SCNSphere不适当旋转

Question

我正在用SpriteKit制作一个游戏，在这个游戏的主菜单中有一个SK3DNode，它包含一个设计用来包含旋转行星的SCNScene。我把它设成这样

//create scene
SCNScene *planetScene = [[SCNScene alloc] init];
SCNSphere *planet = [SCNSphere sphereWithRadius:2.0];
planet.firstMaterial.diffuse.contents = [UIImage imageNamed:@"Planet_2_d.png"];
SCNNode *plNode = [SCNNode nodeWithGeometry:planet];
[planetScene.rootNode addChildNode:plNode];

//animate planet
CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"rotation"];
rotationAnimation.toValue = [NSValue valueWithSCNVector4:SCNVector4Make(0, 1, 0, M_PI * 2)];
rotationAnimation.duration = 6; // One revolution in ten seconds.
rotationAnimation.repeatCount = FLT_MAX; // Repeat the animation forever.
[plNode addAnimation:rotationAnimation forKey:nil]; // Attach the animation to the node to start it.

//create and add sprite kit node
SK3DNode *planetNode = [[SK3DNode alloc] initWithViewportSize:CGSizeMake(125, 125)];
planetNode.scnScene = planetScene;
planetNode.position = CGPointMake(loadGameButton.position.x - 200, CGRectGetMidY(self.frame));
planetNode.autoenablesDefaultLighting = YES;
planetNode.playing = YES;

id s1 = [planetNode valueForKey:@"_scnRenderer"];
NSLog(@"%@", s1);

[self addChild:planetNode];

这是按计划进行的，除了行星做的不仅仅是旋转。除了旋转外，它还会放大和移出。在上面的代码中，我看不到任何东西会导致它以这种方式运行。我怎样才能让地球旋转而不是缩放呢？

Answer 1

这个问题是通过在这样的场景中增加一个摄像机来解决的。

SCNCamera *camera = [SCNCamera camera];
camera.xFov = 0;
camera.yFov = 0;
camera.zNear = 0.0;
camera.zFar = 10.0;
SCNNode *cameraNode = [SCNNode node];
cameraNode.camera = camera;
cameraNode.position = SCNVector3Make(0, 0, 3);
[planetScene.rootNode addChildNode:cameraNode];

planetNode.pointOfView = cameraNode;