Some virtual reality games are advertised as being created from the ground up for virtual reality. What does this mean exactly?
What are some of the differences between developing a 3d pc game and a vr game?
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Games for PC are often develop with keyboard and mouse in mind. That is not the usual interface for VR games.
Even if we treat a VR controller as a pointing device, the expectation is that you will have one on each hand, and you would use them to interact with the game world in a believable manner.
For example, you may do a key-press to open a door in a PC game… on a VR game, it is expected that you actually reach with your VR controller to interact with the door (and yes, we need to consider that the play might limited real space to play). For another example, if a PC game you would press a key to reload your weapon, on a VR game you do a gesture to pull a magazine and you put it in the gun.
Similarly, while the mouse is often the solution to control the camera in a PC game, on a VR game the expectation is that you move your head. Will come back to the camera. Yet, while we are talking about controls, you don't have buttons to agree or disagree on a dialog, but a good alternative is to gesture with your head.
A much bigger consideration is locomotion. On a PC game, you probably just press W to move forward. But moving around in a VR game is a design challenge that must be considered from the start. A common solution is to have teleportation in the game. Other solutions include placing the player inside a vehicle so that they can navigate by controlling the vehicule, making the game on rail (as in rail shooters), having the whole game in a small area (for example defending against waves or enemies), or using some gesture to move around (e.g. moving the VR controllers as if you were skiing, or as if you were
playing maracas running).
Your VR game is very likely going to be first person. That is the player expectation. And while any 3D PC game could be modified to support a VR headset, a VR game has some extra considerations…
In particular, we want to set a confortable head height for the player. And this often means that there will be calibration step.
Another expectation of VR games is that the control of the camera (moving your head around) will never be taken away from the player. And that means that when you are playing a cut-scene, the player must still be able to look around. And this increases the challenge of making sure the player pays attention to what we want as game designers.
Plus, as designers it is more interesting to do exposition in a diegetic way (and rely somewhat less on the cinematic language, and avoid not diegetic HUDs and menus). Sudden camera cuts, or things floating in midair can break the immersion.
In fact, keep in mind that a person is experiencing the game in a headset. You could get the player disoriented, dizzy (some people are more susceptible to that than others), or simply with a bad headache.
Ultimately, if you are designing for VR, you want to provide a good experience for VR players. When a game is advertised as being created from the ground up for virtual reality, they are promising a good experience for VR players, or at least one better than simply having support for playing a PC game with a VR headset.