Game Development Reference
In-Depth Information
to correct the color and account for some fuzziness. One example is the patented Col‐
orCode 3D, which uses amber and blue filters. The advantage of this system is a nearly
full color space and a fairly good image when not viewed with the glasses.
Anaglyphs fell out of favor with movie and game producers when polarization techni‐
ques came into maturity. These produce better color reproduction and reduce eyestrain.
However, given the relatively inexpensive glasses required and that nothing special is
required of the display other than that it be capable of displaying colors, anaglyphs have
had a resurgence in printed material and online.
Linear and Circular Polarization
As polarized light plays a very important part in the largest 3D displays, movie screens,
we'll review what polarization of light means and how to accomplish it. Light can be
thought of as an electromagnetic wave traveling through space. Let's begin our discus‐
sion by considering a common light bulb. It emits electromagnetic waves in all directions
and is nominally “white.” An electromagnetic wave oscillates perpendicularly to its line
of travel. This is called a transverse wave . In comparison, sound waves oscillate in the
same direction they travel, creating regions of higher density. These are called longitu‐
dinal waves . Only transverse waves can be polarized because only transverse waves have
oscillation in multiple orientations. Going back to our light bulb, it is emitting “dirty”
light in that the electromagnetic waves are all at random orientations.
Most sources of electromagnetic radiation (i.e., light) are composed of many molecules
that all have different orientations when they emit light, so the light is unpolarized. If
that light passes through a polarization filter, it leaves the filter with the oscillations in
only one direction. In fact, there are two types of filters. Linear filters produce oscillations
in one direction. Circular filters (a special case of elliptical filters) create circularly po‐
larized light that rotates in an either righthand or lefthand direction. As circular filters
depend on linear filters first, we'll discuss those now.
The simplest and most common linear filter is the wire-grid polarizer. Imagine many
very fine wires running parallel to one another with small gaps between them, as shown
in Figure 24-7 . When unpolarized light hits the wires, the oscillations that are parallel
to the waves excite the electrons in the wire and move them along the length of the wire.
This phenomenon causes that component of the oscillations to be reflected. However,
the electrons cannot easily move perpendicular to the length of the wires, so the reflec‐
tion phenomenon doesn't occur. What we are left with on the far side of the filter is a
beam of light with the oscillations all in the same direction.