Touch and sprite rotation Problem.

cocos2d for iPhone » Programming » cocos2d support (graphics engine)

Touch and sprite rotation Problem.

(7 posts) (3 voices)

Started 1 year ago by paullstanley
Latest reply from SimzStudios

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paullstanley
Member

I am extremely new to programing and I apologize in advance for any inconvenience my ignorance may cause someone. Also thank you in advance. I have a sprite that represents the bullet holster on a revolver, The effect I am looking to accomplish is to have touch effect the rotation of the holster. I have all of the trig figured out and am almost accomplishing the desired result. Upon the very first instance of ccTouchMoved the bullet holster jumps to conform its rotation to the touch, almost like there is a point on the holster that is synched with the touch. After that it spins like you would expect. How do I get it to rotate relative to where I left off on my last touch?`
#import "MainScene.h"

@implementation MainScene

+(id) scene
{
CCScene *scene = [CCScene node];
MainScene *layer = [MainScene node];
[scene addChild: layer];

return scene;
}

-(id) init
{
if ((self=[super init])) {

CGSize size = [[CCDirector sharedDirector] winSize];

dial = [CCSprite spriteWithFile:@"dial.png"];
dial.position = ccp(size.width/2, dial.contentSize.height/2);
[self addChild:dial];
self.isTouchEnabled = YES;

[self scheduleUpdate];
}

return self;
}

-(void) ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

NSLog(@"Touch begun");

}

-(void)update:(ccTime) dt{

dial.rotation = cocosAngle;
}

-(void) ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{

NSLog(@"Touch moved");

UITouch *touch = [touches anyObject];
CGPoint touchLocation = [touch locationInView:[touch view]];

CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:touchLocation];

CGPoint vector = ccpSub(touchingPoint, dial.position);
CGFloat rotateAngle = -ccpToAngle(vector);

deltaAngle = CC_RADIANS_TO_DEGREES( rotateAngle);

}
...
@end`
`
This is the scene. I am trying to keep it as simple as possible for now. I just began prototyping and already hit this speed bump. I have searched everywhere and tried everything I could think of but cannot get it to do what I want.

Posted 1 year ago #
paullstanley
Member

bump. I desperately need a couple bumps in the right direction here. There is no documentation to my knowledge covering this problem.

Posted 1 year ago #
paullstanley
Member

Is my problem not described accurately enough? This seems to be a common problem others face too with no distinct solution for us newbie programmers. I tried acquiring the angle in ccTouchesBegan the same way I did in ccTouchesMoved. After that I stored it in a variable. I subtracted that variable from the angle acquired in ccTouchesMoved. I think from here I need some sort of if statement comparing that variable to the current angle? I am not sure where to go from here...

Posted 1 year ago #
Benihana
Member

It's not that you're not describing it accurately, it's just hard to follow your explanation of what it is doing and how that differs from what you want. You're leaving out parts of the code that are relevant (how deltaAngle is used) and posting parts that aren't relevant (initialization).

If you don't want the cylinder to "lock orbits" with the touch, you need to capture the first touch (in touch began) and constantly update the previous touch so you have a relative angle. So use an ivar, "previousTouchAngle," calculate the difference between the new touch and the previousTouchAngle, and add that delta to your cylinder's rotation.

You may find it looks more realistic if you use touches to apply acceleration instead of directly affecting rotation. Throw in a damper that reduces velocity every tick if it is not 0. Just an idea, don't really know what your plan is. ;)

Edit: Your backticks need to be on separate lines.

Posted 1 year ago #
paullstanley
Member

Thank you so much for your reply. I cannot wait to try it, it sounds reasonable and like it will work. As for deltaAngle a pointer reference to CGFloat within the header file. Also there was a typo wich I changed(Within the update method the dials rotation was supposed to equal deltaAngle). Also Within the init method I intialize the deltaAngle at 0. Beyond that what you see is the only thing I have been able to be remotely successful with. Again thank you so much. I will try out your suggestions and report back!

Posted 1 year ago #

paullstanley
Member

OK!! Thank you soooooo much Benihana! life saver man. Let me try and return the favor now to anyone else who may even be greener than I see how I overcame this problem. I did not even need to capture anything within ccTouchesBegan, I managed all the angles in the ccTouchesMoved.

interface MainScene : CCLayer {
	CCSprite *dial;

	CGFloat dialRotation;

}

+ (id)scene;

@end
---------------------------------
@implementation MainScene

+ (id)scene
{
	CCScene *scene = [CCScene node];
	CCLayer *layer = [MainScene node];
	[scene addChild:layer];

	return scene;
}

- (id)init
{
	if((self = [super init])) {
		CCLOG(@"MainScene init");

		CGSize size = [[CCDirector sharedDirector]winSize];

		dial = [CCSprite spriteWithFile:@"dial.png"];
		dial.position = ccp(size.width/2,dial.contentSize.height/2);
	         [self addChild:dial];

		self.isTouchEnabled = YES;
		[self scheduleUpdate];

	}
	return self;
}

- (void)dealloc
{
	[super dealloc];
}

- (void)update:(ccTime)delta
{
	dial.rotation = dialRotation;
}

- (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{

}

- (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
	UITouch *touch = [touches anyObject];

	//acquire the previous touch location
	CGPoint firstLocation = [touch previousLocationInView:[touch view]];
	CGPoint location = [touch locationInView:[touch view]];

    //preform all the same basic rig on both the current touch and previous touch
	CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:location];
	CGPoint firstTouchingPoint = [[CCDirector sharedDirector] convertToGL:firstLocation];

	CGPoint firstVector = ccpSub(firstTouchingPoint, dial.position);
	CGFloat firstRotateAngle = -ccpToAngle(firstVector);
	CGFloat previousTouch = CC_RADIANS_TO_DEGREES(firstRotateAngle);

	CGPoint vector = ccpSub(touchingPoint, dial.position);
        CGFloat rotateAngle = -ccpToAngle(vector);
	CGFloat currentTouch = CC_RADIANS_TO_DEGREES(rotateAngle);

	//keep adding the difference of the two angles to the dial rotation
	dialRotation += currentTouch - previousTouch;
}

- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{

}

Works like a charm. I had already planned on putting other variables into the velocity of the rotation like you suggested. I want the distance and speed your fingers move to effect how fast and long it will spin.

Posted 1 year ago #

SimzStudios
Member

@ Benihana

How would one go about using touch to apply acceleration rather then directly affecting sprite rotation? I am just polishing up my game and I would like things looking a bit more realistic :)

Posted 9 months ago #

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