The VIPE Holodeck is similar in approach to the Infantry Immersion Trainer (IIT) that was developed by Lockheed Martin to train marines, but they differ in many key ways.
IIT was designed as a mixture of mediums, including physical reconstructions that were meant to resemble Fallujah, Iraq. This scenario was complemented by a piping in of digital sounds and avatars to create a fully immersive environment.
VIPE, though, is purely digital. Aside from the individuals within the Holodeck, everything else is a projection based on simple, and inexpensive, consumer technology.