In one research and development project aimed at the training of firefighters, the traditional helmet-mounted display of visual and auditory stimuli is being extended to include the display of odor and radiant heat stimuli (Cater et al., 1994). The current version of this experimental system, which makes use of a 44 lb backpack for housing the special additional equipment required, includes both a computer-controlled odor delivery system and a computer-controlled radiant heat delivery system. The odor system delivers odors by blowing air across microcapsules crushed by pinch rollers; the radiant heat system provides directional as well as overall intensity characteristics by controlling the individual intensity of infrared lamps arranged in a circular array.

The visual display component of the system is driven by video outputs of two Silicon Graphics Indigos (one for each eye); Polhemus Fastrak position information is processed by a PC and communicated to one of the Indigos via an RS-232 serial bus; another Indigo serial bus controls the odor delivery subsystem; a third serial connection on the second Indigo drives a MIDI bus to control the radiant heat subsystem; and an Ethernet connection between the two Indigos is used for synchronization purposes and for sharing peripheral information.

The demonstration program Pyro makes use of two virtual human arms and hands, Polhemus trackers attached to the user's wrists, a virtual torch, and some virtual flammable spheres. The user's task in this demonstration is to light each of the spheres with the torch.

Among the problems encountered in this work are the visualization of the flame, gumming up of the pinch rollers used to crush the odor microcapsules, and the weight of the backpack.

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