Collision with sprite having another sprite as parent - cocos2d-iphone

Question

Seems impossible but there has to be a solution.
I have the following classes:
#interface EnemiesEntities : CCSprite {
bool isFunctional;
CCSprite * laserBeam; // <----------- !!!!! That's where I want to check the collision.
CCSprite * leftRingEffect;
CCSprite * rightRingEffect;
}
#interface ShipEntity : CCSprite
{}
And I simply want to verify the collision between the ShipEntity and the laserBeam sprite (laserBeam is a member variable and child of EnemiesEntities class).
The method [laserBeam boundingBox] doesn't work as the boundingBox converts the coordinates relative to the parent node.
I tried thend adding to CCNode a method computing the boundingBox relative to the world but also this one did not work:
- (CGRect) worldBoundingBox
{
CGRect rect = CGRectMake(0, 0, contentSize_.width, contentSize_.height);
return CGRectApplyAffineTransform(rect, [self nodeToWorldTransform]);
}
I checked online and found only unuseful (to me) answers to the same question.
I then tried a different approach and tried to start from the boudningBox and change the position of the rectangle so obtained in respect to the parent position as following:
-(BOOL) collidesWithLaser:(CCSprite*)laserBeam
{
CGPoint newPosition = [laserBeam convertToWorldSpace:laserBeam.position];
[laserBeam worldBoundingBox];
CGRect laserBoundingBox = [laserBeam boundingBox];
CGRect laserBox = CGRectMake(laserBeam.parent.position.x, laserBeam.parent.position.y, laserBoundingBox.size.width, laserBoundingBox.size.height);
CGRect hitBox = [self hitBox];
if(CGRectIntersectsRect([self boundingBox], laserBox))
{
laserBeam.showCollisionBox=TRUE;
return TRUE;
}
else {
return FALSE;
}
}
Unfortunately this does work only when the rotation of the parent sprite is set to 0.0 but when it actually changes then it doesn't work (is probably because the boundingBox is relative to the parent node and not world).
I am a bit lost and was wondering if any of you had better luck in solving this problem and which solution (code snippets please :)) you used.
EDIT in Response to #LearnCocos2D answer:
I followed the suggestion and added the following code which doesn't work properly (e.g. try with an EnemiesEntities object is rotated to -130.0f).
-(BOOL) collidesWithLaser:(CCSprite*)laserBeam
{
CCLOG(#"rotation %f", laserBeam.rotation);
CGRect laserBoundingBox = [laserBeam boundingBox];
laserBoundingBox.origin = [self convertToWorldSpace:laserBeam.position];
CGRect shipBoundingBox = [self boundingBox]; //As we are in ShipEntity class
shipBoundingBox.origin = [self convertToWorldSpace:shipBoundingBox.origin];
//As this method is in the ShipEntity class there is no need to convert the origin to the world space. I added a breakpoint here and doing in this way the CGRect of both ShipEntity and gets misplaced.
if(CGRectIntersectsRect(shipBoundingBox, laserBoundingBox))
{
return TRUE;
}
else {
return FALSE;
}
}

Answer 1

The problem is in this line I think:
CGPoint newPosition = [laserBeam convertToWorldSpace:laserBeam.position];
laserBeam isn't in laserBeam's space but laserBeams parent space. So the correct is:
CGPoint newPosition = [[laserBeam parent] convertToWorldSpace:laserBeam.position];
The whole code
-(BOOL) collidesWithLaser:(CCSprite*)laserBeam
{
CGPoint newPosition = [laserBeam convertToWorldSpace:laserBeam.position];
CGRect laserBoundingBox = [laserBeam boundingBox];
laserBoundingBox.origin = newPosition;
CGRect hitBox = [self boundingBox];
hitbox.origin = [[self parent] convertToWorldSpace:hitbox.origin];
if(CGRectIntersectsRect(hitbox, laserBoundingBox))
{
laserBeam.showCollisionBox=TRUE;
return TRUE;
}
else {
return FALSE;
}
}

Answer 2

for both boundingboxes do:
bbox.origin = [self convertToWorldSpace:bbox.origin];
now you can compare the rects...
Update to update:
The boundingBox is an axis-aligned bounding box.
If the entity is rotated, the bounding box size increases to encompass all of the sprite's corners. Therefore collision (intersection) may be detected even relatively far away from the node when testing axis-aligned bounding boxes.
In ccConfig.h there's an option you can turn on to draw sprite bounding boxes, you should set this to 1 to see the bounding boxes: #define CC_SPRITE_DEBUG_DRAW 1
For oriented rectangles you need a different data structure and different intersection test, see for example this tutorial.