I'm trying to make my first game using Spritekit, so i have a sprite that i need to move around using my accelerometer. Well, no problem doing that; movement are really smooth and responsive, the problem is that when i try to rotate my sprite in order to get it facing its own movement often i got it "shaking" like he has parkinson. (:D)
i did realize that this happens when accelerometer data are too close to 0 on one of x, y axes.
So the question: Is there a fix for my pet parkinson?? :D
Here is some code:
-(void) update:(NSTimeInterval)currentTime{
static CGPoint oldVelocity;
//static CGFloat oldAngle;
if(_lastUpdatedTime) {
_dt = currentTime - _lastUpdatedTime;
} else {
_dt = 0;
}
_lastUpdatedTime = currentTime;
CGFloat updatedAccelX = self.motionManager.accelerometerData.acceleration.y;
CGFloat updatedAccelY = -self.motionManager.accelerometerData.acceleration.x+sinf(M_PI/4.0);
CGFloat angle = vectorAngle(CGPointMake(updatedAccelX, updatedAccelY));
_velocity = cartesianFromPolarCoordinate(MAX_MOVE_PER_SEC, angle);
if(oldVelocity.x != _velocity.x || oldVelocity.y != _velocity.y){
_sprite.physicsBody.velocity = CGVectorMake(0, 0);
[_sprite.physicsBody applyImpulse:CGVectorMake(_velocity.x*_sprite.physicsBody.mass, _velocity.y*_sprite.physicsBody.mass)];
_sprite.zRotation = vectorAngle(_velocity);
oldVelocity = _velocity;
}
}
static inline CGFloat vectorAngle(CGPoint v){
return atan2f(v.y, v.x);
}
i did try to launch the update of the _velocity vector only when updatedAccelX or updatedAccelY are, in absolute value >= of some values, but the result was that i got the movement not smooth, when changing direction if the value is between 0.1 and 0.2, and the problem wasn't disappearing when the value was under 0.1.
i would like to maintain direction responsive, but i also would like to fix this "shake" of the sprite rotation.
I'm sorry for my bad english, and thanks in advance for any advice.
You can try a low pass filter (cf. to isolate effect of gravity) or high pass filter (to isolate effects of user acceleration).
#define filteringFactor 0.1
- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
//low pass
accelerX = (acceleration.x * filteringFactor) + (accelerX * (1.0 - filteringFactor));
//idem … accelerY
//idem … accelerZ
//or high pass
accelerX = acceleration.x - ( (acceleration.x * filteringFactor) + (accelerX * (1.0 - filteringFactor)) );
//idem … accelerY
//idem … accelerZ
}
Related
I am making a game using Cocos2D and Kobold2D. In my game, I have a ship that I want to move to where the player taps, using this code:
KKInput * input = [KKInput sharedInput];
CGPoint tap = [input locationOfAnyTouchInPhase:KKTouchPhaseBegan];
if (tap.x != 0 && tap.y != 0)
{
[ship stopAllActions]; // Nullifies previous actions
int addedx = tap.x - ship.position.x;
int addedy = tap.y - ship.position.y;
int squaredx = pow(addedx, 2);
int squaredy = pow(addedy, 2);
int addedSquares = squaredx + squaredy;
int distance = pow(addedSquares, 0.5);
[ship runAction: [CCMoveTo actionWithDuration:distance/100 position:tap]];//makes ship move at a constant speed
}
The ship generally moves as I expect it to. However, if I tap near the ship, instead of smoothly moving to the tap location, it jumps to that location. How do I fix this?
Your logic is right but your calculation is lack precision.
Especially when you calc the fly time as distance/100. That means when distance < 100 the result is 0, so the ship is jumping to the destination.
Basically, you should use float instead of int when dealing with positions in cocos2d. And there are couple functions can do the work nicely.
You may change your code to this:
[ship stopAllActions]; // Nullifies previous actions
float distance = ccpDistance(tap, ship.position);
[ship runAction: [CCMoveTo actionWithDuration:distance/100.0f position:tap]];
First of All you can use the ccpDistance function of cocos2d to calculate distance between two point.
And it jumps because if u tap too near the distance is too small suppose 2 or 10 ... the you are dividing it on 100
e.g 5/100 = 0.05 which is too low that's why it jumps.
You need to handle it manually i think some thing like if(speed<1) speed++; adding 1 to speed. shortcut solution :)
I'm writing a 2D ball game with sprite kit on iOS 7 and currently struggling on one physic simulation.
To explain the expected behavior: if a ball is dropped into a tea cup, it will circle around, loosing speed and finally stand still in the center of the cup.
I've tried to archive this with gravity, but gravity in sprite kit only applies to vertical X and Y axis, not Z-axis. I also tried to use level gravity by switching gravity values with small physic bodies on beginContact depending on the current ball position in the tea cup. But some contacts are dropped and the result is far away to look realistic.
I think I need to solve this in the update: method, but I have no idea which way to go.
Any advice greatly welcome and I need to mention that I'm not an expert on math, please explain your path to go. :-)
Since there's no built-in support for this kind of behavior in SpriteKit, rather than trying to hack existing functions to get what you want, you're probably better off integrating some published 2D physics formulas in your x,y 2D world. I would think that something like simulating magnetic or a homing behavior might be right for this.
A simple example would be something like (in the scene's -update: method):
CGFloat strength = 0.5; //(some scaling value)
CGPoint ballLocation = ball.position;
CGPoint cupLocation = cup.position;
[ball.physicsBody applyForce:CGVectorMake((cupLocation.x - ballLocation.x) * strength,
(cupLocation.y - ballLocation.y) * strength)];
following Joshd great idea, I have created an NSArray with like explained in my comment above. Hope this snippets does help some others...
The result could be found on youtube: http://youtu.be/Uephg94UH30
Sorry for the bad Airplay frame rate, it runs perfectly smooth on my iPad
The -update: functions does the work but only triggered if _meditationIsActive. This bool is set in -didBeginContact: when any ball gets in contact with a hole.
if (_lastCheck > 0.005)
{
if (_meditationIsActive)
{
CGFloat strength = 0.1; //(some scaling value)
CGPoint ballLocation;
CGPoint holeLocation;
for (MeditationHole * holeObj in _meditationHoles)
{
if (holeObj.connectedMeditationBall != nil)
{
ballLocation = holeObj.connectedMeditationBall.position;
holeLocation = holeObj.position;
[holeObj.connectedMeditationBall.physicsBody applyForce:CGVectorMake(
(holeLocation.x - ballLocation.x) * strength, (holeLocation.y - ballLocation.y) * strength)];
}
}
_meditationIsActive = [self doesMeditationApplies];
}
_lastCheck = 0;
}
At the end I'm checking if there is a valid ball out of the array in contact with a hole to avoid checking during every update. This is done with the following function where position check +/- 48 detects a ball close to a hole and +/-1 ball stands still
- (bool)doesMeditationApplies
{
bool isInArea = NO;
int perfectMatchCount = 0;
for (MeditationHole * holeObj in _meditationHoles)
{
if (holeObj)
{
if (holeObj.connectedMeditationBall != nil)
{
MeditationBall * ballObj = holeObj.connectedMeditationBall;
if ((ballObj.position.x >= holeObj.position.x - 48) &&
(ballObj.position.x <= holeObj.position.x + 48) &&
(ballObj.position.y >= holeObj.position.y - 48) &&
(ballObj.position.y <= holeObj.position.y + 48))
{
isInArea = YES;
}
else
{
holeObj.connectedMeditationBall = nil;
}
if ((ballObj.position.x >= holeObj.position.x - 1) &&
(ballObj.position.x <= holeObj.position.x + 1) &&
(ballObj.position.y >= holeObj.position.y - 1) &&
(ballObj.position.y <= holeObj.position.y + 1))
{
perfectMatchCount++;
isInArea = YES;
}
}
}
}
if (perfectMatchCount == _oxydStonesMax)
{
if (_sound)
{
self.pauseMusicPlaybackBlock(YES);
NSLog(#"PlaySound Meditation");
[OxydScene PlaySystemSound:#"Win2"];
}
isInArea = NO;
[self showPauseScreenWithWin:YES andPauseOnly:NO];
}
return isInArea;
}
Im using a technique to control a sprite by rotating left/right and then accelerating forward. I have 2 questions regarding it. (The code it pasted together from different classes due to polymorphism. If it doesn't make sense, let me know. The movement works well and the off screen detection as well.)
When player moves off screen i call the Bounce method. I want the player not to be able to move off screen but to change direction and go back. This works on top and bottom but left and right edge very seldom. Mostly it does a wierd bounce and leaves the screen.
I would like to modify the accelerate algorithm so that i can set a max speed AND a acceleration speed. Atm the TangentalVelocity does both.
float TangentalVelocity = 8f;
//Called when up arrow is down
private void Accelerate()
{
Velocity.X = (float)Math.Cos(Rotation) * TangentalVelocity;
Velocity.Y = (float)Math.Sin(Rotation) * TangentalVelocity;
}
//Called once per update
private void Deccelerate()
{
Velocity.X = Velocity.X -= Friction * Velocity.X;
Velocity.Y = Velocity.Y -= Friction * Velocity.Y;
}
// Called when player hits screen edge
private void Bounce()
{
Rotation = Rotation * -1;
Velocity = Velocity * -1;
SoundManager.Vulture.Play();
}
//screen edge detection
public void CheckForOutOfScreen()
{
//Check if ABOVE screen
if (Position.Y - Origin.Y / 2 < GameEngine.Viewport.Y) { OnExitScreen(); }
else
//Check if BELOW screen
if (Position.Y + Origin.Y / 2 > GameEngine.Viewport.Height) { OnExitScreen(); }
else
//Check if RIGHT of screen
if (this.Position.X + Origin.X / 2 > GameEngine.Viewport.Width) { OnExitScreen(); }
else
//Check if LEFT of screen
if (this.Position.X - Origin.X / 2 < GameEngine.Viewport.X) { OnExitScreen(); }
else
{
if (OnScreen == false)
OnScreen = true;
}
}
virtual public void OnExitScreen()
{
OnScreen = false;
Bounce();
}
Let's see if I understood correctly. First, you rotate your sprite. After that, you accelerate it forward. In that case:
// Called when player hits screen edge
private void Bounce()
{
Rotation = Rotation * -1;
Velocity = Velocity * -1; //I THINK THIS IS THE PROBLEM
SoundManager.Vulture.Play();
}
Let's suposse your sprite has no rotation when it looks up. In that case, if it's looking right it has rotated 90º, and its speed is v = (x, 0), with x > 0. When it goes out of the screen, its rotation becomes -90º and the speed v = (-x, 0). BUT you're pressing the up key and Accelerate method is called so immediately the speed becomes v = (x, 0) again. The sprite goes out of the screen again, changes its velocity to v = (-x, 0), etc. That produces the weird bounce.
I would try doing this:
private void Bounce()
{
Rotation = Rotation * -1;
SoundManager.Vulture.Play();
}
and check if it works also up and bottom. I think it will work. If not, use two different Bounce methods, one for top/bottom and another one for left/right.
Your second question... It's a bit difficult. In Physics, things reach a max speed because air friction force (or another force) is speed-dependent. So if you increase your speed, the force also increases... at the end, that force will balance the other and the speed will be constant. I think the best way to simulate a terminal speed is using this concept. If you want to read more about terminal velocity, take a look on Wikipedia: http://en.wikipedia.org/wiki/Terminal_velocity
private void Accelerate()
{
Acceleration.X = Math.abs(MotorForce - airFriction.X);
Acceleration.Y = Math.abs(MotorForce - airFriction.Y);
if (Acceleration.X < 0)
{
Acceleration.X = 0;
}
if (Acceleration.Y < 0)
{
Acceleration.Y = 0;
}
Velocity.X += (float)Math.Cos(Rotation) * Acceleration.X
Velocity.Y += (float)Math.Sin(Rotation) * Acceleration.Y
airFriction.X = Math.abs(airFrictionConstant * Velocity.X);
airFriction.Y = Math.abs(airFrictionConstant * Velocity.Y);
}
First, we calculate the accelartion using a "MotorForce" and the air friction. The MotorForce is the force we make to move our sprite. The air friction always tries to "eliminate" the movement, so is always postive. We finally take absolute values because the rotation give us the direction of the vector. If the acceleration is lower than 0, that means that the air friction is greater than our MotorForce. It's a friction, so it can't do that: if acceleration < 0, we make it 0 -the air force reached our motor force and the speed becomes constant.
After that, the velocity will increase using the acceleration. Finally, we update the air friction value.
One thing more: you may update also the value of airFriction in the Deccelarate method, even if you don't consider it in that method.
If you have any problem with this, or you don't understand something (sometimes my English is not very good ^^"), say it =)
I've tried following the example on XNA Development website but when the character jumps, they cant be controlled/cant stop the jump movement until its completed.
How do I get around that? Here is my jump code
private void Jump()
{
if (mCurrentState != FoxState.Jumping)
{
mCurrentState = FoxState.Jumping;
mStartingPosition = Position;
Direction.Y = Fox_vSpeed;
Speed = new Vector2(Fox_Speed, Fox_Speed);
}
}
Gravity is simply a force that affects the acceleration of an object. Acceleration changes the velocity of an object so you can do just that: Speed -= Vector2.UnitY * -2; You can then check collision with an object on the ground and once such collision happens you can zero the Y component of Speed (and possibly incur damage on the poor fox if the Y component is too high in magnitude (absolute value)).
Something like:
Update(GameTime gt)
{
if(mCurrentState == FoxState.Jumping)
{
Speed -= Vector2.UnitY * -2;
Position += Speed;
if(Position.Y > GroundLevel)
{
Position.Y = 0;
mCurrentState = FoxState.Walking;
}
}
}
Modify your question with details if you need more information.
I'm trying to code a very basic panorama app.
By using CMMotionManager I get motion updates to determine the appropriate moment to take the next picture. Sometimes this code works perfectly well, but in most cases it takes a photo too early or too late. Please help me understand what exactly I'm doing wrong.
Here is an example of code for an iPhone in its portrait mode.
#define CC_RADIANS_TO_DEGREES(__ANGLE__) ((__ANGLE__) * 57.29577951f) // PI * 180
#define FOV_IN_PORTRAIT_MODE 41.5;
double prevTime;
double currAngle;
- (void)motionUpdate:(CMDeviceMotion *)motion
{
if (!prevTime) {
prevTime = motion.timestamp;
return;
}
//Calculate delta time between previous motionUpdate call and _now_
double deltaTime = motion.timestamp - prevTime;
prevTime = motion.timestamp;
//Y axis rotation
CMRotationRate rotationRate = motion.rotationRate;
double rotation = rotationRate.y;
if (fabs(rotation) < 0.05) //igonre bias
return;
//Calculate the angular distance
double anglePathRad = rotation * deltaTime;
//calculate total panoram angle
currAngle += CC_RADIANS_TO_DEGREES(anglePathRad);
if (fabs(currAngle) >= FOV_IN_PORTRAIT_MODE) {
currAngle = 0;
[self takePicture];
}
}