Scaling Physics Bodies in Xcode Spritekit

Question

I recently came across an issue where I would increase the size of a node, but the physics body would remain the same size. I tried to look up solutions to this with no succ

Answer 1

this is strange you can do it add physics body before adding it to the SKNode or SKScene for e.g.

SKTexture  *texture=[_gameTexture textureNamed:@"mysprite"];
SKSpriteNode *bubble=[SKSpriteNode spriteNodeWithTexture:texture];
bubble.anchorPoint=CGPointMake(0.5,0.5);
//_bubble.name=[@"bubble" stringByAppendingFormat:@"%d ",index];
bubble.name=newcolor;

// _bubble.userInteractionEnabled=YES; _bubble.position=CGPointMake(newPosition.x, newPosition.y);

//
bubble.physicsBody=[SKPhysicsBody bodyWithCircleOfRadius:60];
bubble.physicsBody.dynamic=NO;
bubble.physicsBody.linearDamping=0;
bubble.physicsBody.restitution=0;


bubble.physicsBody.density=1;
bubble.physicsBody.allowsRotation=NO;
bubble.physicsBody.affectedByGravity=NO;
//_bubble.physicsBody.velocity=CGVectorMake([self getRandomNumberBetween:-10 to:7], [self getRandomNumberBetween:-10 to:7]);
//  _bubble.physicsBody.usesPreciseCollisionDetection=YES;


bubble.physicsBody.categoryBitMask=ballCategory;
bubble.physicsBody.collisionBitMask=ballCategory | pathCategory ;
bubble.physicsBody.contactTestBitMask=ballCategory | pathCategory ;

[self addChild:_bubble];


bubble.xScale=_bubble.yScale=2;
bubble.alpha=0.5;

Answer 2

I thought this won't work, but it looks like that physics body is scaled after all. Here is the code which can reproduce physics body scaling on iOS8 :

- (void)didMoveToView:(SKView *)view {
  /* Setup your scene here */

    SKSpriteNode *s = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(100,100)];
    s.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMinY(self.frame)+100);
    s.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:s.size];

    s.physicsBody.dynamic = YES;
    
    s.physicsBody.affectedByGravity = NO;

    [self addChild:s];
    
    [s runAction:[SKAction scaleTo:0.3f duration:5]];

    [s.physicsBody applyImpulse:CGVectorMake(0,30)];
  
}

If I recall correctly , this wasn't worked earlier, but I just tried it and it looks like it work. Still, this is not fully tested and I am not sure if this will mess up the physics simulation. Contact detection will probably work though. I just wanted to show that actual physics bodies are scaled when sprite is scaled . Here is the result:

From the gif above it can be seen that physics body is scaled along with sprite (without re-creating another different sized physics body). The blue bounding box around the sprite is visual representation of sprite's physics body (enabled in view controller with skView.showsPhysics = YES);