Tuesday, June 19, 2012

Motion capture part 1

In 2003 at the University of Illinois at Urbana-Champaign we presented the first ever use of an infrared motion capture system for live interactions on stage.  The resultant work was "Bob's Palace."  While it was a first in 2003 it would still be a feat to make this happen today.  Sophisticated motion capture systems used by scientists are very precise and require stable lab environments free from infrared light (and heat emiting light...) in order to function properly.  Most lights pre-installed in theaters today emit infrared light :)  In 2003 we were always looking to put enough light on the dancers so they could be seen and not completely crash the system.

Nic Petry dancing with markers on his untitard with 25 infrared cameras around his body with an avatar above him...

2003 cast of Bob's Palace performing in an excerpt

In Somatophobia I am using a very different system to capture motion.  The system made by Worldviz is made to explore gaming 3D environments.  It allows us to capture a "point" in space and with the help of another system what direction this point is facing.  It's much simpler than the 40 reflective balls we had to wear on our bodies in 2003.

The advantage of using a 3D motion sensing system is that all directions in space can affect the animation.  This is difficult to understand unless you have moved in one of these environments in the past. 
  1. A 1D system is like your basic burglar motion sensing switch in your room.  The system doesn't really know where you are... it just knows you are moving in the room.  If you stop moving or are moving below the threshold the system doesn't know you are there.  
  2. A 2D capture system can usually tell where you are along a sensing strip.  A piano is a 2D system.  When your hand moves up the scale we can "hear" where you are :)  Most people don't use pianos as motion capture systems but they could... you can imagine a room rigged to make a sound depending on where you are in the room.  Now whether you jump or roll will not make a difference here.  It might create a rhythm if you are jumping (and the sensors are on the floor...) but the system won't care if you are a duet or a single person jumping on one leg.  In these systems it is usually hard to distinguish a body part from another.  Some do it with colors where a camera can "see" a red glove and follows the glove and compares it to a vertical 2D grid pre-established by the designer.
  3. A 3D system would allow us to make many more distinctions.  Usually we can differentiate between the head and a foot and we can start to see how these body parts are relating to each other.  
Why would we go through such trouble just to capture motion?  interacting with our bodies in sophisticated 3D systems develops an awareness of space.  It allows us to "feel" space from a different perspective and this can allow us to connect and integrate the information into a better functioning body. 

Pictures and video to follow soon...

1 comment: