为什么SCNPhysicsBody在设置eulerAngles时会重置位置？

问题描述 投票：0回答：4

我正在尝试使用 SceneKit 为 tvOS 开发游戏，但遇到了问题。 当我在向物理主体施加脉冲之前设置节点的 eulerAngle 时，节点将重置到其原始位置。

我原本希望看到节点在地板平面上移动，但每次点击时，节点都会在施加脉冲之前移动到原点位置。

我是这个框架的新手，所以我想知道错误在哪里。 我正在使用带有 tvOS 9.0 和 XCode 7.1.1 的新 AppleTV

要重现它，您可以创建一个新的 xcode 项目（Game for tvOS）并用以下代码替换 GameViewController.m：

#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

如果您注释设置欧拉角的行（在handleTap方法中），则不会出现问题。

objective-c scenekit tvos apple-tv scnnode
4个回答
5
投票

来自 Apple 的 SCNPhysicsBody 文档：

如果更改受物理影响的节点的变换值（或作为变换组件的任何其他属性，例如位置和旋转），SceneKit 会重置该节点的物理模拟。

物理模拟值位于 presentationNode 属性中。因此，在您的情况下，要采取的方法是在应用转换之前复制表示节点的位置，然后将其写回：

SCNVector3 nodePosition = [[node presentationNode] position];
SCNVector3 shipPosition = [[ship presentationNode] position];

[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);

[node setPosition: nodePosition];
[ship setPosition: shipPosition];
4
投票

我找到了问题的答案。

基于这个答案： https://stackoverflow.com/a/28921103/2845875

我意识到我必须在应用变换之前从场景树中删除节点，然后重新插入它们。

按照我的示例，这里是代码：

SCNNode *root = node.parentNode;
[node removeFromParentNode];
[ship removeFromParentNode];

[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];

node.eulerAngles = SCNVector3Make(0, angle, 0);
ship.eulerAngles = SCNVector3Make(0, angle, 0);

[root addChildNode:node];
[root addChildNode:ship];
0
投票

Bon，6 年后...iOS 15、Swift 5.x 在同一个节点上做动画和物理似乎仍然很痛苦。

这是之前答案的快速版本。请注意，我并没有尝试在渲染的每一帧中设置动画，因为从性能角度来看，它 [2020 M1 MBP] 如果我这样做，它就会杀死我的机器。 [肯定是循环寻找孩子的问题]。

“node”是“parentNode”的子节点。物理正在改变“parentNode”。与此同时，我正在旋转子“节点”。

@MainActor class SceneDelegate: NSObject, SCNSceneRendererDelegate {
var share = Common.shared
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
    
    if time > spawnTime2 && !share.landed {
        renderer.scene?.rootNode.childNodes.filter({ $0.name == "coreNode" }).forEach({ parentNode in
            share.updateVelocity(figure: (parentNode.physicsBody?.velocity.y)!)
        })
    }
    
    if time > spawnTime && !share.landed {
        print("spawn")
        renderer.scene?.rootNode.childNodes.filter({ $0.name == "coreNode" }).forEach({ parentNode in
            let savePos = parentNode.presentation.position

            parentNode.childNodes.filter({ $0.name == "shipNode" }).forEach({ node in
                let quaternion = simd_quatf(angle: GLKMathDegreesToRadians(1), axis: simd_float3(0,1,0))
                node.simdOrientation = quaternion * node.simdOrientation

//node.eulerAngles = SCNVector3(x: 0, y:GLKMathDegreesToRadians(rotater) , z:0) 旋转器 += 1 })

            parentNode.position = savePos
           
        })
    }
}

func renderer(_ renderer: SCNSceneRenderer, didRenderScene scene: SCNScene, atTime time: TimeInterval) {
    spawnTime = time + TimeInterval(0.015)
    spawnTime2 = time + TimeInterval(0.018)
}
}

四元数和欧拉旋转都有效，这就是我保留代码的原因。

spawnTime 速度是一个对我有用的捏造数字。太快了，它会跳，太慢了，根本不起作用。

0
投票

添加到 Ramy Al Zuhouri 的答案中，我是这样做的：

// get the presentation variables

let position = self.snowBoard!.presentation.position
let worldPosition = self.snowBoard!.presentation.worldPosition
let eulerAngles = self.snowBoard!.presentation.eulerAngles

// apply the rotational transform

self.snowBoard?.eulerAngles = SCNVector3(
    x: eulerAngles.x,
    y: eulerAngles.y + convertToRadians(angle: 1.5) ,
    z: eulerAngles.z
)

// set the position and world position using the original presentation variables

self.snowBoard?.position = position
self.snowBoard?.worldPosition = worldPosition
最新问题
© www.soinside.com 2019 - 2024. All rights reserved.