Sprite 套件：匀速运动时卡顿

Question

Sprite 套件：匀速运动时卡顿

suy*_*ama 3 objective-c game-physics ios sprite-kit

我正在开发一个带有精灵套件的简单飞行游戏。一旦太空船达到最大高度和速度，它就会以恒定的速度飞行。我注意到飞船在不断的飞行过程中会随机结结巴巴。我在这里阅读了有关此问题的所有帖子，但没有任何内容真正有助于 100% 修复它。

为了测试，我编写了一个非常简单的游戏，其中只包含一艘太空船和一个简单的云（代码如下）。但是即使在这个非常简单的游戏中，飞船仍然会卡顿。LOG 显示，即使太空船以恒定速度飞行，太空船的运动也不是随机恒定的。这就是口吃的原因。

希望有人能帮我解决这个问题。感谢您的任何想法。

Sprite 套件、Objective c、Xcode 8.0、测试设备：iPhone 6 - iOS 8.3、iPhone 4s - iOS 9.3.5

CPU：最大 21%，内存：最大 8 MB，FPS：永久 60 FPS

这是我的代码（为简单起见，我将所有代码放在场景类中）

FlightScene.h

#import <SpriteKit/SpriteKit.h>

@interface FlightScene : SKScene <SKPhysicsContactDelegate>

@end

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FlightScene.m

#import "FlightScene.h"

#define  HERO_FLIGHT_LOG    1
//#define  HERO_DEBUG_OVERLAY 1

static const CGFloat kMaxHeroVelocityY = 100.0f;
static const CGFloat kMaxHeroVelocityX = 200.0f;

@implementation FlightScene
{
    SKNode *_world;
    SKSpriteNode *_hero;
    SKSpriteNode *_cloud;

    CGPoint _heroStartPosition;
    CGSize _cloudSize;
    CGFloat _xAdj;

    BOOL _hasBegun;

    // debug
    CGFloat _oldHeroX;
    CGFloat _oldHeroY;
    int _frame;

}

- (void)didMoveToView:(SKView *)view
{
    // Setup your scene here

    [super didMoveToView:view];

    _hasBegun = NO;        
    _cloudSize = CGSizeMake(120, 80);
    _xAdj = _cloudSize.width;
    _heroStartPosition = CGPointMake(60, self.size.height/2);

    [self addWorld];
    [self addHero];
    [self addCloud];

    // debug
    _frame = 0;
    _oldHeroX = 0;
    _oldHeroY = 0;
}

#pragma mark - hero

- (void)addHero
{
    _hero = [SKSpriteNode spriteNodeWithImageNamed:@"Spaceship2"];

    _hero.size = CGSizeMake(80.0f, 70.0f);
    _hero.position = _heroStartPosition;
    _hero.zPosition = 1;

    _hero.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:self.size.width/2.0f];
    _hero.physicsBody.affectedByGravity = NO;
    _hero.physicsBody.dynamic = YES;
    _hero.physicsBody.allowsRotation = NO;
    _hero.physicsBody.mass = 1.0f;
    _hero.physicsBody.linearDamping = 0.0f;
    _hero.physicsBody.friction = 0.0f;

    [_world addChild:_hero];
}

- (void)updateFlying
{
    if(!_hasBegun)
        return;

    CGVector oldVel = _hero.physicsBody.velocity;
    CGVector newVel = oldVel;

    // increase the velocity
    newVel.dx += (kMaxHeroVelocityX - newVel.dx) / 10.0f;
    newVel.dy += (kMaxHeroVelocityY - newVel.dy) / 10.0f;

    // ensure velocity doesn't exceed maximum
    newVel.dx = newVel.dx > kMaxHeroVelocityX ? kMaxHeroVelocityX : newVel.dx;
    newVel.dy = newVel.dy > kMaxHeroVelocityY ? kMaxHeroVelocityY : newVel.dy;

    _hero.physicsBody.velocity = newVel;
}

- (void)limitHeight
{
    const CGFloat maxHeight = self.size.height * 0.8f;
    if(_hero.position.y > maxHeight)
        _hero.position = CGPointMake(_hero.position.x, maxHeight);
}

- (void)updateFlight
{
    // move hero with constant velocity
    [self updateFlying];

    // ensure height doesn't exceed maximum
    [self limitHeight];
}

#pragma mark - game world

- (void)addWorld
{
    _world = [SKNode new];
    [self addChild:_world];
}

- (void)addCloud
{
    _cloud = [SKSpriteNode spriteNodeWithColor:[SKColor lightGrayColor] size:_cloudSize];

    _cloud.anchorPoint = CGPointMake(0, 1); // top left
    _cloud.position = CGPointMake(self.size.width + _cloudSize.width, self.size.height + _cloudSize.height/2);
    _cloud.zPosition = -1;

    [_world addChild:_cloud];
}

#pragma mark - update world

- (void)updateCloud
{
    // reposition the cloud
    if(_world.position.x + _xAdj < -(_cloudSize.width + self.size.width))
    {
        _xAdj += _cloudSize.width + self.size.width;

        CGFloat y = arc4random_uniform(_cloudSize.height - 10);
        _cloud.position = CGPointMake(_xAdj + self.size.width, self.size.height + y);
    }
}

- (void)updateWorld
{
    // move the world
    CGFloat worldX = -(_hero.position.x - _heroStartPosition.x);
    _world.position = CGPointMake(worldX, _world.position.y);

    [self updateCloud];
    [self flightLog];
}

-(void)update:(CFTimeInterval)currentTime
{
    // Called before each frame is rendered

    if(!_hasBegun)
        return;

    _frame++;

    // update hero movement
    [self updateFlight];
}

- (void)didFinishUpdate
{
    if(!_hasBegun)
        return;

    // update world movement
    [self updateWorld];        
}

#pragma mark - touches

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    if(_hasBegun)
        return;

    _hasBegun = YES;
    [self updateFlight];
}


#pragma mark - debug

- (void)flightLog
{

#ifdef HERO_FLIGHT_LOG

    CGFloat newHeroX = _hero.position.x - _heroStartPosition.x;;
    CGFloat diffX = newHeroX - _oldHeroX;

    CGFloat newHeroY = _hero.position.y;
    CGFloat diffY = newHeroY - _oldHeroY;

    NSLog(@"oldHeroY:%f, newHeroY:%f, diffY:%f", _oldHeroY, newHeroY, diffY);
    NSLog(@"oldHeroX:%f, newHeroX:%f, diffX:%f\n\n", _oldHeroX, newHeroX, diffX);

    if(diffX > 3.5f)
    {
        //NSLog(@"\t -> frame:%d fast oldHeroY:%f, newHeroY:%f, diffY:%f", _frame, _oldHeroY, newHeroY, diffY);
        NSLog(@"\t -> frame:%d fast oldHeroX:%f, newHeroX:%f, diffX:%f\n\n", _frame, _oldHeroX, newHeroX, diffX);
    }
    else if(diffX < 3.0f)
    {
        //NSLog(@"\t -> frame:%d fast oldHeroY:%f, newHeroY:%f, diffY:%f", _frame, _oldHeroY, newHeroY, diffY);
        NSLog(@"\t -> frame:%d slow oldHeroX:%f, newHeroX:%f, diffX:%f\n\n", _frame, _oldHeroX, newHeroX, diffX);
    }

    _oldHeroX = newHeroX;
    _oldHeroY = newHeroY;

#endif

}

@end

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日志：

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// no stuttering .. FPS: 60

2016-10-02 17:27:19.164 TestFlight[11009:1774440] oldHeroY:301.666534, newHeroY:301.666534, diffY:0.000000
2016-10-02 17:27:19.165 TestFlight[11009:1774440] oldHeroX:263.002899, newHeroX:266.335968, diffX:3.333069

2016-10-02 17:27:19.181 TestFlight[11009:1774440] oldHeroY:301.666534, newHeroY:301.666534, diffY:0.000000
2016-10-02 17:27:19.182 TestFlight[11009:1774440] oldHeroX:266.335968, newHeroX:269.669067, diffX:3.333099

// stuttering .. FPS: 60

2016-10-02 17:27:24.584 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:302.500031, diffY:0.833344
2016-10-02 17:27:24.585 TestFlight[11009:1774440] oldHeroX:1346.335083, newHeroX:1351.335083, diffX:5.000000

2016-10-02 17:27:24.585 TestFlight[11009:1774440]    -> frame:413 fast oldHeroX:1346.335083, newHeroX:1351.335083, diffX:5.000000

2016-10-02 17:27:24.600 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:300.833344, diffY:-1.666687
2016-10-02 17:27:24.601 TestFlight[11009:1774440] oldHeroX:1351.335083, newHeroX:1353.001709, diffX:1.666626

2016-10-02 17:27:24.601 TestFlight[11009:1774440]    -> frame:414 slow oldHeroX:1351.335083, newHeroX:1353.001709, diffX:1.666626

2016-10-02 17:27:24.617 TestFlight[11009:1774440] oldHeroY:300.833344, newHeroY:301.666687, diffY:0.833344
2016-10-02 17:27:24.618 TestFlight[11009:1774440] oldHeroX:1353.001709, newHeroX:1356.335083, diffX:3.333374

2016-10-02 17:27:24.634 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.634 TestFlight[11009:1774440] oldHeroX:1356.335083, newHeroX:1359.668457, diffX:3.333374

2016-10-02 17:27:24.650 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.651 TestFlight[11009:1774440] oldHeroX:1359.668457, newHeroX:1363.001831, diffX:3.333374

2016-10-02 17:27:24.667 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:302.500031, diffY:0.833344
2016-10-02 17:27:24.668 TestFlight[11009:1774440] oldHeroX:1363.001831, newHeroX:1368.001831, diffX:5.000000

2016-10-02 17:27:24.668 TestFlight[11009:1774440]    -> frame:418 fast oldHeroX:1363.001831, newHeroX:1368.001831, diffX:5.000000

2016-10-02 17:27:24.684 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:300.833344, diffY:-1.666687
2016-10-02 17:27:24.684 TestFlight[11009:1774440] oldHeroX:1368.001831, newHeroX:1369.668457, diffX:1.666626

2016-10-02 17:27:24.685 TestFlight[11009:1774440]    -> frame:419 slow oldHeroX:1368.001831, newHeroX:1369.668457, diffX:1.666626

2016-10-02 17:27:24.700 TestFlight[11009:1774440] oldHeroY:300.833344, newHeroY:301.666687, diffY:0.833344
2016-10-02 17:27:24.701 TestFlight[11009:1774440] oldHeroX:1369.668457, newHeroX:1373.001831, diffX:3.333374

2016-10-02 17:27:24.717 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:302.500031, diffY:0.833344
2016-10-02 17:27:24.718 TestFlight[11009:1774440] oldHeroX:1373.001831, newHeroX:1378.001831, diffX:5.000000

2016-10-02 17:27:24.718 TestFlight[11009:1774440]    -> frame:421 fast oldHeroX:1373.001831, newHeroX:1378.001831, diffX:5.000000

2016-10-02 17:27:24.734 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:301.666687, diffY:-0.833344
2016-10-02 17:27:24.734 TestFlight[11009:1774440] oldHeroX:1378.001831, newHeroX:1381.335205, diffX:3.333374

// no stuttering  .. FPS: 60

2016-10-02 17:27:24.750 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.751 TestFlight[11009:1774440] oldHeroX:1381.335205, newHeroX:1384.668579, diffX:3.333374

2016-10-02 17:27:24.767 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.768 TestFlight[11009:1774440] oldHeroX:1384.668579, newHeroX:1388.001953, diffX:3.333374

2016-10-02 17:27:24.784 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.784 TestFlight[11009:1774440] oldHeroX:1388.001953, newHeroX:1391.335327, diffX:3.333374

2016-10-02 17:27:24.801 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.801 TestFlight[11009:1774440] oldHeroX:1391.335327, newHeroX:1394.668701, diffX:3.333374

2016-10-02 17:27:24.817 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.818 TestFlight[11009:1774440] oldHeroX:1394.668701, newHeroX:1398.002075, diffX:3.333374

2016-10-02 17:27:24.834 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.834 TestFlight[11009:1774440] oldHeroX:1398.002075, newHeroX:1401.335449, diffX:3.333374

2016-10-02 17:27:24.850 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.851 TestFlight[11009:1774440] oldHeroX:1401.335449, newHeroX:1404.668823, diffX:3.333374

2016-10-02 17:27:24.867 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.868 TestFlight[11009:1774440] oldHeroX:1404.668823, newHeroX:1408.002197, diffX:3.333374

// stuttering  .. FPS: 60

2016-10-02 17:27:24.883 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:300.833344, diffY:-0.833344
2016-10-02 17:27:24.884 TestFlight[11009:1774440] oldHeroX:1408.002197, newHeroX:1409.668823, diffX:1.666626

2016-10-02 17:27:24.885 TestFlight[11009:1774440]    -> frame:431 slow oldHeroX:1408.002197, newHeroX:1409.668823, diffX:1.666626

2016-10-02 17:27:24.901 TestFlight[11009:1774440] oldHeroY:300.833344, newHeroY:302.500031, diffY:1.666687
2016-10-02 17:27:24.902 TestFlight[11009:1774440] oldHeroX:1409.668823, newHeroX:1414.668823, diffX:5.000000

2016-10-02 17:27:24.902 TestFlight[11009:1774440]    -> frame:432 fast oldHeroX:1409.668823, newHeroX:1414.668823, diffX:5.000000

2016-10-02 17:27:24.917 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:300.833344, diffY:-1.666687
2016-10-02 17:27:24.918 TestFlight[11009:1774440] oldHeroX:1414.668823, newHeroX:1416.335449, diffX:1.666626

2016-10-02 17:27:24.918 TestFlight[11009:1774440]    -> frame:433 slow oldHeroX:1414.668823, newHeroX:1416.335449, diffX:1.666626

2016-10-02 17:27:24.934 TestFlight[11009:1774440] oldHeroY:300.833344, newHeroY:302.500031, diffY:1.666687
2016-10-02 17:27:24.935 TestFlight[11009:1774440] oldHeroX:1416.335449, newHeroX:1421.335449, diffX:5.000000

2016-10-02 17:27:24.935 TestFlight[11009:1774440]    -> frame:434 fast oldHeroX:1416.335449, newHeroX:1421.335449, diffX:5.000000

2016-10-02 17:27:24.950 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:301.666687, diffY:-0.833344
2016-10-02 17:27:24.951 TestFlight[11009:1774440] oldHeroX:1421.335449, newHeroX:1424.668823, diffX:3.333374

// no stuttering for a while (17 seconds .. long time) .. FPS: 60

2016-10-02 17:27:24.967 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:24.968 TestFlight[11009:1774440] oldHeroX:1424.668823, newHeroX:1428.002197, diffX:3.333374
.
.
.

2016-10-02 17:27:41.559 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:41.559 TestFlight[11009:1774440] oldHeroX:4742.992188, newHeroX:4746.325684, diffX:3.333496

// stuttering .. FPS: 60 

2016-10-02 17:27:41.575 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:300.833344, diffY:-0.833344
2016-10-02 17:27:41.576 TestFlight[11009:1774440] oldHeroX:4746.325684, newHeroX:4747.992188, diffX:1.666504

2016-10-02 17:27:41.576 TestFlight[11009:1774440]    -> frame:1432 slow oldHeroX:4746.325684, newHeroX:4747.992188, diffX:1.666504

2016-10-02 17:27:41.592 TestFlight[11009:1774440] oldHeroY:300.833344, newHeroY:302.500031, diffY:1.666687
2016-10-02 17:27:41.593 TestFlight[11009:1774440] oldHeroX:4747.992188, newHeroX:4752.992188, diffX:5.000000

2016-10-02 17:27:41.593 TestFlight[11009:1774440]    -> frame:1433 fast oldHeroX:4747.992188, newHeroX:4752.992188, diffX:5.000000

2016-10-02 17:27:41.609 TestFlight[11009:1774440] oldHeroY:302.500031, newHeroY:301.666687, diffY:-0.833344
2016-10-02 17:27:41.609 TestFlight[11009:1774440] oldHeroX:4752.992188, newHeroX:4756.325684, diffX:3.333496

2016-10-02 17:27:41.625 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:41.626 TestFlight[11009:1774440] oldHeroX:4756.325684, newHeroX:4759.659180, diffX:3.333496

2016-10-02 17:27:41.642 TestFlight[11009:1774440] oldHeroY:301.666687, newHeroY:301.666687, diffY:0.000000
2016-10-02 17:27:41.643 TestFlight[11009:1774440] oldHeroX:4759.659180, newHeroX:4762.992676, diffX:3.333496
.
.
.
// and so on ..

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编辑：

我将此添加到addHero:方法中
```
_hero.physicsBody.angularDamping = 0.0f;
```
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我改变了，touchesBegan:这样太空船立即以最大速度飞行而不起飞。
```
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    if(_hasBegun)
        return;

    _hasBegun = YES;
    _hero.physicsBody.velocity = CGVectorMake(kMaxHeroVelocityX, kMaxHeroVelocityY);
}
```
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- 我在没有updateFlying:方法的情况下运行代码。飞船立即以最大速度飞行，无需起飞。它以恒定速度飞行，因此不需要更新速度。
- 我尝试了其他事情，例如将更新放入didSimulatePhysics:.. 打开飞行模式 .. 正如@Confused 建议的那样.. 但没有任何帮助来解决这个问题。正如@crashoverride777 所说，它仍然不是 100% 完美。

我将不胜感激任何其他想法。

Answer 1

Con*_*sed 5

这是因为 SpriteKit 的默认物理和运动/变换处理未按增量时间/增量时间进行校正。相反，每当帧速率由于系统调用或其他中断而下降时，它就会断断续续。这些事情在 iOS 设备上经常发生。iOS 系统会不断检查网络并监控各种后台活动的其他状态，并对收到的信息做出响应。

有两种方法可以处理。

打开飞行模式，关闭所有后台更新应用程序，并严格限制几乎所有应用程序在其设置中执行后台进程；这减少了操作系统噪音和开销。
使用增量时间滚动您自己的调整和补偿机制，这样即使跳过一两帧，事情似乎也会继续以正确的速度移动到预期的目的地。

如果您不限于 SpriteKit，或者不需要它的物理，您可以包含另一个物理引擎并使用它。这最终意味着你可以使用 SceneKit、Core Animation 甚至 Metal 来进行渲染……或者 SpriteKit

两个最明智的选择是 Box2D 和 Chipmunk2D。

这是将 Box2D 添加到 iOS 的教程：https : //www.raywenderlich.com/2061-liquidfun-tutorial-with-metal-and-swift-part-1

这是 Chipmunk2D 的 Swift 包装器：https : //github.com/jakubknejzlik/ChipmunkSwiftWrapper

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