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With the announcement of the Steam VR powered HTC Vive at GDC, there are now two very different types of interaction to think about when creating VR games and experiences.

Both the Oculus Rift and Sony Morpheus headsets are designed to be primarily used when stationary. Oculus gets users to sit down whenever they demo their headset in public, facing forwards.

Sony often demonstrates the Morpheus standing up, but players need to remain within a fairly small area, and normally face forwards towards the camera most of the time. I suspect that Sony expect most of their consumers to use the Morpheus whilst sat on a sofa.

With both headsets, you can move your head within a relatively small area, you can rotate your head around, but the hardware works best when you are looking forward. In practice, since most people will play them whilst sat in a chair, your body will tend to stay facing in one direction all the time. Even when standing in Sony’s Heist demo, players face the camera and their movement is limited.

The Steam VR system is different. You are free to walk around, rotate and move within this area, just like you would in real-life. There is no notion of ‘forward’.

The Steam VR system is different. With the HTC Vive, you can define a fairly large area of empty space (demos have been shown using 4.5m x 4.5m) to move within. You are free to walk around, rotate and move within this area, just like you would in real-life. There is no notion of ‘forward’.

The system elegantly warns you when you get close to the edges of your pre-set space, and the long, tangle-free cable is much less of a problem than you’d imagine. The position and rotation of the headset and the two handheld controllers is tracked with millimetre precision by Steam’s Lighthouse tracking technology.

So what are the advantages and disadvantages of these approaches, and how can you design your VR game to work with both systems?

Sit-down, face-forward VR is by far the simplest approach, best demonstrated by the Morpheus. Plug it into your PS4, stick it on your head and play. Simple!

In comparison, setting up a couple of Lighthouse boxes at the right height, clearing a space, plugging everything in to your PC and calibrating it all, is likely to be more time consuming. Plus, there is an argument that playing games whilst being sat down is a more relaxing experience and that some people won’t want to stand up and walk around for long periods of time.

However, the pay-off is that walk-around VR can provide a stronger and richer sense of presence than face-forward VR.

What is presence?

Presence is the belief that you have been teleported to another world – fooling your subconscious into believing that what you are seeing and hearing is real. With presence, you forget the real world, and believe you are actually in another place.

Presence is an analogue scale, ranging from “This world feels completely fake” at one end to “I am totally convinced I am physically here” on the other end. You don’t need 100 per cent presence to have an amazing and emotionally powerful time – in fact, no VR headset currently offers 100 per cent presence. However, being able to move physically around a virtual space rather than using a controller increases the feeling of presence significantly.

Interestingly, too much presence can be a bad thing – the more presence you feel, the more you notice tiny details which aren’t correct, and these can take you out of the experience. So as a developer, unless you can make things perfect, it may be better to set a lower ‘presence’ target, and hit it well. A good example of this is not having a body for the player unless you can do it perfectly. A bad body is much worse than not having one at all.

The Vive controllers and PlayStation Move controllers also have a big advantage over gamepads. The natural instinct of players when they use a VR headset for the first time is to reach out and try to grab things with their hands. With tracked controllers you can do this – including fairly complex interactions such as picking up a bottle, throwing it into the air and catching it again with the other hand. You won’t be surprised to hear that this kind of interaction feels much more realistic than pressing a button or a stick on a gamepad. Combine this with the free movement that Steam VR offers, and it’s a very special experience indeed.

You don’t need 100 per cent presence to have an amazing and emotionally powerful time – in fact, no VR headset currently offers 100 per cent presence.

Movement is one of the biggest game design challenges that we’re facing. Some people find using the right-stick of a controller to rotate whilst simultaneously rotating with their head quite unnerving. There are a variety of control schemes that help alleviate this, but it’s still unclear what will emerge as the best standard.

In contrast, on the HTC headset, you rotate with your body, which is perfectly natural. This means movement is a better experience and the small percentage of people who suffer simulation sickness with VR movement is reduced even further.

The big challenge with walk-around VR is how do you explore environments that are bigger than your play space? What happens if the cargo bay in your game is 5m x 5m and you only have a 2m wide space available in the real world? How do you navigate an open world? Again, these are all solvable problems, but it’s likely that early games will try to solve them in different ways until a standardised method appears.

There are lots of potential solutions all these issues and user testing them is one of our key goals at the moment – we don’t have all the answers yet, but we have a much better idea than we did only a short time ago! This is one reason why VR development is such a fascinating area – there are so many unanswered questions and new game design challenges to sink your teeth into.

VR is a huge uncharted space, and I think our team all feel like explorers at the moment.

nDreams is a UK developer that focuses on virtual worlds and virtual reality. You can find out more about the studio at www.ndreams.com