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我正在使用 Box2D 在 Cocos2d 中开发游戏。目前我已经建立了一个有一些界限的系统。他们是为了一个球。我希望流星从屏幕外进入并击打球。

边界在我的 init 方法中定义如下：

    // Define the ground body.
    b2BodyDef groundBodyDef;
    groundBodyDef.type = b2_staticBody;
    groundBodyDef.position.Set(0, 0); // bottom-left corner

    // Call the body factory which allocates memory for the ground body
    // from a pool and creates the ground box shape (also from a pool).
    // The body is also added to the world.
    b2Body* groundBody = world->CreateBody(&groundBodyDef);

    // Define the ground box shape.
    b2PolygonShape groundBox;       

    // bottom
    groundBox.SetAsEdge(b2Vec2(0,0), b2Vec2(screenSize.width/PTM_RATIO,0));
    groundBody->CreateFixture(&groundBox,0);

    // top
    groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,0);

    // left
    groundBox.SetAsEdge(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(0,0));
    groundBody->CreateFixture(&groundBox,0);

    // right
    groundBox.SetAsEdge(b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,0));
    groundBody->CreateFixture(&groundBox,0);

    //Collision filter stuff here. Not working.
    b2Filter filter;
    filter.groupIndex = -2;
    groundBody->GetFixtureList()[0].SetFilterData(filter);

我的球定义如下：

    //Physics object.
    b2BodyDef ballBodyDef;
    ballBodyDef.position.Set(ball.position.x/PTM_RATIO, ball.position.y/PTM_RATIO);
    ballBodyDef.type = b2_dynamicBody;
    ballBodyDef.userData = ball;
    ballBodyDef.bullet = true;
    ballBody = world->CreateBody(&ballBodyDef);

    b2CircleShape ballShape;
    ballShape.m_radius = 10.0/PTM_RATIO;
    b2FixtureDef ballFix;
    ballFix.restitution = 1.1f;
    ballFix.density  = 0.0f;
    ballFix.shape = &ballShape;
    ballBody->CreateFixture(&ballFix);

流星是用两种方法制作的，较短的方法是放置流星。较长的人实际上使用较短的人给出的点来创建它们：

-(void)createMeteorAtPoint:(CGPoint)point {
    //Create particle sprite representation.
    CCParticleMeteor *meteor = [[CCParticleMeteor alloc] initWithTotalParticles:200];
    meteor.gravity = ccp(-200,0);
    meteor.life = 0.5;
    meteor.lifeVar = 0.25;
    meteor.position = point;
    meteor.tag = 2;
    meteor.startSize = 5.0;
    meteor.startSizeVar = 3.0;
    [self addChild:meteor];

    //Make meteor physics body.    
    b2BodyDef meteorBodyDef;
    meteorBodyDef.position.Set(point.x/PTM_RATIO, point.y/PTM_RATIO);
    meteorBodyDef.type = b2_dynamicBody;
    meteorBodyDef.userData = meteor;
    b2Body *meteorBody = world->CreateBody(&meteorBodyDef);
    meteorBody->SetBullet(true);

    b2CircleShape meteorShape;
    meteorShape.m_radius = 7.5/PTM_RATIO;
    b2FixtureDef meteorFix;
    meteorFix.shape = &meteorShape;
    meteorFix.density = 1;

    //Give it the same negative group index of the boundaries to prevent collision.
    //Not working.
    meteorFix.filter.groupIndex = -2;

    meteorBody->CreateFixture(&meteorFix);

    //Give it a motion.
    b2Vec2 F;
    F.Set(CCRANDOM_0_1()*2, 0);
    meteorBody->SetLinearVelocity(F);
}

//Create a bunch of meteors that will sweep from left to right.
-(void)createMeteors {
    for (int i = 0; i < 8*40; i += 20) {
        [self createMeteorAtPoint:ccp(-40.0f, i + 2)];
    }
    NSLog(@"HERE");
}

我可以看到物理对象堆积在屏幕的一侧，因为我设置了调试标志。但是一个：尽管是相同的负组指数，但他们并没有越过边界。第二：球决定它不喜欢右边的墙，然后穿过它。

如果你认为我遗漏了一些重要的东西，请告诉我。

4

1 回答 1

1

只有一个边界装置的组索引为 -2（底部）。您可以像这样遍历身体的所有固定装置：

for (b2Fixture* f = body->GetFixtureList(); f; f = f->GetNext())
{
    //do something with the fixture 'f'
    f->SetFilterData(...);
}

我不确定为什么球会忽略任何墙壁（除非你通过在球和墙壁所属的地面之间创建鼠标关节来移动它，并且关节设置为不碰撞连接的物体.. . 但在这种情况下，球将忽略所有墙壁，并且仅在移动时）。

于 2012-09-15T00:19:17.210 回答