In Memory of the video game Lost Posts est désormais compatible avec l'extension FastNews.kiwi disponible pour votre navigateur. Avec cette extension, vérifiez s'il y a des nouveaux sujets sur ce forum en un clic depuis n'importe quelle page !Cliquez ici pour en savoir plus.
Posted: Tue 5 Apr - 22:07 (2011) Post subject: Nintendo 3DS : OK explain to me 400 x 240
The parallax barrier is a transparent LCD screen that sits on top of the regular screen. In that sense, the screen is dual layer (that is, the parallax barrier screen on top and, underneath, the gameplay screen). When you turn on the 3D, that overlay LCD screen draws the parallax barrier. This LCD barrier directs the light of the odd numbered pixels to your right eye and the light of the even numbered pixels toward your left eye. Watch this video someone posted to YouTube to see how that works:
Did you see how the pixels in that video are elongated? They're not literally that proportion, since on the 3DS they're only twice as high as they are wide, which I'll prove to you in a moment (just believe me for now). When the barrier is on, your right eye sees the odd pixels, while the even numbered ones are blocked. Vice versa for your left eye. The odd pixels and the even pixels aren't necessarily the same image, because the perspective is slightly different (just like when you switch back and forth between looking out of one or the other eye) and this is where stereoscopy comes into play: your brain merges these two different images and you perceive a 3D image.
Now, when you turn off the 3D mode to use 2D mode, the parallax barrier screen goes completely transparent; nothing is directing the light and all you see is all of the pixels of the underlying gameplay screen. This is where those alternating rectangular pixels are showing the same color (remember 1|2, 3|4, 5|6. etc). Since the pixels are half width and full height, every two horizontal pixels and one vertical pixel equals a square shape.
Technically it's 800x240, but since every other horizontal pixel is doubled to create the equivalent of square pixels, it's essentially the same as seeing a 400x240 image. You could easily erase the even numbered pixels (since they're just duplicates of the odd pixels) and transfer that 800x240 2D image to a 400x240 screen and it would look no different at all. Hence, why the 800x240 screen is the same as a 400x240 one in 2D mode.
Finally, the proof. Think of screen aspect ratios, like 4:3 and 16:9. Take a common 4:3 screen resolution like 640x480 and divide each screen aspect with its corresponding pixel row:
640x480 4:3 aspect ratio: 640/4 = 160 480/3 = 160
See how you get the same answer? This means that each pixel is square: the same width and height. You can do the same calculation for other common 4:3 aspect ratio resolutions (800x600 and 1024x768) or 16:9 ones (1280x720 and 1920x1080). You'll get different numbers, but it doesn't matter what the answer is, as long as both numbers are the same.
Now, let's consider the 3DS, which has a 5:3 aspect ratio: 400/5 = 80 240/3 = 80
So at 400x240, the numbers are the same, which means square pixels. But what about 800x240?
800/5 = 160 240/3 = 80
They're different. SO, that means that the pixels obviously aren't square. The fact that the horizontal number is twice that of the vertical number means there are more of them packed into the same horizontal space.
Of course, you don't need to do all that math. Just use basic logic: 800 is over 3 times the quantity that 240 is and anyone can clearly see that the screen isn't 3 times longer than the height. At 800x240, the only way the pixels could be square (rather than rectangular) is if the screen was actually twice as long as it currently is.