Information Technology Reference
In-Depth Information
2.
In order that the image is correctly projected when the fog generation point is
moved, markers were fitted to the fog generator to read its position and orientation
and adjust the projection to match those readings.
How to position the projectors when multiple users are using the system simulta-
neously, it is necessary for a given user to be able to see the images projected onto the
other users' fog screens. In order to achieve this, several projectors are arranged.
Here, taking into consideration Mie scattering, we positioned three short focus projec-
tors at approximately 60-degree intervals, at the same level and equidistant from the
center of the circle, and with their lamps aimed at the same central point. With this
arrangement, we avoid images projected from each projector overlapping due to the
directionality of scattered light, and it is possible to construct a fogscreen that can be
observed from multiple viewpoints.
2.1
Detecting the Position and Orientation of the Device
In order to detect the position and the orientation of the device, we use markers of
known shape and size and a camera with known internal parameters. If these parame-
ters are known, we can know the position and orientation of the markers [10]. Also, in
order to avoid interference with marker recognition when the images are projected
onto the markers, an infrared camera and infrared floodlight are used and the markers
are filmed in the infrared spectrum.
2.2
How to Create the Projector Output Images
In order that each projector can project an image on the fog, it is necessary to create
images adjusted according to the projection position of each projector, using the in-
formation collected in Subsection 2.2 about the position and orientation of the device.
To generate these images, we construct and use a virtual space that is geometrically
aligned with the actual space. Geometrical alignment means that the position of the
cameras set up to film the markers in the virtual space (virtual marker cameras) and
the relative positioning of the projectors (virtual projectors) are aligned with the infra-
red cameras filming the markers and the projectors in the actual space. By setting up
this alignment in advance, the detected marker positions and orientation can be direct-
ly reflected in the virtual space.
The acquired the position and the orientation of the device are reflected the device
arranged in the virtual space (virtual device) and we arrange the image we want to
project on the front of the virtual device. Furthermore, we arrange the virtual cam-
eras in the locations of each of the virtual projectors. We set the field of view of the
virtual cameras to be the same as that of the projectors. With this setup, if the virtual
cameras film the image at the front of the device, these filmed images are the images
are the images that geometrically aligned projectors must project.
