SpriteKit side scrolling doesn't update physicsWorld

Question

Following the example here (except in Objective C) and the standard Apple documentation, I discovered that the physicsWorld doesn\'t update its positions when

Answer 1

I noticed that once the monkey makes contact, all of the physics bodies snap back to their proper locations. However, a joints anchorPoint ends up in the wrong place.

I added the following convenience method to my GameScene.m.

-(CGPoint)convertSceneToFrameCoordinates:(CGPoint)scenePoint
{
    CGFloat xDiff = myWorld.position.x - self.position.x;
    CGFloat yDiff = myWorld.position.y - self.position.y;
    return CGPointMake(scenePoint.x + self.frame.size.width/2 + xDiff, scenePoint.y + self.frame.size.height/2 + yDiff);
}

I use this method to add joints. It handles all of the coordinate system transformations that need to be dealt with that lead to the issue raised in this question. For example, the way I add joints

    CGPoint convertedRopePosition = [self convertSceneToFrameCoordinates:ropePhysicsBody.node.position];
    SKPhysicsJointPin *jointPin = [SKPhysicsJointPin jointWithBodyA:monkeyPhysicsBody bodyB:ropePhysicsBody anchor:convertedRopePosition];
    jointPin.upperAngleLimit = M_PI/4;
    jointPin.shouldEnableLimits = YES;
    [self.scene.physicsWorld addJoint:jointPin];

Answer 2

I don't know what's changed in the last 2 years, but the other answer here didn't work anymore. Instead, now I combine the rope segments position with its parent's (the full rope). So I just do

CGPoint convertedRopePosition = CGPointMake(ropePhysicsBody.node.parent.position.x + ropePhysicsBody.node.position.x, ropePhysicsBody.node.parent.position.y + ropePhysicsBody.node.position.y);
SKPhysicsJointPin *jointPin = [SKPhysicsJointPin jointWithBodyA:monkeyPhysicsBody bodyB:ropePhysicsBody anchor:convertedRopePosition];

This is needed because the rope segment is placed under the full length of the rope, so it's position is relative to the full rope rather than the scene.