is designed to be experienced live, requiring the location
and orientation of the participants head to be tracked
in real time (using some combination of electro-magnetic,
sonic, inertial, and video sensing).
If the participant wears a camera on their head (as they must do when using a video-mixed HMD), tracking information may also be gathered by attaching fiducial marks to landmarks or objects and having the computer look for this specially designed markers in the video stream. When the computer see one of these fiducials,
it can tell where the object is relative to the camera.
An AR application reacts to a participant's
location and activity moment by moment, and uses the
available tracking and sensor information to decide
what the user sees and hears. For example, if the user
is touring a university campus, the computer might draw
the names of the buildings “in the air”
together with arrows associating each name with the
Different kinds of experiences
require different kinds of content. For many experiences
that might be created with DART, the system draws three-dimensional
objects in the world around the user. DART also supports
less common forms of content, such as video-based "actors"
created by texture mapping digitized video, usually
of a human actor, onto a plane in the 3D scene.
For examples of AR experiences
created with DART, see Applications.