如何防止SKSpriteNode的子进程与其父进程一起旋转？

Question

我正在使用SpriteKit编写一个涉及许多标记球的iOS游戏.我正在通过构建一个包含2个子节点的父SKSpriteNode构建这些'rollingBalls':

a)SKShapeNode(实际圆形)

b)和SKLabelNode(标签)

球将在整个屏幕上移动,彼此之间以及其他物体在2维中相互作用,并且完全取决于预期的物理(想想台球).但是,如果可能的话,我希望标签不与父母一起旋转,这样它在任何时候都很容易阅读.

最简单的方法是什么？

标签不应该是容器的孩子吗？还有其他方法可以将它钉在球形状上吗？或者我可以在标签上设置一些属性等等？

这就是我现在所拥有的:

double ballDiameter = 40;
UIBezierPath* ovalPath = [UIBezierPath bezierPathWithOvalInRect: 
                            CGRectMake(-ballDiameter / 2, -ballDiameter / 2, 
                                        ballDiameter, ballDiameter)];

SKSpriteNode *container = [[SKSpriteNode alloc]init];

container.name = @"rollingBall";

SKShapeNode *ballShape = [[SKShapeNode alloc] init];
ballShape.path = ovalPath.CGPath;

SKLabelNode *ballLabel = [SKLabelNode labelNodeWithFontNamed:@"Arial"];
ballLabel.text = @"some random string";
ballLabel.horizontalAlignmentMode = SKLabelHorizontalAlignmentModeCenter;
ballLabel.verticalAlignmentMode = SKLabelVerticalAlignmentModeCenter;
ballLabel.position = CGPointMake(0,0);

[container addChild:ballShape];
[container addChild:ballLabel];

container.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ballDiameter / 2];
container.physicsBody.usesPreciseCollisionDetection = YES;

Answer 1

将所有标签放在一个容器中,将标签添加到关联节点的userData,然后更新标签位置.

// Add a container as a scene instance variable.
SKNode *labels;

- (void)addLabelContainer
{
    labels = [SKNode node];
    [self addChild:labels];
}

- (void)addLabelForNode:(SKNode*)node
{
    SKLabelNode *label = [SKLabelNode labelNodeWithFontNamed:@"Chalkduster"];
    node.userData = [NSMutableDictionary dictionaryWithObject:label forKey:@"label"];
    label.text = node.name;
    label.fontSize = 5;
    label.zPosition = node.zPosition + 1;
    [labels addChild:label];
}

- (void)removeLabelForNode:(SKNode*)node
{
    [[node.userData objectForKey:@"label"] removeFromParent];
    [node.userData removeObjectForKey:@"label"];
}

- (void)update:(NSTimeInterval)currentTime
{
    for (SKNode *node in self.children) {
        SKNode *label = (SKLabelNode*)[node.userData objectForKey:@"label"];
        if (label) {
            label.position = node.position;
        }
    }
}

请参阅https://github.com/pmark/MartianRover/blob/master/hiSpeed/hiSpeed/Scenes/LimboScene.m

Answer 2

这似乎有效

-(void) didSimulatePhysics
{
    [self enumerateChildNodesWithName:@"ball" usingBlock:^(SKNode *node, BOOL *stop) {

        for (SKNode *n in node.children) {
            n.zRotation = -node.zRotation;
        }

    }];
}

Answer 3

一种潜在的、超级简单的解决方案：

container.physicsBody.allowsRotation = NO

但这当然会阻止整个精灵旋转。