These are photos taken from our IHPC visit, featuring the CAVE enviromment and VR equipment. The VRML representation of the Oil Refinery model was simulated over the system as can be seen in the figures. The result was a stunning 3-D manifestation of our combined efforts of brainstorming, conceptualization, CAD modeling and VRML transposition.

Please click on the image to enlarge.

An introduction to CAVE 

The CAVE (CAVE Automatic Virtual Environment) is a projection-based VR system that surrounds the viewer with 4 screens. The screens are arranged in a cube made up of three rear-projection screens for walls and a down-projection screen for the floor; that is, a projector overhead points to a mirror, which reflects the images onto the floor. A viewer wears stereo shutter glasses and a six-degrees-of-freedom head-tracking device. As the viewer moves inside the CAVE, the correct stereoscopic perspective projections are calculated for each wall. A second sensor and buttons in a wand held by the viewer provide interaction with the virtual environment.

The current implementation of the CAVE uses three walls and the floor. An SGI Onyx with two Infinite Reality graphics pipelines, each split into two channels controls the projected images. For testing, you can run the CAVE using any number of walls simultaneously. The number of CAVE walls used does not change your program. The CAVE library determines which walls you want to use and does the necessary setup when your program starts.

A diagram of the CAVE environment is shown below:

CAVE Equipment

Under normal operation, CAVE users should only be concerned with turning on and off the different components. However, due to ongoing CAVE research, the hardware configuration could change occasionally. The following is a description of the CAVE equipment.

Ø      Projectors and mirrors

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. The projectors are very sensitive to almost everything. It takes at least one hour to align and calibrate each projector and mirror to match at the corners of the CAVE.

Ø      Stereo glasses

To see the virtual environment in stereoscopic 3D, users wear Stereographics' CrystalEyes liquid crystal shutter glasses. The glasses are very fragile. Pressing a small button located on the right side of the frame will turn on the glasses. To turn them off, press the same button. They will not work if the user is facing away from the emitters.

Ø      Stereo emitters

The stereo emitters are little white boxes placed around the edges of the CAVE. They are the devices that synchronize the stereo glasses to the screen update rate of 120Hz or 96Hz. They are always on.

Ø      Wand

A wand (a 3D mouse) with buttons is the interactive input device. Currently, EVL has two wands; both wands use the Ascension Flock of Birds tracking system, but have different control devices. The primary wand has three buttons and a pressure-sensitive joystick. It is connected to the CAVE through a PC, which is attached to one of the Onyx's serial ports. A server program on the PC reads data from the buttons and joystick and passes them to the Onyx. The older wand just has three buttons, and is attached to the mouse port of the Onyx. When using the older wand, be sure that the mouse pointer is on the main screen (the ":0.0" display) while the CAVE is running, or your program will not be able to detect the state of the wand buttons.

Ø      Tracking systems

The CAVE supports several different tracking systems. The primary system is an Ascension Technologies Flock of Birds. Alternative systems include the Ascension Spacepad and the Logitech sonic tracker. There are also "simulated" tracking options available, using either the keyboard and mouse or a spaceball. The use of one or another is transparent to the CAVE programmer, since it is defined in the CAVE configuration file. Systems typically have two sensors, one for tracking the user's head, and another for the wand.

Ø      Audio system

The audio system components are: an Indy workstation, speakers, a MIDI interface, and synthesizer.

The Indy functions as a "sound server" for the CAVE. Commands are sent to the workstation over the network, and it then either generates sounds internally, or controls the synthesizer.

The speakers are located in the corners of the CAVE. They are always turned on. Everything is controlled from the synthesizer.

The MIDI interface and synthesizer are located on a rack next to the CAVE.

Ø      Workstation

The current implementation of the CAVE runs using a Silicon Graphics Onyx with three Reality Engine 2s. Each Reality Engine is attached to a CAVE wall.

ImmersaDesk

The ImmersaDesk is a drafting-table format virtual prototyping device. The ImmersaDesk features a 4x5-foot rear-projected screen at a 45-degree angle. The size and position of the screen give a wide-angle view and the ability to look down as well as forward.

A diagram of the Immersadesk is shown below: