CODEWITHSUNDEEP
objective-ccalayercollision
jmg14
jmg14

Reputation: 1

Using CGRectIntersectsRect to detect a collision between two CAlayers

I am trying to use CGRectIntersectsRect to detect a collision between two CAlayers. One is part of a hierarchy of layers, and the other is a sublayer of the main view. I have tried this:

Accessing presentationLayer of an animation to detect collisions

It does not work with any consistency. Here is what I have right now. "LegLowerLeft" is part of a hierarchy of CAlayers and "rec2" is a subview of the main view. Thanks in advance for any help.:

-(void) checkForCollisionWithRec{
  if(CGRectIntersectsRect(((CALayer*)self.creature.legLowerLeft.presentationLayer).frame,
                            ((CALayer*)rec2.presentationLayer).frame))

    { NSLog(@"Collision detected"); }

   else{NSLog(@"No collision detected");}
 }

Upvotes: 0

Views: 596

Answers (1)

Rob Napier
Rob Napier

Reputation: 299305

The frame of a layer is in the coordinate space of its superview. If two layers have different superviews, then you cannot compare their frames directly. You must convert them to a consistent coordinate space.

CALayer *layer1 = self.creature.legLowerLeft.presentationLayer;
CALayer *layer2 = rec2.presentationLayer;

CGRect frame1 = layer1.frame;
CGRect frame2 = [layer1 convertRect:layer2.frame fromLayer:layer2];

if(CGRectIntersectsRect(frame1, frame2))
{
  NSLog(@"Collision detected");
}
else
{
  NSLog(@"No collision detected");
}

Upvotes: 3

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