Translation of Daniel Allen's article (here).

The omnipresence of Unity " and " Unreal in the development of traditional games, can give rise to experienced developers, the desire to embark on the design of a virtual reality game.
Indeed, it is an emerging market where old or common concepts can become original and new if they are built in virtual reality.
However, designing for virtual reality is not easy…
There are many fundamental concepts that change in the design made in virtual reality. We will try to deal with the most important characteristics, learned to " Block Interval that exist between the creation of PC games and those for virtual reality.

Comfort

Comfort is the criterion that requires the most research. It constitutes the new evolution to take into account in the user experience: Any game without a comfort option in the menu exposes itself to a negative reception on the part of users.
Some users have iron stomachs while others are extremely sensitive to movements performed in virtual reality. For these "fragile stomachs", it will be necessary to provide tools allowing them to modify the experience according to their degree of tolerance: which can result in a "blink" mode (which eliminates the animation between two points if it becomes too difficult).
This type of menu/mode as well as numerous tests will significantly improve playing comfort.
We invite you to take a look at “ Triangular Pixels » and its comfort options.
[youtube=https://youtu.be/0r4PkBYc_fk&w=640&h=385]  

Interface

We keep repeating it: we can no longer "throw" images in the face of the players as we did in traditional games. Interfaces should now exist inside the game itself.
Buttons and menus will also need to be changed to suit the field of view. For the current generation of virtual reality headsets, the resolution is rather low (compared to a PC screen), the texts and buttons must therefore adapt by being designed in a readable and identifiable size.
Many other characteristics come into play: Mike Alger gives us a general overview in this video:
[youtube=https://youtu.be/n3b8hZ5NV2E&w=640&h=385]  

sound and music

Sound is a key factor in achieving a successful immersive experience: It is an element that designers and developers must imperatively integrate based on the atmosphere of the game and the different stages of it.
Indeed, if you only position music and sound effects without really taking into account the game itself, the user experience will be impacted.
The time when a single person created a good game is soon over, now the skills are multiple and must be coordinated: Programs like wwise allow us to work on these variables.

Mouvement

Virtual reality could “kill” the WASD directional keys: Moving a player around is more complex in virtual reality because there are no more barriers between the user and the environment (such as the screen of 'computer).
The approach to movement will depend on the type of game you want to create. Games with ships, cars seem to work very well in virtual reality because the environment moves around the vehicle, while a simulated body is not as immersive.
You have to put in place many tests and not rely on the achievements in motion that you can have in traditional games. In particular, make sure you have taken into account the fact to be standing and not sitting.
If you are doing a live game be sure you understand what type of space size options you have. Take a look at what " Stress Level Zero found for his live testing.

Interaction

Virtual reality can announce the end of the mouse and the click to interact with the elements. A wide variety of device-dependent approaches now exist. With more immersive tools like the almost realized "oculus Touch", or the HTC live controllers, the interactions will be much easier to understand.
At the same time, we are faced with the challenge of working either with keyboard/mouse or with a controller (like the X-Box One controller which will be embedded in the Oculus Rift CV1 devices). Mike Alger created a great video on virtual reality interactions:[youtube=https://youtu.be/id86HeV-Vb8&w=640&h=385]

Normal Maps

If you don't know what Normal Maps are, catch up here.
Normal maps don't work very well in virtual reality.
This is because the eyes are good at picking up depth information: VR is stereoscopic by default, we see normal maps as flat or lacking in depth information. This attests that the geometry bears much more the weight of immersion than the “normal maps”.
It is probably best to rely on normal maps only for objects far from the user, as the parallax effect will be negligible beyond a certain distance.
Please note, we are not advising you not to use normal maps, you just have to take into consideration that these are not ideal for translating the depth on objects close to the user.

Detail of 3D models

Virtual reality allows the player to be closer to the objects that make up his game universe.
This implies that more work needs to be done to make the objects look real and detailed. The amount of well-designed 3D models needed for a strong experience will be even greater than in a traditional game.
Users expect to see very realistic close objects, so they need to have a high polygon and texture ratio and be fully interactive. You can decrease the budget on distant objects, but not on near objects.

TESTS

User testing will be even more important than before. We will not only have to make sure that our games do not make our users sick, but also that the environments we have designed make sense in three dimensions.
Do users know where they can go? Are there any spatial or virtual clues to what they can do and where to look? If you don't test your VR games on 'real' end users, you will most likely release a game riddled with issues.

CONCLUSION…for now

There are so many other topics to cover but unfortunately this is just a blog post. We will cover more of our learnings in the future.
We hope that this information will help you better understand virtual reality content.
If you liked it, feel free to share.
Anne Pedro – UX-Activist @UXRepublic

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