by
Jeff Grubb
08-13-10 | 09:22 PM America/Chicago
The 3DS wowed the crowds at E3. The 3D handheld certainly had the most buzz coming out of the show. Of course, people have been most amazed by the 3DS's ability to do 3D images without the use of glasses, and - while the effect is amazing - it is pretty straight forward in how it is achieved.
The video above explains the basics, but if you are more of the reading-type, then here it is laid out as simply as we can put it.
Let me first explain how 3D vision works. The truth is that each eye only sees in 2D, the brain has evolved to composite those 2D images into a single 3D image. The only requirement is that the source images must be taken from a slightly different perspective. The slight difference must be equal to about the average distance between human eyes.
![](http://i1014.photobucket.com/albums/af268/JeffGrubb/CameraOneCameraTwo.jpg)
The image above is a cross-eyed 3D image. If you cross your eyes so that your left eye is looking at the right image and your right is looking at the left, then you will be able to see this image in 3D. For more information on how to see cross-eyed 3D go here.
With almost any videogame getting the two source images is fairly easy. Videogames have all of the requisite visual information to create two 2D images from a slightly different perspective. The hard part is getting the correct image to the correct eye.
That is the trick. The eyes can't just compile two images on their own. The correct image must be viewed by only the correct eye. The left perspective must be viewed by the left eye and vice versa. For this problem there are a plethora of solutions.
One of the oldest methods is anaglyph glasses. These glasses put a cyan and red lens on opposite eyes. Then two projectors with corresponding cyan and red filters project the two source images onto one screen. The cyan lens blocks cyan light and the red lens blocks red light, ensuring that each eye only sees the correct source.
![](http://i1014.photobucket.com/albums/af268/JeffGrubb/3-d-glasses-traditional.gif)
The way that Nintendo tackles this problem without glasses is pretty ingenious, but also has its limitations. It is called a parallax barrier. A parallax barrier works like a vent. It is a filter placed over the screen that precisely directs one image to the left and the other to the right with a separation of a few degrees (equal to the distance between the average human's eyes). It does this using tiny shutters.
Basically, it is like a pole sitting in front of a light source and your right eye can see behind the pole, but the left eye can't. Only the scale is so microscopic that your brain doesn't realize the pole is there and combines the two images as if they were one.
![](http://i1014.photobucket.com/albums/af268/JeffGrubb/2DScreenMine.jpg)
The way a standard 2D screen emits light.
![](http://i1014.photobucket.com/albums/af268/JeffGrubb/3DScreenMe.jpg)
The way a parallax barrier emits light.
To recap:
- 1 Two 2D images taken from a slightly different perspective
- 2 Both are emitted from the 3DS's screen
- 3 The left image and the right image occupy every other vertical column of pixels
- 4 The images are then directed out of the screen by the parallax barrier
- 5 Where they hit the eyes and are combined into a single 3D image
Of course, there is a drawback. In order for the two images to hit the eyes correctly the viewer must have their eyes placed in the screen's sweet spot. The sweet spot on the 3DS will be 1 - 2 feet out and directly in front of the screen. This is why we haven't seen this technology take off in televisions and movie theaters, but we may soon be seeing it in mobile phones and computer monitors.
http://www.kombo.com/features/How_the_3DS_Works/#