Monocular Depth Cues and Virtual Reality

We already know that our monitors show a single image effortlessly. 3D, on the other hand, when viewed on a 2D screen looses depth perception. We all have tried 3D glasses in cinemas, and if you are gamer then you must have also played Crysis with 3D glasses using Nvidia 3D tech. But, rendering a virtual scene in Virtual Reality is quite challenging. So, researchers and companies came up with a solution to immerse you completely by tricking your eyes using polarized lenses.

VR glasses contain polarised lenses which show two images, one per each eye and the advanced version contains head tracking and positional tracking for helping you getting immersed with more precise and realistic input methods.

Our eyes uses cues to perceive depth. Cues are used for the depth perception that involves the use of only one eye. When using monocular cues you can determine size, shape, motion and what the object is. Cues also use interposition to locate objects distant from yourself. Using these cues we determine how far two objects are from each other, which isn’t possible using 360° stereoscopic imagery/videography. Using monuclar depth cues in Virtual Reality, we can get a better perception of scale, size, depth and height.

If you have ever seen a plane landing, you would have noticed that the plane seems to be getting bigger as it comes closer to you. Monocular cues provides the same illusion of depth from motion just like the plane. This adds significant immersion layers while you are in Virtual Reality as compared to 2D screen in real world coordinate.

Presence is a psychological state or subjective perception in which even though part of all of an individual’s current experience is generated by and or filtered through human-made technology , part of all of the individual’s perception fails to accurately acknowledge the role of the technology in the experience. — International Society for Presence Research, 2000

Drawing 2 images or rendering real time geometry, one per eye, also adds to the presence but at the expense of GPU overhead. There are experiments available such as single-pass rendering which renders 3D scene simultaneously on both eyes at once which reduces GPU and overhead dramatically.

In visual perception, the kinetic depth effect refers to the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving. In the absence of other visual depth cues, this might be the only perception mechanism available to infer the object’s shape.

Monocular depth cues provides kinetic depth effect, for example, a point light source falling on one side of cube creates shadows, helping a users eye to perceive a more realistic depth effect. Monocular cues also provides perspective, which is defined as the property of parallel lines converging in the distance, at infinity. An example would be standing on a straight road, looking down the road, and noticing the road narrows as it goes off in the distance. This sense of perspective helps create VR worlds which is life size and life like virtual environments.

To conclude, Monocular depth cues plays an important role in 3° degree of immersion and currently Google & Oculus are researching on ways to increase visual perception in HMD’s lenses.

This article was first published on VirtualSpaces.


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