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Stereo Mode Implementation

So far, the quality of this mode depends on how correctly the distances and proportions of the 3D scene are implemented in the specific game.

Games based on the Source engine (developed by Valve Software) and Cry Engine (by Crytek) have a correct 3D scene. The effect is impressive in Left 4 Dead as the buildings, objects and characters all become so real that you want to reach out and touch them. As a single drawback, there were odd artifacts in bright spots of light when I was walking with a flashlight.

There was an odd effect in Prince of Persia. Although this game has the highest compatibility level in Nvidia’s list, I did not feel much of stereoscopy in it because of the specific contours around the characters. The brain perceives the characters as just drawn rather than three-dimensional. You can focus on the picture to see the third dimension, but as soon as you relax, the game world becomes flat again.

The perception of the stereo mode in strategies depends on the specific game, too. If there are some labels attached to the units (for example, labels showing the unit size in Heroes of Might and Magic), they prove to be hanging somewhere between you and the unit, which is inconvenient. The game developer obviously did not think of any stereo modes and did not assign a specific depth for such labels. If there is nothing like that in the game, the game world looks just splendid. You get a feeling that there is a tiny real world in front of you, with tiny factories and tiny tanks. Sometimes I caught myself wanting just to take a tank with my fingers and move it on the map where it was needed.

I did not notice any doubling or ghosting of the image resulting from the left eye seeing the residue of the right-eye image (this effect could be seen on the iZ3D monitor and was really irritating).

It is assumed that the lenses in shutter glasses are switched alternately. When one becomes transparent, the other is opaque, and vice versa. Such a swift switching is no problem for the simple liquid-crystal shutters, but may be a problem for LCD monitors. As I found in my test, the 120Hz SyncMaster 2233RZ took an average 3 milliseconds to switch between halftones. It means that if the lenses switched instantaneously, one eye would see the fading-out remains of the picture meant for the other eye for an average of 3 milliseconds. And there are also RTC artifacts that take even more time to disappear.

To check out Nvidia’s solution of the problem I measured the process of lens switching by placing a photo sensor connected to an oscilloscope on one side of it and a light source on the other side of the lens. The high level of signal in the oscillogram corresponds to the period of time when the lens is translucent.

As you can see, the lens is translucent only 2 milliseconds out of each 16.7 milliseconds. That is, most of the time both lenses of the 3D glasses are shut and the monitor has 6.3 milliseconds (because the frames go at a rate of 120Hz, i.e. one frame each 8.3 milliseconds) to change the picture.

Unfortunately, such a low on-off time ratio (with a short period of translucence and a long period of opaqueness) leads to a 60Hz flicker. The perception of the flicker depends on the particular person. Some people may take no notice of it while others will have sore eyes, but the flicker is indeed perceptible.

Flickering is less conspicuous in dynamic visual content such as games and movies (we watch CRT TV-sets at 50Hz, for example), and the glasses turn off when you leave a 3D application. Here, in our labs, the opinions differed. I could see the flickering well enough as soon as I looked away from the monitor at a light wall and sometimes noticed it in games, but my colleague did not see any flicker at all.

To reduce the flicker, Nvidia recommends setting the maximum brightness on your monitor in games (the backlight lamps do not flicker then, which can save you from possible pulsations of brightness due to the overlapping of the two frequencies) and try to avoid daylight lamps with electromagnetic ballast that flicker at the double frequency of the mains.

Besides, the glasses reduce the intensity of light greatly, making the surroundings dim. Therefore the monitor must have a good brightness. The SyncMaster 2233RZ ensures over 300 nits, however, so this was not a problem. The glasses reduce the brightness of the ambient light, too. So you can play normally even under good daylight.

Nvidia’s 3D glasses do not have a negative effect on the monitor’s color reproduction or viewing angles.

 
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