Ich versuche, mit SceneKit ein Spiel für tvOS zu entwickeln, und habe ein Problem. Wenn ich den eulerAngle des Knotens vor dem Anwenden eines Impulses auf den physicsBody setze, wird der Knoten auf seine ursprüngliche Position zurückgesetzt.

Ich hatte erwartet, dass sich die Knoten in der Ebene des Bodens bewegen, aber bei jedem Tippen werden die Knoten in die Ursprungsposition verschoben, bevor der Impuls angewendet wird.

Ich bin neu in der Verwendung dieses Frameworks, daher frage ich mich, wo der Fehler liegt. Ich benutze das neue AppleTV mit tvOS 9.0 und XCode 7.1.1

Um es zu reproduzieren, kannst du ein neues xcode-Projekt (Game for tvOS) erstellen und den GameViewController.m durch diesen Code ersetzen:

#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

Wenn Sie die Zeilen kommentieren, in denen die Euler-Winkel festgelegt sind (bei der handleTap-Methode), wird das Problem nicht angezeigt.