Recently, we have been tasked with developing a number of VR applications, which use Google Cardboard including: a VR car configurator with 360º drone footage and a 360º image of the car’s interior; 360º property view showcase; and a 360º ice skating experience.
But, during the development phase of these products, we noticed that not everyone was seeing the same thing. In fact, some people were seeing double, a blurred or low res image. Why? Because the stereoscopic effect required to make VR work, relies on precise alignment which is simply not achievable with a universal cardboard viewer.
The viewing problems are typically the result of a mismatching interpupillary distance (IPD). IPD is the distance, centre-to-centre, between the pupils of the user’s eyes which will vary user to user.
Some platforms such as Gear VR and Oculus allow you to calibrate a user-specific IPD setting, but not Google Cardboard. It is forced to choose a happy medium at 64mm, which is between a male and female averaged IPD. If this happens to be quite different to the current user, they are likely to see some blurriness.
IPD however is not the only issue with viewing an experience through Google Cardboard. As a universal viewer in a world of varying phone screen sizes -with such small accurate dimensions required to create a flawless VR experience - a discrepancy of over an inch in compatible screen size is bound to throw it off. The first generation (V1.0 Cardboard) struggled to accommodate devices with a 4.7” screen or bigger, which was revised in V2.0, but now makes smaller screened devices have an ugly black border around the outside when viewing.
Google Cardboard also relies on the user to centre their phone when placing it into the device. If the phone is not correctly aligned, this causes visual problems that can inhibit the convergence of the two lens images. Finally, Google Cardboard is an open sourced viewer; Google do not make them, 3rd party manufacturers do. We rely on the quality control of the manufacturer to ensure factors such as clarity of the lenses. In our projects using Google Cardboard, we are often ordering from different manufacturers in China and we have seen quality discrepancies even across units within the same batch.
It’s easy to blame the Cardboard for these viewing issues, but during our most recent project we also noticed a double reticle.
A reticle is a visible circle placed in the user’s centre of the view in VR that can be used to trigger actions by looking at objects in the virtual space.
When developing our app, we noticed that the reticle appeared to be out of focus and could occasionally fail to converge into one image, appearing double at times. This is a vision issue known as “vergence-accommodation conflict”. There are studies and journals explaining this effect in scientific detail, but we like to think of it as your eye’s ability to focus (based on distance) is being tricked by the same thing that allows VR to give the illusion of depth and distance. Hold an object close to your eyes and focus on something far away and you’ll notice that the object close to your face is now out of focus and split in two. Imagine this in VR. Your eyes are being tricked into seeing screen content at different distances, which are all actually the same distance from your face. Essentially, your eyes and brain can’t process this and you become aware of the doubling-up of the objects close by. For our project, a quick-fix approach worked well for us. We brought all of the in-app VR assets closer to the user, reducing the extremity of this effect.
All this sounds like doom and gloom for Google Cardboard, but the reality is far from it. These effects are relatively minor. In our experience the vast majority of users do not notice these minor flaws and have a great VR experience. Google Cardboard was originally released as a prototype object to show how simple and low cost VR could be. As a result, demand for it exploded. It now finds itself competing against devices that cost over 100x what it costs and is still holding its own. Even the more expensive headsets are yet to find a good solution for vergence-accommodation conflict and IPD.
So when you next put on a VR viewer and think, am I seeing double? The answer is you probably are, but that’s ok because with increased interest and demand for VR come more opportunities for developers to work to make this technology better than ever before.
This blog post was written by Jack Chalkley and Emi Mitchell.