July 25, 2009 at 1:27 pm
Well over a year ago I speculated on this blog about first person controls on the iPhone. I want to post an updated set of observations and opinions, largely just to collect my own thoughts on the matter somewhere where I can refer to them.
First person shooters frequently demand three different basic actions be performed at the same time time: moving, looking, and shooting. On a PC, the keyboard is usually used to move, and the mouse to look and to fire. On a console gamepad, two analog sticks are used to move and look, and shoulder buttons are used to fire. Both setups allow for all three actions to be done at the same time. The PC setup allows for far more precise aiming, while the console gamepad setup allows for analog movement.
When playing a game on the iPhone by holding the device in a landscape orientation, the setup allows for two on-screen elements to be feasibly interacted with at the same time, both of which involving thumbs. The thumbs are most comfortable in the bottom corners, and can go to the top corners fairly easily.
Thumbs obscure anything they touch.
The accelerometer can be used as a third input. Rotating the device moves the screen around, which is obvious but needs to be considered before giving the accelerometer any role in controlling the game.
Because of these considerations, the iPhone is fundamentally at a disadvantage. If the accelerometer is not used, the user can only do two of the three basic actions at a time. Using the accelerometer brings with it its own set of considerations.
The remainder of this post will list various options for controls, and weigh pros and cons in each.
If a game has several controls relegated to the corners, the parts of the screen that don't have controls can be used for another action.
See: Prey Invasion
In the tap to shoot mechanic, the player can directly tap on bad guys to shoot them.
Pros: Very quick to fire at an enemy, possibly even faster than with a mouse.
Cons: The thumb obscures the target, leaving you generally without visual feedback of the damage you're inflicting or any changes in the situation around the bad guy (such as if he fired a rocket at you while you were shooting him). Also, the thumb is fairly large, so some degree of aiming assistance might be needed (should register a hit so long as the bad guy is covered by the thumb, not just when the bad guy is precisely at the center of the thumb). The visual feedback problem might be able to be helped with a loupe: an extra viewport placed above the thumb that shows what the thumb is covering.
See: Brothers in Arms, Terminator: Salvation
The mouse pad mechanic allows the user to treat the screen like it was a mouse pad, and their thumb like it was a mouse.
Pros: High precision, frees up the screen from having a separate look control.
Cons: Thumb obscuring can be a problem if it goes too far without being lifted. Can be frustrating without a well-refined acceleration curve.
In addition to a single fullscreen control, multiple smaller controls can be placed on the screen.
See: Just about every FPS on the phone
This replicates a console-style analog stick, but on the touchscreen.
Pros: Intuitive, straightforward, works pretty darn well
Cons: Any virtual analog stick needs to be highly refined to deliver a good experience. Dead zones, acceleration curves, the size of the control, etc are all easy to screw up. In summary: difficulty of implementing well.
See: Wolfenstein 3D, iFPS
This is the same as the movement stick, except for looking.
Pros: Intuitive and straightforward. Works pretty well in practice when done correctly.
Cons: More or less all of the difficulties of the movement stick. Not the most efficient way to look. Precise aiming can be tricky if the stick is too sensitive. Turning broadly can be hindered if the stick is not sensitive enough.
See: Not aware of any on the phone
This is the same as the full-screen mouse pad, except limited to a small area of the screen.
Pros: Precise. Allows the screen to be used for a different purpose, like tap to shoot.
Cons: More likely to be finicky than the full-screen mouse pad.
See: Just about everything
It's a button. Tapping it fires your weapon.
Pros: It makes things die.
Cons: Why can't we be friends?
See: Not aware of any on the phone
Tapping this button causes your view to lock onto a nearby enemy, either for a prolonged period, Metroid Prime-style, or just at the moment you tap it, Call of Duty-style.
Pros: Big help to aiming when combined with less precise looking options.
Cons: Not as helpful for weapons that need to be led (like rockets) as it is for instant hit weapons. Exists to cover the fact that your general aiming method isn't precise.
The only way to allow the user to realistically do three things at once is to use the accelerometer. But it's really easy to screw up, so be careful if you use it.
See: Cube
This control scheme turns the phone's accelerometer into an analog movement stick. It is also morally equivalent to using infants as a baseball bat.
Pros: None that I will dignify by listing here.
Cons: Just about the most backwards thing ever. Also, I'll not want to be your friend.
See: Several games have this as an option
This control scheme turns the phone's accelerometer into an analog looking stick. It's like tilt to move, except it actually makes rational sense.
Pros: Given on-screen movement and shooting controls, the user can do all three basic actions at once.
Cons: Same considerations as all other analog schemes. Tilting the phone alters the view angle of the screen. Special consideration to sensitivity and neutral angle is needed.
See: Doom Resurrection
This is distinct from tilt to look in that tilting doesn't change where you're looking, it just moves the crosshair within the viewport.
Pros: Works very surprisingly well.
Cons: Not a complete solution to the looking action. The game needs to either eliminate looking as a full-fledged action (as in an on-rails game like Doom Resurrection) or have a separate on-screen looking control to control broad turning.
See: Not aware of anything on the iPhone, but Metroid Prime 3 on the Wii is pretty close
This combines looking and aiming into one control. The more you tilt the phone, the faster your character will turn and the further off-center your crosshair will be.
Pros: If done well (like Metroid Prime 3), it works pretty well.
Cons: If done poorly (like many other first person shooters on the Wii), it'll just be awful.
There are many options available to developers, and I don't think anyone has hit the sweet spot yet, though id has delivered very good experiences in both Wolf 3D and Doom Resurrection. This post didn't even touch on things like jumping and switching weapons, but it's long enough as is. I think the iPhone has the potential to be at least a satisfactory player on the FPS scene. It's just a matter of figuring out the controls.