by James Mulholland @ 9:38 am 21 February 2011


Scary Tale or Fairy Tale?

A Will-o-the-Wisp in western folklore is a small glowing creature that appears at night to travelers, often near swamps or marshes. In these stories, this sprite lures these unknowing wanderers into the deep marsh to be lost. Once the individual is far enough away from safety, the glow disappears and the person is never heard from again.

However… this will-o-the-wisp is benevolent. And fun to play with! If you’re lucky, you may just find your way out of the swamp.

Project Inspiration:
Contact Juggling – (e.g. crystal balls from Labyrinth)

openFrameworks! [code]
FireWorks and Photoshop [graphics]


  • Ball moving along skeleton
  • Flows across hands
  • Floats nicely above appendages
  • 2-player!

Further improvement:

  • position averaging (still jumpy)
  • environmental graphics (incl. background subtraction)


We used the openFrameworks with OpenNI add-on to provide the skeleton data. The ball follows the skeleton to a point lower to the ground (like gravity). Size of ball image is mapped to the depth captured by the kinect to give the illusion of depth.

Fog effect – created using difference clouds in Photoshop and displayed with alpha adjusted in openFrameworks.
Glowing Ball and Glow Effect – drawn in FireWorks with semi-transparent pixels and placed into video.

Ball image placement is offset perpendicular to the skeleton being tracked and placed relative to the outermost edge of the person (achieved through depth threshold).


Behavior tracking + movement
by Le Wei

Depth thresholding + graphics
by James Mulholland

1 Comment

  1. Great video!

    Comment by Dan Wilcox — 26 February 2011 @ 3:40 pm

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