cocos2d pixel collision detection - iphone

Question

i am currently writing a game with a number of rectangles (say 30), if a user clicks on one of the four sides a certain action will need to be taken. Trouble is each card will have the same side which will perform this action. For example with rectangle 1 the side which will perform this action will be the left, but rectangle 3 the side will be the top side. My guess is a pixel collision detection is needed here. What do you guys think? Also is there a good example on pixel collision using cocos2s out there?

Answer 1

You can simply use following code
if (CGRectIntersectsRect(Rect1, Rect2))
{
//Your code ...
}
USING above CGRectIntersectsRect you can detect the collision pixels within a rectangular area.

Answer 2

yes good point, the solution was a little messy but it worked, this is what i did: I subclassed CCSprite and created a new attribute called state saving the current position if rotated relative to that rotation. Depending on what side was touched i would use that information to determine which side of the rectangle was touched. –
if((spriteCentre1.x < spriteCentre2.x) && (xAxisDiff < yAxisDiff))
{
[HelloWorldLayer whichSideTouched:sprite1 sideTouched:kStateRightPlus touchingSprite:sprite2];
}
+(int)whichSideTouched:(SpriteCard *)sprite sideTouched:(int)touched touchingSprite:(SpriteCard *)sprite2
{
switch (sprite.state) {
case kStateUpPlus:
case kStateUpMinus:
if(touched == kStateDownPlus)
{
NSLog(# "touched up ");
[sprite setTop:sprite2];
retValue = kStateUpPlus;
}
else if(touched == kStateRightPlus)
{
NSLog(# "touch left");
[sprite setRight:sprite2];
retValue = kStateLeftPlus;
}
}

Answer 3

Thanks for that Dhaval, here is the code i wrote a future reference for anyone who wishes to do similar, it can be further fine tuned, if i figure out a more accurate way of doing this i will update this thread accordingly
-(void)touchWhichSide:(CCSprite *)sprite1 collidingSprite:(CCSprite *)sprite2
{
BOOL retValue = NO;
CGPoint spriteCentre1 = sprite1.position;
CGPoint spriteCentre2 = sprite2.position;
NSLog(#"X %f",spriteCentre2.x - spriteCentre1.x);
NSLog(#"Y %f",spriteCentre1.y - spriteCentre2.y);
float xAxisDiff = spriteCentre1.x - spriteCentre2.x;
float yAxisDiff = spriteCentre1.y - spriteCentre2.y;
NSLog(#"x axis %f",xAxisDiff);
NSLog(#"y axis %f",yAxisDiff);
if((spriteCentre1.x < spriteCentre2.x) && (xAxisDiff < yAxisDiff))
{
NSLog(#"right touch");
}
else if((spriteCentre2.x < spriteCentre1.x) && (xAxisDiff > yAxisDiff))
{
NSLog(#"left touch");
}
else if((spriteCentre2.y < spriteCentre1.y) && (yAxisDiff > xAxisDiff))
{
NSLog(#"Bottom touch");
}
else if((spriteCentre1.y < spriteCentre2.y) && (yAxisDiff < xAxisDiff))
{
NSLog(#"Top touch");
}
}