SpriteKit - zRotaion with ratio - math

Question

I'm stuck trying to make a analog clock where the hour hand is following the minute hand.
Tried all i can think off but the ratio is off.
Dragging the minute hand works correctly so i think it's the way i calculate the ratio of which the hour hand should rotate.
This is my most recent try of many...
Code:
#define DEGREES_TO_RADIANS(angle) ((angle) / 180.0 * M_PI)
#define RADIANS_TO_DEGREES(radians) ((radians) * (180.0 / M_PI))
CGFloat oldAngleInRadians = M_PI_2;
- (void)rotateNode:(SKSpriteNode *)node forTouch:(UITouch *)touch
{
if ([node isEqual:dial]) return;
CGPoint positionInDial = [touch locationInNode:dial];
float deltaY = positionInDial.y - minuteIndicator.anchorPoint.y;
float deltaX = positionInDial.x - minuteIndicator.anchorPoint.x;
CGFloat angleInRadians = atan2f(deltaY, deltaX);
// Minute hand rotation in this case
[node runAction:[SKAction rotateToAngle:angleInRadians - (M_PI / 2) duration:0]];
if (self.difficulty == kMediumDifficulty ) {
[self updateHourhandAngleWithNewAngle:angleInRadians oldAngle:oldAngleInRadians];
oldAngleInRadians = angleInRadians;
}
}
#pragma mark - Rotate hour hand with minute hand
- (void)updateHourhandAngleWithNewAngle:(CGFloat)newAngle oldAngle:(CGFloat)oldAngle
{
double newAngleDeg = RADIANS_TO_DEGREES(newAngle);
double oldAngleDeg = RADIANS_TO_DEGREES(oldAngle);
double differenceDeg = 0;
if (newAngleDeg > 0 && oldAngleDeg < 0) {
differenceDeg = oldAngleDeg - ( - 1 * newAngleDeg );
} else if (newAngleDeg < 0 && oldAngleDeg > 0) {
differenceDeg = fabsf(newAngleDeg) - oldAngleDeg;
} else {
differenceDeg = newAngleDeg - oldAngleDeg;
}
[hourIndicator runAction:[SKAction rotateByAngle:DEGREES_TO_RADIANS((differenceDeg / 12.0f)) duration:0]];
}

Answer 1

Not sure if I understood your problem correctly, but this is how I would make an analog clock using SpriteKit:
// MyScene.m
- (void) didMoveToView:(SKView *)view
{
[self.clock didEnterScene];
}
- (void) update:(CFTimeInterval)currentTime
{
CGFloat dt = 0.0;
if (self.lastUpdateInterval > 0)
{
dt = currentTime - self.lastUpdateInterval;
}
[self.clock update:dt];
self.lastUpdateInterval = currentTime;
}
// ClockNode.m
- (void) didEnterScene
{
SKSpriteNode* secHand = [SKSpriteNode spriteNodeWithColor:[UIColor blueColor] size:CGSizeMake(2, 100)];
SKSpriteNode* minHand = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(5, 100)];
SKSpriteNode* hourHand = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(10, 70)];
secHand.position = CGPointMake(CGRectGetMidX(self.scene.frame), CGRectGetMidY(self.scene.frame));
minHand.position = secHand.position;
hourHand.position = secHand.position;
secHand.anchorPoint = CGPointMake(0.5, 1.0);
minHand.anchorPoint = CGPointMake(0.5, 1.0);
hourHand.anchorPoint = CGPointMake(0.5, 1.0);
[self addChild:secHand];
[self addChild:minHand];
[self addChild:hourHand];
_secHand = secHand;
_minHand = minHand;
_hourHand = hourHand;
_secHand.zRotation = M_PI;
_minHand.zRotation = M_PI;
_hourHand.zRotation = M_PI;
_msec = 0.0f;
_sec = 0.0f;
_min = 0.0f;
_hour = 0.0f;
}
- (void) update:(CGFloat)dt
{
_msec += dt;
if (_msec >= 1)
{
_msec -= 1;
_sec += 1;
_secHand.zRotation -= 2*M_PI / 60;
}
if (_sec >= 60)
{
_sec -= 60;
_min += 1;
_minHand.zRotation -= 2*M_PI / 60;
}
if (_min >= 60)
{
_min -= 60;
_hour += 1;
_hourHand.zRotation -= 2*M_PI / 12;
}
if (_hour >= 12)
{
_hour -= 12;
}
}