Virtual Reality has come a long way since its first conception. From large uncomfortable contraptions in the early 1960’s through to lightweight HMDs released in 2016, technology advances allow us to create more immersive headsets each year. Recently we seem to have hit a wall, where we are struggling to solve a few issues and move into more immersive HMDs. The issues mainly revolve around Field of View (FOV), pixel density, spactial audio, and Field of Depth (FOD).
Above: The StarVR HMD has angled displays.
Field of View (FOV)
Humans can generally see a FOV of between 200-220 degrees horizontally, and although we don’t focus on our peripherals it is noticeable when they are blocked. We become aware we are in an enclosed space. The two major players in PC VR, Oculus Rift and HTC Vive, offer a FOV of about 110 degrees, and the PlayStation VR headset only about 100 degrees. The limited FOV means it is possible to see the black outline of the screens, which breaks your immersion. These headsets all use the same setup with dual display screens mounted side-by-side (one for each eye), and this may be what they need to change to create a realistic FOV.
The StarVR headset features up to 210 degrees FOV, and has dual display screens mounted at an arrow-head angle. While still in development by Starbreeze Studios and Acer, this headset allows peripheral vision and therefore doesn’t break your immersion. The higher quality angled displays also alleviate the pixel density issue.
Above: Difference in FOV of StarVR and other HMDs
A higher density of pixels means a clearer image, and no ‘screen door’ effect (when you can actually see the fine lines separating pixels). This is more obvious in HMDs than other screens, due to the display being so close to your face. Low pixel density also makes everything look slightly out of focus, and is very noticeable with detailed objects and written text. The end goal is to improve pixel density up to the resolution your fovea sees. There is no need to improve past this point, as your eyes will not notice the difference.
The fovea is a spot in your eye that sees the sharpest, it is the point that your 20/20 vision is calculated. It also has a small focal point, which is why everything around what you focus on is blurred. Because of this, VR developers are starting to bring in ‘foveated rendering’ alongside eye-tracking. Foveated rendering is a process that blurs the outside of the displayed image, just as your eyes naturally do. It saves on GPU power, which is one issue encountered when using denser displays. Rendering while using eye-tracking makes this process more natural and accurate.
Above: Example of foveated rendering. Image from: roadtovr.com
Spacial audio allows for total immersion, where sound can match your virtual surroundings. In the real world, your ears pick up sounds in a 3D 360-degree environment. Sound bounces around objects, through different mediums, and can move within the space. Surround Sound changed the way sound was mixed for cinema films, but this method is not suitable for VR experiences as sound naturally comes from all directions, not just five or seven fixed locations. Now, developers are able to allocate sounds to particular positions or objects. It creates the illusion of presence, and without it you can feel disconnected from the experience. It brings in a feeling of depth to the virtual space.
Field of Depth (FOD)
The FOD represents the depth of the space you are in, and has a lot to do with foveated rendering and eye-tracking. If you want to make something look realistic, the details need to be there. If everything has the same level of blur, it’s noticeable you are looking at a screen. The same applies to audio.
Above: FOD shown using foveated rendering. Image from: roadtovr.com
Our experience of VR can only be as good as the HMD allows, and the goal is to match the level of immersion we experience in the real-world. With so many small experimental VR HMD developers working to tackle these problems, these issues are believed to be solved within the next five years.
Header Image: roadtovr.com