Google Cardboard changed the way most people think about VR. For a couple of dollars in materials anyone could turn their smartphone into a VR device. Google developer Shanee Nishry provides a brief overview of how the Google Cardboard technology works.
As Nishry puts it Cardboard creates a window into another world. It allows you to travel to this other world with the help of your smartphone. It does this using a combination of visual immersion, tracking and input which produces virtual reality.
In order to make the user feel like they are in the world they need to feel like they are visually immersed. To achieve this you need to focus the viewer’s field of vision. The lens focus the viewer’s natural wide field of vision onto the screen. Now all the viewer can see is the screen.
To make the immersion plausible it needs to have depth. To give them that depth they are shown in a split screen configuration. There is a slightly different image presented to each eye. This is because each eye sees the world from a slightly different perspective. The camera is slightly offset which creates a stereoscopic effect presenting a 3D virtual environment.
Next we have the problem of distortion. The lenses cause distortion to the image known as the pincushion effect. To fix this barrel distortion is applied in post production. This offsets in the pincushion effect.
The users needs to move in the virtual world like they would in the real world. Virtual movement needs to correspond with real moment. Luckily phones already have an accelerometer and gyrometer. Using these Cardboard can track head movements.
Input is how we interact with the virtual world. You could connect a game controller to the phone but Cardboard has designed a more integrated solution. Cardboard headset have a magnet on their side. When the magnet is moved it causes a distortion in magnetic field. The magnetometer then enters this as input which in turn triggers an action.