Sparrow Forum

1. 

   isicom
   Member

   Hi there,

   I am very new in sparrow framework and need help to rotate an object by touching with fingers on screen.
   What I tried to do was the using of geometry formula: cos phi = |ri *r2| /|r1|*|r2|

   Let's show:

   - (void)onTouch:(SPTouchEvent*)event
   {
   SPTouch *touch = [[event touchesWithTarget:self andPhase:SPTouchPhaseBegan] anyObject];
   if (touch)
   {
   SPPoint *touchPosition = [touch locationInSpace:self];
   NSLog(@"Touched position (%f, %f)",touchPosition.x, touchPosition.y);

   // calculate the new direction vector: Init of lastPosition: x=120, y=200
   CGPoint touchDirVector = CGPointMake(touchPosition.x-lastPosition.x, touchPosition.y-lastPosition.y);

   // geometry theory: cos phi = |ri *r2| /|r1|*|r2|
   float formularUP = (touchDirVector.x*lastDirVector.x)+(touchDirVector.y*lastDirVector.y);

   float formularDown = sqrt(pow(touchDirVector.x,2.0)+pow(touchDirVector.y,2.0)) *
   sqrt(pow(lastDirVector.x,2.0)+pow(lastDirVector.y,2.0));

   float cosPhi = acos(formularUP/formularDown);

   // Store the new direction vector
   lastDirVector =CGPointMake(touchDirVector.x, touchDirVector.y);

   [self.stage.juggler removeTweensWithTarget:sprite];

   // create a new juggler
   tween = [SPTween tweenWithTarget:sprite time:2.5f transition:SP_TRANSITION_EASE_IN];

   [tween animateProperty:@"rotation" targetValue:cosPhi]
   [self.stage.juggler addObject:tween];

   That's all. the object do not rotate correctly. It turns left although it have to turn right, and opposite.

   Have anybody an idea, where the error fits???

   Thank you.

   isicom

   Posted 1 year ago #
2. 

   ronaldmathies
   Moderator

   Do you want to do one or two finger rotation, i can make a sample of both ( since i implemented both versions )? Could be that my sollution is different but they do work.

   Posted 1 year ago #
3. 

   ronaldmathies
   Moderator

   - (void)onRotateTouchEvent:(SPTouchEvent*)_event {
   SPTouch *touchMoved = [[_event touchesWithTarget:[self sprite] andPhase:SPTouchPhaseMoved] anyObject];
   if (touchMoved) {
   SPPoint *previousPos1 = [[SPPoint alloc] initWithX:[[self sprite] x] y:[[self sprite] y]];
   SPPoint *currentPos1 = [[SPPoint alloc] initWithX:[[self sprite] x] y:[[self sprite] y]];

   SPPoint *previousPos2 = [touchMoved previousLocationInSpace:[[self sprite] parent]];
   SPPoint *currentPos2 = [touchMoved locationInSpace:[[self sprite] parent]];

   CGFloat currentAngle = angleBetweenLinesInRadians(previousPos1, previousPos2, currentPos1, currentPos2);
   [[self sprite] setRotation:[[self sprite] rotation] + currentAngle];
   }
   }

   static inline CGFloat angleBetweenLinesInRadians(SPPoint *line1Start, SPPoint *line1End, SPPoint *line2Start, SPPoint *line2End) {

   CGFloat a = line1End.x - line1Start.x;
   CGFloat b = line1End.y - line1Start.y;
   CGFloat c = line2End.x - line2Start.x;
   CGFloat d = line2End.y - line2Start.y;

   CGFloat line1Slope = (line1End.y - line1Start.y) / (line1End.x - line1Start.x);
   CGFloat line2Slope = (line2End.y - line2Start.y) / (line2End.x - line2Start.x);

   CGFloat degs = acosf(((a*c) + (b*d)) / ((sqrt(a*a + b*b)) * (sqrt(c*c + d*d))));

   return (line2Slope > line1Slope) ? degs : -degs;
   }

   Posted 1 year ago #
4. 

   isicom
   Member

   Thank you very much.

   The Idea is, there is a Helicopter from buttom view. It should turn in the direction of the new touched coordinate by one finger. Every time if there is a new touch, it should turn to there by using the shortest rotation direction.

   Posted 1 year ago #
5. 

   isicom
   Member

   Hey there,

   my problem is still there.

   Image there is an arrow fix positioned on x=120 y=200

   It should rotate in the touched direction. But it doesn't work:

   - (void)onTouch:(SPTouchEvent*)event
   {
   SPTouch *touch = [[event touchesWithTarget:self andPhase:SPTouchPhaseBegan] anyObject];
   if (touch)
   {
   SPPoint *touchPosition = [touch locationInSpace:self];

   // last positon is still fix: x=120 y=200
   CGPoint touchDirVector = CGPointMake(touchPosition.x-lastPosition.x, touchPosition.y-lastPosition.y);
   // the arrow show up... direction vector lastDirVector x=0, y=-1

   CGFloat counter = ( touchDirVector.x * lastDirVector.x ) + ( touchDirVector.y * lastDirVector.y );
   CGFloat base = sqrt( pow( touchDirVector.x, 2.0 ) + pow( touchDirVector.y, 2.0 )) *
   sqrt( pow( lastDirVector.x , 2.0 ) + pow( lastDirVector.y , 2.0 ));

   if (base ==0) return;

   CGFloat cosPhi = acosf(counter/base);

   // save the dir vector
   lastDirVector =CGPointMake(touchDirVector.x, touchDirVector.y);

   // create a new juggler
   tween = [SPTween tweenWithTarget:sprite time:2.5f transition:SP_TRANSITION_EASE_IN];

   // now rotate it
   [tween animateProperty:@"rotation" targetValue:cosPhi]

   //Register the tween at the nearest juggler.
   [self.stage.juggler addObject:tween];
   }

   Posted 1 year ago #
6. 

   isicom
   Member

   I got it:

   Important of rotation is not only the degrees, also important is the orientation of the rotation. Here the formula

   orientation = y1*x2 -x1*y2
   And now check if orientation < 0 then rotation is -rotation

   Do not forget to add the current rotation to the now calculated rotation object.rotation += rotation

   Posted 1 year ago #
7. 

   ronaldmathies
   Moderator

   Yes, the pieces in my code for these are:

   return (line2Slope > line1Slope) ? degs : -degs;

   and:

   [[self sprite] setRotation:[[self sprite] rotation] + currentAngle];

   Posted 1 year ago #
8. 

   isicom
   Member

   Exactly...sorry for my fooling. I had the problem, that I haven't
   - SPTouchePhaseMove
   - 2 Touch points

   The rethinking form your example to my situation was a little bit hard for me.

   My mind was, I have
   - one position of object
   - one current rotation
   - one touch point

   how I said, it WAS difficult...but I got it

   Thank you for your post. It helps me very much.

   isicom

   Posted 1 year ago #

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