SKEmitterNode targetNode路径跟踪反转

Question

我创建了一个SKEmitterNoder (标准Fire.sks模板)&将它添加到一个名为SKSpriteNode的SKSpriteNode中。问题是，我通过教程学习了iOS游戏的教程&他们教我创建平铺地图的方法，本质上是将它们翻转到init上，这样(0，0)就会出现在屏幕的左下角，而不是左上角。我认为这影响了我的SKEmitterNode targetNode属性，因为当球在场景中移动时，发射节点就会向相反的方向移动。谁能告诉我该怎么做才能改变这一切？我不能改变世界参数，所以我需要一些东西来改变SKEmitterNode的轨迹，这样它才能正确地跟随球节点。以下是我的当前代码：

NPCBall *ball   = [[NPCBall alloc] initWithBallType:BallTypeRed andName:@"Ball Red"];
ball.position   = CGPointMake(x + w/2, y + h/2);
ball.zPosition  = -104.0;
[_entityNode addChild:ball];

//Create a random Vector.dx & dy for the NPC. This will apply a random impulse to kick start NPC non-stop movement.
[ball.physicsBody applyImpulse:CGVectorMake([self randomVectorGeneration].dx, [self randomVectorGeneration].dy)];

//Create a particle for the ball (fire).
SKEmitterNode *emitFire = [NSKeyedUnarchiver unarchiveObjectWithFile:[[NSBundle mainBundle] pathForResource:@"Particle_Fire" ofType:@"sks"]];
emitFire.position       = CGPointMake(ball.position.x, ball.position.y);
emitFire.targetNode = ball;
[_entityNode addChild:emitFire];

P.S. _entityNode是一个SKNode，它加上了球和SKEmitterNode火。这反过来又是一个名为SKNode的_worldNode的子代。_worldNode是自我的子代(这是SKScene)。这个_worldNode是从左下角开始的(0，0)坐标。

Answer 1

我的一个朋友找到了解决这个问题的办法。我在这里张贴它，以防有人也有一个倒置的贴图，其中(0，0)坐标在场景的左下角。

    //Create a ball sprite.
    SKSpriteNode *ball = [SKSpriteNode spriteNodeWithColor:[SKColor redColor] size:CGSizeMake(20, 20)];
    ball.position   = CGPointMake(_worldNode.frame.size.width/2, _worldNode.frame.size.height/2);
    [_entityNode addChild:ball]; //<--_entityNode is also an SKNode. It's a child of _worldNode.
    ball.zPosition  = -104.0;

    //Create a random Vector.dx & dy for the NPC. This will apply a random impulse to kick start NPC non-stop movement.
    [ball.physicsBody applyImpulse:CGVectorMake([self randomVectorGeneration].dx, [self randomVectorGeneration].dy)];


    //Create a particle effect for the ball.
    SKEmitterNode *emitFire = [NSKeyedUnarchiver unarchiveObjectWithFile:[[NSBundle mainBundle] pathForResource:@"Particle_Fire" ofType:@"sks"]];
    emitFire.name           = @"Fire Emitter";
    emitFire.targetNode     = _worldNode; //<-- This is the demon. Make the emitter follow this SKNode since it moves when the ball moves. Everything in my game is a child of _worldNode.
    [ball addChild:emitFire]; //Add the emitter to the ball.