How to rotate and point to cursor location in SpriteKit? - iphone

Question

I am working with the SpriteKit's Spaceship Demo and I want it to rotate to the location of where I click on the screen and then move toward it.
The current code I have only makes it move up the screen starting at position 50,50:
sprite.position = CGPointMake(50,50);
SKAction *fly = [SKAction moveByX:0.0F y:50.0F duration:1];
[sprite runAction:[SKAction repeatActionForever:fly];
How would I make it work?

Answer 1

So long answer, this will help you.(I benefited from raywenderlich's book)
//Math Utilities
static inline CGPoint CGPointSubtract(const CGPoint a,
const CGPoint b)
{
return CGPointMake(a.x - b.x, a.y - b.y);
}
static inline CGPoint CGPointMultiplyScalar(const CGPoint a,
const CGFloat b)
{
return CGPointMake(a.x * b, a.y * b);
}
static inline CGFloat CGPointLength(const CGPoint a)
{
return sqrtf(a.x * a.x + a.y * a.y);
}
static inline CGPoint CGPointNormalize(const CGPoint a)
{
CGFloat length = CGPointLength(a);
return CGPointMake(a.x / length, a.y / length);
}
static inline CGPoint CGPointAdd(const CGPoint a,
const CGPoint b)
{
return CGPointMake(a.x + b.x, a.y + b.y);
}
static const float SHIP_SPEED = 60.0;
#implementation yourScene
{
SKSpriteNode *ship;
NSTimeInterval _lastUpdateTime;
NSTimeInterval _dt;
CGPoint _velocity;
CGPoint _lastTouchLocation;
}
-(void)didMoveToView:(SKView *)view
{
ship = [SKSpriteNode spriteNodeWithImageNamed:#"Spaceship"];
ship.position = CGPointMake(50, 50);
[self addChild:ship];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint touchLocation = [touch locationInNode:self.scene];
[self moveShipToward:touchLocation];//Move Toward
}
-(void)update:(CFTimeInterval)currentTime {
/* Called before each frame is rendered */
{
if (_lastUpdateTime) {
_dt = currentTime - _lastUpdateTime;
} else {
_dt = 0;
}
_lastUpdateTime = currentTime;
CGPoint offset = CGPointSubtract(_lastTouchLocation, ship.position);
float distance = CGPointLength(offset);
if (distance < SHIP_SPEED * _dt) {
ship.position = _lastTouchLocation;
_velocity = CGPointZero;
} else {
[self moveSprite:ship velocity:_velocity];
[self rotateSprite:ship toFace:_velocity];
}
}
}
- (void)moveShipToward:(CGPoint)location
{
_lastTouchLocation = location;
CGPoint offset = CGPointSubtract(location, ship.position);
CGPoint direction = CGPointNormalize(offset);
_velocity = CGPointMultiplyScalar(direction, SHIP_SPEED);
}
- (void)moveSprite:(SKSpriteNode *)sprite
velocity:(CGPoint)velocity
{
CGPoint amountToMove = CGPointMultiplyScalar(velocity, _dt);
sprite.position = CGPointAdd(sprite.position, amountToMove);
}
- (void)rotateSprite:(SKSpriteNode *)sprite
toFace:(CGPoint)direction
{
sprite.zRotation = atan2f(direction.y, direction.x);
}