ios - Sprite 套件 - Spring 接头(减震器)

Question

首先，感谢@Smick 提供此处发布的初始车辆代码: Sprite Kit pin joints appear to have an incorrect anchor

我正在尝试在车轮(左轮)和底盘之间添加一个滑动接头，以及一个 Spring 接头，以产生减震效果。

使用下面的代码，我没有得到压缩。我意识到文档显示了一个将两个 bodes 拉在一起的 Spring 接头 - 与我想要的相反。这在 SK 中可能吗？

我认为销接头可能是罪魁祸首？当我注释掉销接头时，汽车零件乱七八糟——一切都在屏幕上飞来飞去。本来，销接头是把轮子固定在底盘上，但显然我想把轮子固定在“避震器”上。

此外，SKPhysicsJointSliding 的“轴”参数让我有些困惑。它需要一个向量。相对于的矢量？

提前谢谢你。

- (SKShapeNode*) makeWheel
{
SKShapeNode *wheel = [[SKShapeNode alloc] init];
CGMutablePathRef myPath = CGPathCreateMutable();
CGPathAddArc(myPath, NULL, 0,0, 16, 0, M_PI*2, YES);
wheel.path = myPath;
wheel.physicsBody.mass = 0.5;
return wheel;
}

- (void) createCar{

// 1. car body
SKSpriteNode *carBody = [SKSpriteNode spriteNodeWithColor:[UIColor whiteColor] size:CGSizeMake(120, 8)];
carBody.position = CGPointMake(200, 700);
carBody.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:carBody.size];
carBody.physicsBody.mass = 1.0;
[self addChild:carBody];

// 2. wheels
SKShapeNode *leftWheel = [self makeWheel];
leftWheel.position = CGPointMake(carBody.position.x - carBody.size.width / 2, carBody.position.y-40);
leftWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:16];
[self addChild:leftWheel];

SKShapeNode *rightWheel = [self makeWheel];
rightWheel.position = CGPointMake(carBody.position.x + carBody.size.width / 2, carBody.position.y);
rightWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:16];
[self addChild:rightWheel];


/* Build left shock absorber and attach wheel */

CGVector av =CGVectorMake(0.0, 5.0);

SKPhysicsJointSliding *leftSlide = [SKPhysicsJointSliding    jointWithBodyA:carBody.physicsBody
                                                                    bodyB:leftWheel.physicsBody
                                                                  anchor:leftWheel.position
                                                                    axis:av];


SKPhysicsJointSpring *leftSpring = [SKPhysicsJointSpring  jointWithBodyA:carBody.physicsBody bodyB:leftWheel.physicsBody
                                                                anchorA:CGPointMake(carBody.position.x - carBody.size.width / 2, carBody.position.y)
                                                            anchorB:leftWheel.position];



SKPhysicsJointPin *leftPin = [SKPhysicsJointPin jointWithBodyA:leftSpring.bodyA
                                                        bodyB:leftSpring.bodyB
                                                        anchor:leftWheel.position];


[self.physicsWorld addJoint:leftSlide];
[self.physicsWorld addJoint:leftSpring];
[self.physicsWorld addJoint:leftPin];

[self.physicsWorld addJoint:[SKPhysicsJointPin jointWithBodyA:carBody.physicsBody     bodyB:rightWheel.physicsBody anchor:rightWheel.position]];

Answer 1

编辑我的答案。悬架需要将车轮连接到滑动体而不是通过滑动接头连接车轮。做前者允许轮子旋转。后者没有。

车辆.m

#import "Vehicle.h"

@implementation Vehicle

- (SKSpriteNode*) makeWheel
{
    SKSpriteNode *wheel = [SKSpriteNode spriteNodeWithImageNamed:@"wheel.png"];
//    wheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:wheel.size.width/2];
    return wheel;
}

-(id)initWithPosition:(CGPoint)pos {

    if (self = [super init]) {

        _joints = [NSMutableArray array];

        int wheelOffsetY    =   60;
        CGFloat damping     =   1;
        CGFloat frequency   =   4;

        SKSpriteNode *chassis = [SKSpriteNode spriteNodeWithColor:[UIColor whiteColor] size:CGSizeMake(120, 8)];
        chassis.position = pos;
        chassis.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:chassis.size];
        [self addChild:chassis];

        _ctop = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(70, 16)];
        _ctop.position = CGPointMake(chassis.position.x+20, chassis.position.y+12);
        _ctop.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_ctop.size];
        [self addChild:_ctop];

        SKPhysicsJointFixed *cJoint = [SKPhysicsJointFixed jointWithBodyA:chassis.physicsBody
                                                                    bodyB:_ctop.physicsBody
                                                                   anchor:CGPointMake(_ctop.position.x, _ctop.position.y)];


        _leftWheel = [self makeWheel];
        _leftWheel.position = CGPointMake(chassis.position.x - chassis.size.width / 2, chassis.position.y - wheelOffsetY);  //Always set position before physicsBody
        _leftWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:_leftWheel.size.width/2];
        _leftWheel.physicsBody.allowsRotation = YES;
        [self addChild:_leftWheel];

        SKSpriteNode *rightWheel = [self makeWheel];
        rightWheel.position = CGPointMake(chassis.position.x + chassis.size.width / 2, chassis.position.y - wheelOffsetY);
        rightWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:rightWheel.size.width/2];
        rightWheel.physicsBody.allowsRotation = YES;
        [self addChild:rightWheel];

//------------- LEFT SUSPENSION ----------------------------------------------------------------------------------------------- //

        SKSpriteNode *leftShockPost = [SKSpriteNode spriteNodeWithColor:[UIColor blueColor] size:CGSizeMake(7, wheelOffsetY)];
        leftShockPost.position = CGPointMake(chassis.position.x - chassis.size.width / 2, chassis.position.y - leftShockPost.size.height/2);
        leftShockPost.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:leftShockPost.size];
        [self addChild:leftShockPost];

       SKPhysicsJointSliding  *leftSlide = [SKPhysicsJointSliding jointWithBodyA:chassis.physicsBody
                                                                           bodyB:leftShockPost.physicsBody
                                                    anchor:CGPointMake(leftShockPost.position.x, leftShockPost.position.y)
                                                      axis:CGVectorMake(0, 1)];

        leftSlide.shouldEnableLimits = TRUE;
        leftSlide.lowerDistanceLimit = 5;
        leftSlide.upperDistanceLimit = wheelOffsetY;


        SKPhysicsJointSpring *leftSpring = [SKPhysicsJointSpring jointWithBodyA:chassis.physicsBody bodyB:_leftWheel.physicsBody
                                                                        anchorA:CGPointMake(chassis.position.x - chassis.size.width / 2, chassis.position.y)
                                                                        anchorB:_leftWheel.position];
        leftSpring.damping = damping;
        leftSpring.frequency = frequency;

        SKPhysicsJointPin *lPin = [SKPhysicsJointPin jointWithBodyA:leftShockPost.physicsBody bodyB:_leftWheel.physicsBody anchor:_leftWheel.position];


//------------- RIGHT SUSPENSION ----------------------------------------------------------------------------------------------- //

        SKSpriteNode *rightShockPost = [SKSpriteNode spriteNodeWithColor:[UIColor blueColor] size:CGSizeMake(7, wheelOffsetY)];
        rightShockPost.position = CGPointMake(chassis.position.x + chassis.size.width / 2, chassis.position.y - rightShockPost.size.height/2);
        rightShockPost.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:rightShockPost.size];
        [self addChild:rightShockPost];

        SKPhysicsJointSliding  *rightSlide = [SKPhysicsJointSliding jointWithBodyA:chassis.physicsBody
                                                                            bodyB:rightShockPost.physicsBody
                                                                           anchor:CGPointMake(rightShockPost.position.x, rightShockPost.position.y)
                                                                             axis:CGVectorMake(0, 1)];

        rightSlide.shouldEnableLimits = TRUE;
        rightSlide.lowerDistanceLimit = 5;
        rightSlide.upperDistanceLimit = wheelOffsetY;


        SKPhysicsJointSpring *rightSpring = [SKPhysicsJointSpring jointWithBodyA:chassis.physicsBody bodyB:rightWheel.physicsBody
                                                                        anchorA:CGPointMake(chassis.position.x + chassis.size.width / 2, chassis.position.y)
                                                                        anchorB:rightWheel.position];
        rightSpring.damping = damping;
        rightSpring.frequency = frequency;

        SKPhysicsJointPin *rPin = [SKPhysicsJointPin jointWithBodyA:rightShockPost.physicsBody bodyB:rightWheel.physicsBody anchor:rightWheel.position];


        // Add all joints to the array.

        [_joints addObject:cJoint];

        [_joints addObject:leftSlide];
        [_joints addObject:leftSpring];
        [_joints addObject:lPin];

        [_joints addObject:rightSlide];
        [_joints addObject:rightSpring];
        [_joints addObject:rPin];

    }

    return self;
}


@end