans
Electronic Visualization Laboratory University of Illinois at Chicago
The Augmented Reality System
• Synchronize the rendering of synthetic scenes with the real camera output
• VHD animates the virtual player and updates the scene – input from tracker and checker game controller
Electronic Visualization Laboratory University of Illinois at Chicago
Image composition
• Chroma-keying : black is the key color• All real objects represented in black• Table’s virtual representation masks the virtual human• Blend the real filmed scene and the synthetic 3D scene to get
the mixed image• Real player sees the mixed image on a large monitor
Electronic Visualization Laboratory University of Illinois at Chicago
Comments
• Very realistic virtual humans will be widely used in film, games and interactive television
• Integrate VR with the Web – create 3D scenes with multimedia objects
• Replace checkers board with any other calibration object
• No extra devices – you can see yourself in the virtual world
Electronic Visualization Laboratory University of Illinois at Chicago
References
• VHD: A System for Directing Real-Time Virtual Actors, G. Sannier, S. Balcisoy, N. Magnenat-Thalmann, D. Thalmann, The Visual Computer, Springer, Vol.15, No 7/8, 1999, pp.320-329
• All images and movies in this presentation have been taken from the LIG’s website URL : http://ligwww.epfl.ch/