Biomedical Engineering Reference
In-Depth Information
Fig. 16.4
Visualizing the 2Dpixel intensity distribution of theMove's sphere is useful for debugging
the model fitting stage
the sensors all contribute to the final state in a complex manner, each has a fundamen-
tal contribution that is necessary for the complete state computation. For example,
the camera tracking provides an absolute measure of the 3D position and the
accelerometers provides the direction of gravity when the controller is not mov-
ing, which gives an absolute measure of the pitch and roll angles. In addition, when
the orientation is known, gravity can be “subtracted” from the accelerometer data to
recover the controller acceleration. The acceleration is part of the state, and it can
also be used to reduce noise in the 3D position and to derive the 3D velocity. The
gyroscope data is also crucial because it directly provides angular velocity. When
integrated, this provides a responsive measure of 3D rotation (relative orientation)
and can be used to derive angular acceleration. The remaining unknown, absolute
yaw, is the most tricky, but it can be inferred by comparing the motion direction com-
puted from body-relative inertial measurements to the motion direction computed
from camera-relative image measurements.
16.2.3 Microsoft Kinect
The Microsoft Kinect is an accessory for the XBOX 360 console that turns the user's
body into the controller. It is able to detect multiple bodies simultaneously and use
their movements and voices as input.
The hardware for the Kinect (see Fig.
16.5
) is comprised of a color camera, a depth
sensor, a multi-array microphone and a motorized tilt platform. The camera is used
to determine different features of the user and space by detecting RGB colors and is
mainly used for facial recognition of the user, an advanced feature the XBOX uses for
