Twist, Touch & Travel Touch, Twist, and Travel Harnessing the iPhone's Unique Features Glenda Adams Maverick Software .

Twist, Touch & TravelTouch, Twist, and Travel

Harnessing the iPhone's Unique Features

Glenda AdamsMaverick Software

www.mavericksoftwaregames.com

Your Mission:Stand out among 22,000 games

Feel like an iPhone app!

Take advantage of the hardware

Unique control schemes

Don’t just port!

iPhone Hardware

Accelerometer

Multi-touch display

Location awareness

Compass (3GS only)

Accelerometer

Detect device orientation

Game input (steer, swing, balance)

Alternate input (shake, flip)

Accelerometer Interface

Provides X,Y,Z axis values

Updates via delegate callback, you set the frequency (up to 100 Hz)

Hardware is very sensitive, you must filter the data

Provide your own calibration

Accelerometer Setup:

- (void) setupAccelerometer

{

UIAccelerometer* accel = [UIAccelerometer sharedAccelerometer];

accel.updateInterval = 1.0f / kFrequency;

accel.delegate = self;

}

Delegate callback:(void)accelerometer:(UIAccelerometer*)accelerometer

didAccelerate:(UIAcceleration*)acceleration

{

// Get axis values

UIAccelerationValue x, y, z;

x = acceleration.x;

y = acceleration.y;

z = acceleration.z;

}

Simple low-pass filter to track gravity vector

static BOOL init = NO;static UIAccelerationValue xValue = 0.0,

yValue = 0.0, zValue = 0.0;

if(!init) { // Get the initial value

gravityX = acceleration.x;gravityY = acceleration.y;init = YES;

}else { // Modify the intial value with the current one

gravityX = (acceleration.x * 0.1) + (gravityX * 0.9);gravityY = (acceleration.y * 0.1) + (gravityY * 0.9);

}

** Not accurate enough for a game controller! **

Accelerometer Tips For tilt controls, calibrate a “home”

position at game start, pause/resume, start of a level, etc.

Delegate callbacks are not guaranteed exact timing.

View based orientation support:

- (BOOL) shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation

- (void) didRotateFromInterfaceOrientation: (UIInterfaceOrientation)fromInterfaceOrientation

Multi-touch display

Direct manipulation

Support multiple simultaneous touches

Gestures

Single touch sequence

Touch Began Touch Moved Touch Ended

Multi-touch sequence

Touch1 Began Touch1 Moved Touch2 Began

Touch2 Moved Touch2 Ended Touch1 Ended

UIResponder Touch-related Methods

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent*)event;- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent*)event;- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent*)event;- (void)touchesCancelled:(NSSet *)touches withEvent:

(UIEvent*)event;

UITouch properties

UITouchPhase phase;NSUInteger tapCount;NSTimeInterval timestamp;UIView* view;UIWindow* window;

Finding a touch location

UITouch* touch = [touches anyObject];CGPoint where = [touch locationInView:myView];

Touch tips No API for gesture support

Size of touch area is 44x44, design UI accordingly

UITouch objects live across calls to TouchesBegan, Moved, etc.

Make sure to handle TouchesCancelled!

Handle multiple touches for complex multi-button virtual controls

Location Awareness

Accessed via the Core Location framework

User can opt-out

All devices, not just GPS enabled.

GPS, <40 m

Wifi, <100 m

Cell Towers, 1km-3km

Data from Core Location

Latitude

Longitude

Altitude

Accuracy

Properties:BOOL locationServicesEnabled;

CLLocationAccuracy desiredAccuracy;

CLLocation * location;

Methods:- (void) startUpdatingLocation;

- (void) stopUpdatingLocation;

Delegate Methods:

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error

Core Location tips Limit time between

startUpdatingLocation and stopUpdatingLocation

Handle loss/denial of location services

GPS drains battery fast!

Compass

Currently only on iPhone 3GS

Same x,y,z axis as accelerometer

Magnetic north vs True north

Part of Core Location framework

Compass specific Core Location Properties:BOOL headingAvailable;

CLLocationDegrees headingFilter;

CLHeading propertiesCLLocationDirection magneticHeading;

CLLocationDirection trueHeading;

CLLocationDirection headingAccuracy;

CLHeadingComponentValue x,y,z;

Methods:- (void) startUpdatingHeading;

- (void) stopUpdatingHeading;

Delegate Methods:

- (void) locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading

Compass tips Interference

Recalibration

True north only available if location is known

Recap

Use hardware features to make your game feel natural on the iPhone

Look at Apple sample code

Think Different

Twist, Touch & TravelTouch, Twist, and Travel

Harnessing the iPhone's Unique Features

Glenda AdamsMaverick Software

[email protected]

Q&A