How to make a sprite follow a path Cocos2d

gab20 · May 2012

Hi, I have been working on a game where the player should be able to make a path or a line that a sprite should follow.

I already have a somewhat working code I have a mutable array (to record touch locations) and a draw method (to draw the line) It works but I just can't get a line of code working which is supposed to be where the magic happens to move the sprite through the locations recorded in the array please take a look at my code thanks.

-(void) ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event  { 
    //remove objects each time the player makes a new path
    [toucharray removeAllObjects];
}

here I record the touch locations in the array

-(void) ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event  {    
    UITouch *touch = [ touches anyObject];
    CGPoint new_location = [touch locationInView: [touch view]];
    new_location = [[CCDirector sharedDirector] convertToGL:new_location];
    
    CGPoint oldTouchLocation = [touch previousLocationInView:touch.view];
    oldTouchLocation = [[CCDirector sharedDirector] convertToGL:oldTouchLocation];
    oldTouchLocation = [self convertToNodeSpace:oldTouchLocation];

    // add touches to the touch array 
   [toucharray addObject:NSStringFromCGPoint(new_location)];
    [toucharray addObject:NSStringFromCGPoint(oldTouchLocation)];

}

-(void)draw
{
    glEnable(GL_LINE_SMOOTH);
    
    for(int i = 0; i < [toucharray count]; i+=2)
    {
        CGPoint start = CGPointFromString([toucharray objectAtIndex:i]);
        CGPoint end = CGPointFromString([toucharray objectAtIndex:i+1]);
        ccDrawLine(start, end);
    }
}

this is the part I'm having problems with. this line should be able to move the sprite but I always get a message "Passin 'id' to parameter of incompatible type 'CGPoint' aka 'struct CGPoint'" it highlights [toucharray objectAtIndex:0]
I don't understand if my draw method uses my array and works perfectly why won't this line read from my array too?
moreover I don't really ger the ccpAdd(ccpMult) I don't understand well what it does if someone would help me or point me in the right direction I would appreciate it a lot!

-(void) ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
 UITouch* myTouch = [touches anyObject];
    CGPoint location = [myTouch locationInView: [myTouch view]];
    location = [[CCDirector sharedDirector]convertToGL:location];

  // HERE IS THE LINE

 _sprite.position = ccpAdd(ccpMult([toucharray objectAtIndex:0], progress), ccpMult([toucharray objectAtIndex:0+1], 1-progress));

hazza · May 2012

ccpMult(a, b) works like ccp(a.x * b.x, a.y * b.y)
ccpAdd(a, b) works like ccp(a.x + b.x, a.y + b.y)

gab20 · May 2012

thanks for the reply! now that part makes more sense to me.

although I'm still stuck trying to move the sprite position according to the location stored in the array.

Does anyone know if the reason why it's not working is because of the way I'm storing the CGPoint locations in the array?

// touches to the touch array
[toucharray addObject:NSStringFromCGPoint(new_location)];
[toucharray addObject:NSStringFromCGPoint(oldTouchLocation)];

and then using this line to move the sprite

_sprite.position = ccpAdd(ccpMult([toucharray objectAtIndex:currentIndex], progress), ccpMult([toucharray objectAtIndex:currentIndex+1], 1-progress));

or is there any other way to actually do this? thanks

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How to make a sprite follow a path Cocos2d

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