Game Development Reference
In-Depth Information
As you can imagine, the main disadvantage of this technology for gaming would be that
you have to ensure the frame rate stays relatively high. You are now rendering twice as
many images as you normally would require. We'll discuss more about the rendering
pipeline later. Also related to frame rate is the refresh rate of the display. As each eye is
really seeing only half the frames, the overall frame rate is half whatever the refresh rate
is on the screen. Older displays have refresh rates at 60 Hz and effectively halving that
can create issues with eyestrain; however, new displays support 120 Hz refresh rates so
that halving it still allows for smooth display. Also, the display will seem much dimmer
with the glasses on, as your eyes are seeing, on average, only half the light they normally
would. As you can see, dimness is a common problem among 3D display technologies.
The main advantage is that you don't need a special display. As long as your display is
capable of the required refresh rate, then you can retrofit it with a pair of LC shutter
glasses and get 3D display out of it. Nvidia released such a kit in 2008, called 3D Vision,
that is relatively popular. Graphics cards are capable of automatically converting the
depth of the object in the model world into a parallax so that older games can also be
rendered in stereoscopy. This is something to consider as you design your next game
and something we'll touch on again in a moment.
Autostereoscopy
While the newer 3D technologies are a far cry from the 3D of several decades ago, they
still rely on people wearing glasses to view the image. This means the displays can never
be used in a casual setting such as an arcade or street advertisement. Also, the younger
segment of the gaming population might break or lose the glasses. Having to put on
glasses to view the 3D images also provides a signal to your brain that what you are
about to view is optical illusion. Put on the glasses, and your brain is already thinking
that this isn't really in 3D.
Autosterescopy endeavors to create the illusion of depth without the aid of any glasses
or other wearable device. The first and most common way it does this is by introducing
a parallax barrier between the display and the user. As discussed earlier, parallax—and
by extension, binocular disparity—is what gives our brain a main source of information
on depth. A parallax barrier uses the fact that each of your eyes sees things from a slightly
different angle to separate the two channels required for stereoscopy. Physically, the
barrier is a layer placed in or on the screen with a series of very precisely cut slits. Because
your eyes are not in the same spot, the slits reveal different pixels on the screen to each
eye. A basic illustration of this method is shown in Figure 24-9 .
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