Active Marker
Active optical systems triangulate positions by illuminating one LED at a time very quickly or multiple LEDs with software to identify them by their relative positions, somewhat akin to celestial navigation. Rather than reflecting light back that is generated externally, the markers themselves are powered to emit their own light. Since Inverse Square law provides 1/4 the power at 2 times the distance, this can increase the distances and volume for capture.
The TV series ("Stargate SG1") episodes produced using an active optical system for the VFX allowed the actor had to walk around props that would make motion capture difficult for other non-active optical systems.
ILM used active Markers in Van Helsing to allow capture of the Harpies on very large sets similar to Weta's use of active markers in "Rise of the Planet of the Apes". The power to each marker can be provided sequentially in phase with the capture system providing a unique identification of each marker for a given capture frame at a cost to the resultant frame rate. The ability to identify each marker in this manner is useful in realtime applications. The alternative method of identifying markers is to do it algorithmically requiring extra processing of the data.
Read more about this topic: Motion Capture, Optical Systems
Famous quotes containing the words active and/or marker:
“He crafted his writing and loved listening to those tiny explosions when the active brutality of verbs in revolution raced into sweet established nouns to send marching across the page a newly commissioned army of words-on-maneuvers, all decorated in loops, frets, and arrowlike flourishes.”
—Alexander Theroux (b. 1940)
“Personal change, growth, development, identity formation—these tasks that once were thought to belong to childhood and adolescence alone now are recognized as part of adult life as well. Gone is the belief that adulthood is, or ought to be, a time of internal peace and comfort, that growing pains belong only to the young; gone the belief that these are marker events—a job, a mate, a child—through which we will pass into a life of relative ease.”
—Lillian Breslow Rubin (20th century)