Advanced Building Simulation

quality CRT screens, wide field of view optics, superior tracking and reduced intrusiveness
makes this device suitable for many applications where precision is needed.
The CAVE on the other hand, is a projection-based totally immersed environment that
surrounds the viewer with four screens. The screens are arranged in a cube made up of
three projection screens for walls and a projection screen for the floor (Figure 9.16). The
projectors and the mirrors for the sidewalls are located behind each wall. The projector
for the floor is suspended from the ceiling of the CAVE, which points to a mirror that
reflects the images onto the floor. A viewer wears Stereographics’ CrystalEyes liquid
crystal stereo shutter glasses and a 6-DOF head-tracking device (the CAVE supports several
types of tracking systems). As the viewer moves inside the CAVE, the correct stereoscopic
perspective projections are calculated for each wall. The stereo emitters are placed
around the edges of the CAVE. They are the devices that synchronize the stereo glasses
to the screen update rate of 120 or 96Hz. A wand (a 3D mouse) with buttons is the
interactive input device. The primary wand has three buttons and a pressure-sensitive
joystick. It is connected to the CAVE through a PC, which is attached to the supercomputer
serial ports. A server program on the PC reads data from the buttons and joystick
and passes them to the supercomputer.
The standard CAVE is a ten-foot cube. The origin of the coordinate system (0, 0, 0)
for the CAVE is normally located at the center of the floor, that is five feet away from
any wall. This means that the programmer has from �5 to �5 feet horizontally and
from 0 to 10 feet vertically to define objects inside the CAVE. All the walls of the
CAVE share the same reference coordinate system.
VIEW AND THE VIEWER
Simulation
& graphics
Figure 9.16 A diagram of the CAVE environment.
Immersive building simulation 231
CAVE environment
Due to eye anatomy, each user in the immersive environment can perceive the view
slightly differently. The viewing parameters contribute an important component to
the registration problem (Figures 9.17 and 9.18). These parameters include: the center
of projection and viewport dimensions, offset between the location of the head
tracker and the viewer’s eyes and field of view (FOV).
Transformation matrices are used to represent the view registration. These matrices
need to be aligned with the tracker system employed. For example, a magnetic