Estou tentando usar o SceneKit para desenvolver um jogo para o tvOS e estou tendo um problema. Quando defino o eulerAngle do nó antes de aplicar um impulso ao physicsBody, o nó é redefinido para sua posição original.

Eu esperava ver os nós se movendo no plano do piso, mas em cada torneira os nós são movidos para a posição de origem antes que o impulso seja aplicado.

Sou novo no uso dessa estrutura, então me pergunto onde está o erro. Estou usando o novo AppleTV com tvOS 9.0 e XCode 7.1.1

Para reproduzi-lo, você pode criar um novo projeto xcode (Game for tvOS) e substituir o GameViewController.m por este código:

#import "GameViewController.h"

SCNNode *ship;
SCNNode *node;
SCNNode *ground;

@implementation GameViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // create a new scene
    SCNScene *scene = [[SCNScene alloc] init];
    scene.physicsWorld.gravity = SCNVector3Make(0, -800, 0);

    // create and add a camera to the scene
    SCNNode *cameraNode    = [SCNNode node];
    cameraNode.camera      = [SCNCamera camera];
    cameraNode.camera.zFar = 10000;
    [scene.rootNode addChildNode:cameraNode];

    // place the camera
    cameraNode.position = SCNVector3Make(0, 64, 64);

    // create and add a light to the scene
    SCNNode *lightNode   = [SCNNode node];
    lightNode.light      = [SCNLight light];
    lightNode.light.type = SCNLightTypeOmni;
    lightNode.position   = SCNVector3Make(0, 10, 10);
    [scene.rootNode addChildNode:lightNode];

    // create and add an ambient light to the scene
    SCNNode *ambientLightNode    = [SCNNode node];
    ambientLightNode.light       = [SCNLight light];
    ambientLightNode.light.type  = SCNLightTypeAmbient;
    ambientLightNode.light.color = [UIColor darkGrayColor];
    [scene.rootNode addChildNode:ambientLightNode];

    SCNGeometry *geometry;
    SCNMaterial *material;
    SCNNode *tempNode;
    SCNPhysicsShape* shape;
    SCNPhysicsBody* body;

    //--
    SCNScene *loaded = [SCNScene sceneNamed:@"art.scnassets/ship.scn"];
    tempNode = [loaded.rootNode childNodeWithName:@"ship" recursively:YES];

    geometry = [SCNCylinder cylinderWithRadius:16 height:8];
    shape    = [SCNPhysicsShape shapeWithGeometry:geometry options:nil];

    tempNode.physicsBody = [SCNPhysicsBody bodyWithType:SCNPhysicsBodyTypeDynamic shape:shape];
    tempNode.physicsBody.restitution      = 1;
    tempNode.physicsBody.friction         = 0.25;
    tempNode.physicsBody.categoryBitMask  = 2;
    tempNode.physicsBody.collisionBitMask = 1;
    tempNode.position = SCNVector3Make(32, 32, 0);
    [scene.rootNode addChildNode:tempNode];
    ship = tempNode;

    //--
    geometry = [SCNCylinder cylinderWithRadius:16 height:8];

    material = [[SCNMaterial alloc] init];
    material.diffuse.contents = UIColor.yellowColor;
    geometry.materials        = @[material];

    shape = [SCNPhysicsShape shapeWithGeometry:geometry options:nil];
    body  = [SCNPhysicsBody bodyWithType:SCNPhysicsBodyTypeDynamic shape:shape];

    tempNode = [SCNNode nodeWithGeometry: geometry];
    tempNode.physicsBody                  = body;
    tempNode.physicsBody.restitution      = 1;
    tempNode.physicsBody.friction         = 0.25;
    tempNode.physicsBody.categoryBitMask  = 2;
    tempNode.physicsBody.collisionBitMask = 1;
    tempNode.position = SCNVector3Make(0, 32, 0);
    [scene.rootNode addChildNode:tempNode];
    node = tempNode;

    //--
    geometry = [[SCNFloor alloc] init];

    material = [[SCNMaterial alloc] init];
    material.diffuse.contents = UIColor.blueColor;
    geometry.materials        = @[material];

    shape = [SCNPhysicsShape shapeWithGeometry:geometry options:nil];
    body  = [SCNPhysicsBody bodyWithType:SCNPhysicsBodyTypeKinematic shape:shape];

    tempNode = [SCNNode nodeWithGeometry: geometry];
    tempNode.physicsBody = body;
    tempNode.physicsBody.categoryBitMask = 1;
    [scene.rootNode addChildNode:tempNode];
    ground = tempNode;

    //--
    SCNLookAtConstraint * constraint = [SCNLookAtConstraint lookAtConstraintWithTarget: ground];
    constraint.gimbalLockEnabled = YES;
    cameraNode.constraints = @[constraint];

    // configure the SCNView
    SCNView *scnView = (SCNView *)self.view;
    scnView.scene = scene;
    scnView.allowsCameraControl = NO;
    //scnView.antialiasingMode = SCNAntialiasingModeMultisampling2X;
    scnView.debugOptions = SCNDebugOptionShowPhysicsShapes;
    scnView.showsStatistics = YES;
    scnView.backgroundColor = [UIColor blackColor];

    // add a tap gesture recognizer
    UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTap:)];
    NSMutableArray *gestureRecognizers = [NSMutableArray array];
    [gestureRecognizers addObject:tapGesture];
    [gestureRecognizers addObjectsFromArray:scnView.gestureRecognizers];
    scnView.gestureRecognizers = gestureRecognizers;
}

- (void) handleTap:(UIGestureRecognizer*)gestureRecognize
{
    float x = (rand() / (float)RAND_MAX) - 0.5f;
    float y = (rand() / (float)RAND_MAX) - 0.5f;
    float speed = (rand() / (float)RAND_MAX) * 300;

    CGPoint velocity = CGPointMake(x, y);
    float angle = [self AngleBetween:velocity And:CGPointMake(1, 0)] + M_PI_2;

    [node.physicsBody applyForce:SCNVector3Make(velocity.x*speed, 0, velocity.y*speed) impulse:YES];
    [ship.physicsBody applyForce:SCNVector3Make(velocity.x*speed, 0, velocity.y*speed) impulse:YES];

    // if comment these lines the problem doesn't appears
    node.eulerAngles = SCNVector3Make(0, angle, 0);
    ship.eulerAngles = SCNVector3Make(0, angle, 0);
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

- (float) AngleBetween:(CGPoint)_origin And:(CGPoint)_destination
{
    float dotProduct = (_origin.x * _destination.x) + (_origin.y * _destination.y);
    float perpDotProduct = (_origin.x * _destination.y) - (_origin.y * _destination.x);

    return -atan2f(-perpDotProduct, dotProduct);
}

@end

Se você comentar as linhas em que os ângulos de Euler estão definidos (no método handleTap), o problema não aparece.