Judith Chamberlain is the webSpinner

The principles of linear perspective are required to provide depth and volume to the four-dimensional field. The VR world builder needs to be aware of overlapping planes, light, shadow and color, and relative size to provide shape and structure to an environment. If the user is going to fly, attention should be paid to aerial perspective. Objects will be affected by motion parallex--closer objects should move more than distant ones. The world builder must also go beyond visual representation issues, and deal with physical properties: What are the surfaces like? Are they smooth or rough, soft or hard? How much do objects weigh? What are the centers of mass? What sounds do objects or actions make?

The world-builders can also use vectors to direct the user through the environment. They can be as blatant as arrows, or as subtle as a door knob.

Time and motion are vital to engaging the participant in a virtual experience. Because such experience is based on lines of program which must be read by a computer, and because technology determines how fast those lines can be read, time becomes a serious determinant in the action.

Zettl describes the present as "not so much a fixed address on the time continuum as a mode of subjective time." (Zettl, 249) Clearly VR occurs in the present. Great effort is taken to preserve the feeling of real time; no matter when the program was written, the action is taking place now.

Virtual time is subjective time. If a VR user is properly immersed in the environment, s/he has no interest in objective time. The only factor of vector magnitude that would apply, however, would be event intensity. The events taking place in the virtual world should involve the viewer with their energy; in an interactive, immersive environment, events cannot come too thickly and they can have no real relevance, that is, no emotional significance, for the participant. Too many shifts and the closeness of the viewpoint can make the action unbearable; the simple, mathematical fact of frames per second has a definitive effect on the speed at which events can present themselves.

Because human visual perception focuses on movement, the user's attention will wander if movement is missing; movement is required for immersion. Where there is apparent movement in the event loop, where the user is walking or otherwise ambulating through a virtual environment, s/he experiences figure-ground reversal. Such perceived movement is taking place while the user is sitting in a chair, or standing at a specific point, burdened with accoutrements, and probably trailing wires to stationary equipment; the illusion of movement must come from manipulation of viewpoint, but the movement appears to be in the backdrop, the ground.

What, actually, is moving, and what is the stable environment? You are encouraged to forget about the machines, to forget where you really are in favor of being there; but what is your frame of reference for perceiving motion there? If you are sitting down, or standing still while your point of view is running or flying, you have motion paradox.

The experience may or may not be a linear one. The world-builder can provide doors to be opened or side trips to be pursued. The user can fly through the virtual world at varying rates of speed, which can set the mood, or overall ambience, of the particular program. For example, a flight could be slow, relaxed, and soaring, or headlong, a rush over hills and valleys. A walk must proceed at the user's rate and take into account the possibility that the user will choose to stop and gawk, or wander around.

An object can move in virtual space, but it can only do so if it has been programmed with an animation protocol, and then the speed at which it moves is determined by the event loop and how quickly it cycles.

In addition, because movement in VR takes place on what is, effectively, a television screen, regardless of its size, Zettl's principle that the frame is always in motion applies thereto. The program that runs it is constantly in motion as well.

Pimentel & Teixeira discuss the possibility of theatricalizing the virtual environment by using camera angles and other pictorial techniques, like fade-ins and close-ups, to make it more engaging (Pimentel & Teixeira, 120, 153). I have my doubts about this since camera angles represent viewpoint, and viewpoint is how one moves through the virtual environment. Changing viewpoints like camera angles would have the user bouncing all over virtual space, which would be confusing as well as possibly nausea producing. A virtual world is, essentially, a one-camera world, and the user is the camera. The world builder must allow time in the event for the camera to get from position to position in an orderly fashion.

(To continue, please click here.)