A good novel is immersive without any fancy graphics or audio hardware. You 'see' and 'hear' and 'touch' and 'taste' and 'smell' A good play or a film or an opera can be immersive using only sight and sound. But they aren't interactive which is another key element. Another key element of VR is a viewer centered perspective where you 'see' through your own eyes as you move through a computer generated space, interact with objects there, and more often than not kill everyone you meet. The way you see the environment is limited to a screen with a narrow angle of view and you use a keyboard / joystick / gamepad to change your view of that scene.
the visual (and aural and haptic) displays that immerse the user in the virtual world and that block out contradictory sensory impressions from the real world; the graphics rendering system that generates, at 20 to 30 frames per second, the ever-changing images; the tracking system that continually reports the position and orientation of the user’s head and limbs; and the database construction and maintenance system for building and maintaining detailed and realistic models of the virtual world.
The walls of the CAVE are made up of rear-projection screens, and the floor is made of a down-projection screen. High-resolution projectors display images on each of the screens by projecting the images onto mirrors which reflect the images onto the projection screens. The user will go inside of the CAVE wearing special glasses to allow for the 3-D graphics that are generated by the CAVE to be seen. With these glasses, people using the CAVE can actually see objects floating in the air, and can walk around them, getting a proper view of what the object would look like when they walk around it. This is made possible with electromagnetic sensors.