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Twist, Touch & Travel

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

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Twist, Touch & Travel

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

  2. 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!

  3. iPhone Hardware • Accelerometer • Multi-touch display • Location awareness • Compass (3GS only)

  4. Accelerometer • Detect device orientation • Game input (steer, swing, balance) • Alternate input (shake, flip)

  5. 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

  6. Accelerometer Setup: - (void) setupAccelerometer { UIAccelerometer* accel = [UIAccelerometersharedAccelerometer]; accel.updateInterval = 1.0f / kFrequency; accel.delegate = self; } Delegate callback: (void)accelerometer:(UIAccelerometer*)accelerometer didAccelerate:(UIAcceleration*)acceleration { // Get axis values UIAccelerationValuex, y, z; x = acceleration.x; y = acceleration.y; z = acceleration.z; }

  7. Simple low-pass filter to track gravity vector static BOOL init = NO; static UIAccelerationValuexValue = 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! **

  8. 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

  9. Multi-touch display • Direct manipulation • Support multiple simultaneous touches • Gestures

  10. Single touch sequence Touch Began Touch Moved Touch Ended

  11. Multi-touch sequence Touch1 Moved Touch2 Began Touch1 Began Touch2 Ended Touch1 Ended Touch2 Moved

  12. 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; NSUIntegertapCount; NSTimeInterval timestamp; UIView* view; UIWindow* window; Finding a touch location UITouch* touch = [touches anyObject]; CGPoint where = [touch locationInView:myView];

  13. 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

  14. 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

  15. Data from Core Location • Latitude • Longitude • Altitude • Accuracy

  16. Properties: BOOL locationServicesEnabled; CLLocationAccuracydesiredAccuracy; CLLocation * location; Methods: - (void) startUpdatingLocation; - (void) stopUpdatingLocation; Delegate Methods: - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocationfromLocation:(CLLocation *)oldLocation - (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error

  17. Core Location tips • Limit time between startUpdatingLocation and stopUpdatingLocation • Handle loss/denial of location services • GPS drains battery fast!

  18. Compass • Currently only on iPhone 3GS • Same x,y,z axis as accelerometer • Magnetic north vs True north • Part of Core Location framework

  19. Compass specific Core Location Properties: BOOL headingAvailable; CLLocationDegreesheadingFilter; CLHeading properties CLLocationDirectionmagneticHeading; CLLocationDirectiontrueHeading; CLLocationDirectionheadingAccuracy; CLHeadingComponentValuex,y,z; Methods: - (void) startUpdatingHeading; - (void) stopUpdatingHeading; Delegate Methods: - (void) locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading

  20. Compass tips • Interference • Recalibration • True north only available if location is known

  21. Recap • Use hardware features to make your game feel natural on the iPhone • Look at Apple sample code • Think Different

  22. Touch, Twist, and Travel Harnessing the iPhone's Unique Features Twist, Touch & Travel Q&A Glenda Adams Maverick Software glenda@mavericksoftwaregames.com

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