I have a gesture recignizer, and I need to rotate a body:
- (void) rotate:(UIGestureRecognizer*)recognizer node:(CCNode*)node
{
b2Body *body = (b2Body*)[node.parent userData];
UIRotationGestureRecognizer* rotate = (UIRotationGestureRecognizer*)recognizer;
b2Vec2 pos = body->GetPosition();
body->SetTransform(pos, (- rotate.rotation));
}
offcorse, when I starting rotation, it starts from zero angle. *But how to continue rotation from current angle? * I cant just add rotate.rotation to tu current angle: this method called on every move, and angle is calculated from very begining of gesture. keep track on actual current angle (without anctive gesture's angle), will be a pretty hard task, I think
I found solution:
I checked state of gesture (there is a begining state):
- (void) rotate:(UIGestureRecognizer*)recognizer node:(CCNode*)node
{
b2Body *body = (b2Body*)[node.parent userData];
UIRotationGestureRecognizer* rotate = (UIRotationGestureRecognizer*)recognizer;
if (rotate.state == UIGestureRecognizerStateBegan)
{
baseAngle = body->GetAngle();
}
b2Vec2 pos = body->GetPosition();
body->SetTransform(pos, (baseAngle - rotate.rotation));
}
Related
I added a -(void) detectTouch: (UIPanGestureRecognizer *) event for UIScrollView and detecting the angle on which user is moving his finger. My task is to scroll the UIScrollView horizontally only when user is moving the finger between 0 - 30 degrees (just to make sure he is drawing a horizontal straight line) otherwise I have to disable the UIScrollView scroll.
I am detecting the angle by drawing a triangle using the touch starting point and ending point.
Problem: I enabled the UIScrollView scroll when the angle is < 30 degrees but this is not working on the first time. Although I enabled scroll using scrollEnabled = YES it is working only when user is stopped touching the screen (taking the finger from the screen).
The following code I used to
- (void)viewDidLoad
{
[super viewDidLoad];
[self PanGesture:self.view callBack:#selector(detectTouch:) delegate:self];
incrementer = 0;
}
-(void) detectTouch: (UIPanGestureRecognizer *) event{
// Calculating point A on gesture starts
if(event.state == UIGestureRecognizerStateBegan){
pointA.x = fabs([event translationInView:event.view].x);
pointA.y = fabs([event translationInView:event.view].y);
NSLog(#"A: %f, %f", pointA.x, pointA.y);
}
incrementer += 1;
// Start calculating Point B, Point C on calling this function 3 times
if(incrementer >= 3){
// Calculating point C
pointC.x = fabs([event translationInView:event.view].x);
pointC.y = fabs([event translationInView:event.view].y);
NSLog(#"C: %f, %f", pointC.x, pointC.y);
// calculate pointB using A, C
pointB.x = fabs(pointC.x);
pointB.y = fabs(pointA.y);
NSLog(#"B: %f, %f", pointB.x, pointB.y);
float X = pointB.x - pointA.x;
float Y = pointC.y - pointB.y;
float angle = (atan(fabs(Y) / fabs(X)) * 180 / M_PI);
if(angle > 30){
// This disable is not working on while user is moving the finger
self.myScrollView.scrollEnabled = NO;
NSLog(#"UIScroll Disabled");
}else{
// This enable is not working on while user is moving the finger
self.myScrollView.scrollEnabled = YES;
NSLog(#"UIScroll Enabled");
}
incrementer = 0;
}
}
How can I enable UIScrollView scroll while user is moving the touch?
Since UIScrollView seems to accept scrolling only with a new touch after you set .scrollEnabled to YES, I would do the following:
set .scrollEnabled to NO
Track the touch (e. g. with touchesMoved::)
check whether you 30 degrees condition is met
use the movement to adjust UIScrollView.contentOffset
is there anyway we can do rotation of image in a pendulum effect in iphone using UIView Animation or CoreAnimation
Use CGAffineTransformRotate to rotate your UIImageView e.g.
yourImage.transform = CGAffineTransformRotate(CGAffineTransformIdentity, M_PI * (_angle/ 180.0));
Also, you'll need to set up the anchor point on your image, prior to rotating it, so that you can make it swing from the correct position. e.g.
yourImage.layer.anchorPoint = CGPointMake(0.5,0); // Set anchor to top middle.
Obviously, you'll need to set up a timer to adjust move the image and control the angle. You could do something like the following in a timer. (untested)
_angle = 45; // Set starting angle.
_direction = 1; // Set starting direction.
-(void) movePend
{
if(_direction == 45){
_direction = 1;
} else if(_direction == 180) {
_direction = 0;
}
_angle = (_direction) ? _angle-- : _angle++; // Determine which way to rotate.
yourImage.transform = CGAffineTransformRotate(CGAffineTransformIdentity, M_PI * (_angle/ 180.0));
}
i use following code to move my Box2D object into screen, but because gravity of my world or something else i dont know why my objects is forced to move down, i am new to box2d.
i want to move my object in entire world without gravity.
-(void) tick:(NSTimer *)timer {
int32 velocityIterations = 8;
int32 positionIterations = 1;
world->Step(1.0f/60.0f, velocityIterations, positionIterations);
for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
{
if (b->GetUserData() != NULL)
{
UIView *oneView = (UIView *)b->GetUserData();
CGPoint newCenter = CGPointMake(b->GetPosition().x * PTM_RATIO,self.view.bounds.size.height - b->GetPosition().y * PTM_RATIO);
oneView.center = newCenter;
CGAffineTransform transform = CGAffineTransformMakeRotation(- b->GetAngle());
oneView.transform = transform;
}
}
}
my accelerometer code is as follow.
- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
b2Vec2 gravity;
gravity.Set( acceleration.x * 1.81, acceleration.y * 1.81 );
world->SetGravity(gravity);
}
pleas if any one work around.
Thanks.
As i understand you want to move your object setting it's position. It's a bad idea because it will provide non-physical behavior of the bodies colliding with your object. That's because if you will only change the position of your body it's velocity for physics engine will be still zero and collision will be processed according to zero speed of your object.
A better solution is to use b2_kinematicBody type for your object. Then you will be able to control it's motion specifying it's velocity vector and physics will behave as expected. Also the gravity (and no other forces) will not be applied to your object because of it's type.
EDIT
//creation
b2BodyDef bDef;
bDef.type = b2_kinematicBody;
bDef.position.Set(5, 6);
b2Body *body = physWorld->CreateBody(&bDef);
//control
body->SetLinearVelocity(b2Vec2(3, 4));
I have a need to tap and drag a UIView on the screen with deceleration. I have written the code very nicely for moving the view with touches, but need the object to keep moving with a certain degree of inertia (once a certain acceleration threshold is met), decelerating until it stops, or meets the boundary of the screen. This is not for a game, but using some standard UIView controls. The biggest part I am grappling with is the acceleration.
Any good algorithms that you have written to accomplish the same?
Edit:
I am using an animation block on the touchesEnded: method, but there is a noticeable delay between the time that a person lets go of their finger and the animation kicks in:
[UIView transitionWithView:self
duration:UI_USER_INTERFACE_IDIOM() ==
UIUserInterfaceIdiomPhone ? 0.33f : 0.33f * 2.0f
options:UIViewAnimationCurveEaseOut
animations:^(void){
if (dir == 1) // Flicked left
{
self.center = CGPointMake(self.frame.size.width * 0.5f,
self.center.y);
}
else { // Flicked right
self.center = CGPointMake(
self.superview.bounds.size.width -
(self.frame.size.width * 0.5f), self.center.y);
}
}
completion:^(BOOL finished){
// Do nothing
}];
The problem is in the timing function used for the animation. The animation should be as fast as the user's dragging in the first, and quickly decelerates. The following code shows a very simple example of implementing this behavior.
First, in my touchesBegan:withEvent: method, I recorded the first touch location to my point buffer. I'm buffering two touch locations to get the movement vector of the view, and there could be different ways of getting the vector.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
ivar_lastPoint[0] = [[touches anyObject] locationInView:self];
ivar_lastPoint[1] = ivar_lastPoint[0];
ivar_touchOffset.x = ivar_lastPoint[0].x - self.sprite.position.x;
ivar_touchOffset.y = ivar_lastPoint[0].y - self.sprite.position.y;
self.lastTime = [NSDate date];
}
Then, in touchesMoved:withEvent: method, I updated the location of the view. Actually, I used a CALayer rather than a view, as I want to use a custom timing function for its animation. So, I update the location of the layer according to the user, and for a given interval, I update the location buffers.
#define kSampleInterval 0.02f
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
[CATransaction begin];
[CATransaction setDisableActions:YES];
/* First of all, move the object */
CGPoint currentPoint = [[touches anyObject] locationInView:self];
CGPoint center = self.sprite.position;
center.x = currentPoint.x - ivar_touchOffset.x;
center.y = currentPoint.y - ivar_touchOffset.y;
self.sprite.position = center;
/* Sample locations */
NSDate *currentTime = [NSDate date];
NSTimeInterval interval = [currentTime timeIntervalSinceDate:self.lastTime];
if (interval > kSampleInterval) {
ivar_lastPoint[0] = ivar_lastPoint[1];
ivar_lastPoint[1] = currentPoint;
self.lastTime = currentTime;
self.lastInterval = interval;
}
[CATransaction commit];
}
self.sprite is a reference to the CALayer object on my view. I don't need animation for dragging so I disabled it by using CATransaction class object.
Finally, I calculate the vector and apply the animation in touchesEnded:withEvent: method. Here, I created a custom CAMediaTimingFunction, so it's really "fast-in, ease-out".
#define kDecelerationDuration 1.0f
#define kDamping 5.0f
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint targetPoint;
NSDate *currentTime = [NSDate date];
NSTimeInterval interval = self.lastInterval + [currentTime timeIntervalSinceDate:self.lastTime];
targetPoint.x = self.sprite.position.x + (ivar_lastPoint[1].x - ivar_lastPoint[0].x)/interval*kDecelerationDuration/kDamping;
targetPoint.y = self.sprite.position.y + (ivar_lastPoint[1].y - ivar_lastPoint[0].y)/interval*kDecelerationDuration/kDamping;
if (targetPoint.x < 0) {
targetPoint.x = 0;
} else if (targetPoint.x > self.bounds.size.width) {
targetPoint.x = self.bounds.size.width;
}
if (targetPoint.y < 0) {
targetPoint.y = 0;
} else if (targetPoint.y > self.bounds.size.height) {
targetPoint.y = self.bounds.size.height;
}
CAMediaTimingFunction *timingFunction = [CAMediaTimingFunction functionWithControlPoints:
0.1f : 0.9f :0.2f :1.0f];
[CATransaction begin];
[CATransaction setValue:[NSNumber numberWithFloat:kDecelerationDuration] forKey:kCATransactionAnimationDuration];
[CATransaction setAnimationTimingFunction:timingFunction];
self.sprite.position = targetPoint;
[CATransaction commit];
}
This is a very simple example. You may want a better vector-getting mechanism. Also, this only move a visual component (CALayer). You would probably need an UIView object to handle events from the object. In this case, you might want to animate through CALayer, and move the actual UIView object separately. There could be multiple ways of handling the CALayer animation and UIView relocation together.
Use Core Animation. It's pretty straightforward if you look at the docs for UIView -- create an animation that sets the final position of the view, and specify UIViewAnimationOptionCurveEaseOut as the timing curve. The whole thing will take you just a handful of lines to implement.
You can use a constant acceleration for the object to stop moving at a constant rate of slow down. Or you can make the acceleration increase or decrease depending on if you want the deceleration to be quicker/slower towards the point of reaching zero velocity.
struct Velocity {
float x;
float y; }
Vector acceleration = your acceleration equation. // can be constant
Vector newVelocity = oldVelocity + acceleration * timeDelta;
Vector newPosition = newVelocity * timeDelta;
assuming you have a normalized vector for your direction of travel, and you are just countering that direction you can use float instead of Vector.
You have to bound the newPosition on the border. And you have to stop iterating per time delta when velocity becomes negative.
I want to rotate the image around its center point.The problem i am facing is i need to get the angle to calculate in touch moved event (i dont want to use multi touch).I am current using the below code
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
NSArray *allTouches = [touches allObjects];
gestureStartPoint = gestureMovedPoint;//i am getting the gestureStartPoint on touch began event
gestureMovedPoint = [[allTouches objectAtIndex:0] locationInView:[self superview]];
NSLog(#"gestureMovedPoint = %#",NSStringFromCGPoint(gestureMovedPoint));
}
CGFloat previousAngle = [self angleBetweenPoints:gestureStartPoint second11:gestureMovedPoint]; // atan2(gestureMovedPoint.y - gestureStartPoint.y, gestureMovedPoint.x - gestureStartPoint.x) * 180 / M_PI;
CGFloat currentAngle =atan2(self.transform.b, self.transform.a);//atan2(gestureMovedPoint.y - gestureStartPoint.y,gestureMovedPoint.x - gestureStartPoint.x) * 180 / M_PI;
CGFloat angleToRotate = currentAngle - previousAngle;
float xpoint = (((atan2((gestureMovedPoint.x - gestureStartPoint.x) , (gestureMovedPoint.y - gestureStartPoint.y)))*180)/M_PI);
CGAffineTransform transform = CGAffineTransformMakeRotation(angleToRotate-100);
self.transform = transform;
Kindly help me find the solution as i am stuck here and need to complete this application very soon as there is a dead line.
Thanks in advance
Glad I remember triginometry
-(void)degreesToRotateObjectWithPosition:(CGPoint)objPos andTouchPoint:(CGPoint)touchPoint{
float dX = touchPoint.x-objPos.x; // distance along X
float dY = touchPoint.y-objPos.y; // distance along Y
float radians = atan2(dY, dX); // tan = opp / adj
//Now we have to convert radians to degrees:
float degrees = radians*M_PI/360;
return degrees;
}
Once you have your nice method, just do this in the touch event method. (I forgot what it's called...)
CGAffineTransform current = view.transform;
[view setTransform:CGAffineTransformRotate(current, [self degreesTorotateObjectWithPosition:view.frame.origin andTouchPoint:[touch locationInView:parentView]]
//Note: parentView = The view that your object to rotate is sitting in.
This is pretty much all the code that you'll need.The math is right, but I'm not sure about the setTransform stuff. I'm at school writing this in a browser. You should be able to figure it out from here.
Good luck,
Aurum Aquila
Have to think at this. But I will prefer rotating the view with two touches. It will be much simpler.
I did struggle a bit with how to get a touch driven rotation, even more so because I want 100% understanding of the code I am using. So I ended up, after many failed attempts, with this:
- (CGFloat) pointToAngleFromCenter: (CGPoint) point {
// transform point to a self.center'ed origin based coordinate system
point.x = point.x - self.center.x ;
// ditto for y, but compensate for y going downwards to y going upwards
point.y = self.center.y - point.y ;
return ::atan2(point.y, point.x) ;
}
If anyone has a better name for this method, I'm all ears.
What it does is that it takes a point in parent view coordinates, remaps it relative to the center of the view (which is in parent view coordinate), and computes the angle between this remapped point and the axis [0X]. To do so, it normalizes y to the normal mathematical coordinates (y goes up when its value increases, not down), hence self.center.y - point.y and not the opposite.
Finally, in touchesMoved:
- (void) touchesMoved: (NSSet *) touches withEvent: (UIEvent *) event {
UITouch * touch = [touches anyObject] ;
CGFloat currA = [self pointToAngleFromCenter:[touch locationInView:self.superview]] ;
CGFloat prevA = [self pointToAngleFromCenter:[touch previousLocationInView:self.superview]] ;
// the current value of the rotation angle
CGFloat tranA = ::atan2(self.transform.b, self.transform.a) ;
// the angle difference between last touch and the current touch
CGFloat diffA = currA - prevA ;
// the new angle resulting from applying the difference
CGFloat angle = tranA - diffA ;
CGAffineTransform t = ::CGAffineTransformMakeRotation(angle) ;
self.transform = t ;
[self setNeedsDisplay] ;
}