TTM4142 Networked Multimedia Systems A Robust Human-Silhouette Extraction Technique for Interactive Virtual Environments Presentation by Leif Arne Rønningen, Item, NTNU, Autumn 2008 J W Davis and A F Bobic, MIT Media Lab 1998

Sensing objects in space  Specialized light  Chorma keying  IR, UV light, other spectra  Rear light  Special surface  Special light reflectors  Lasers (triangulation)  Background subtraction  Electromagnetic field  Electric field  Acoustic field

Infrared light - IR  Extraction of frontal object silhouettes Video on back screen Infrared emitters behind back screen (diffusing) Camera with IR pass filter shoots towards back screen An object in front of the back screen blocks the IR light If the object is a user, he can see another user on a front screen IR from projectors can be easily be blocked Environment lightening need to block IR

Dual-screen Environment, Using IR light

Image of person in front of video With IR through the screen With IR filter on camera

Q Example system, Virtual PAT (see paper)

CL Discuss the quality of the IR-based silhouette xtraction scheme compared to chroma keying. What happens when the frontal object is a glass?