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使用 Cocos2d 和 Box2d 创建了一个示例项目来测试弹跳球。

问题是球没有掉下来，我不知道为什么。设置了重力，质量没问题，但每一步球都保持在相同的位置。

class BouncingBallLayer : CCLayer
{

    int m_screen_width;
    int m_screen_height;
    CCSprite m_ball;
    b2Body m_body;
    b2World m_world;

    public BouncingBallLayer()
    {
        AccelerometerEnabled = false;

        var screen_size = CCDirector.SharedDirector.WinSize;
        m_screen_width = (int) screen_size.Width;
        m_screen_height = (int) screen_size.Height;

        m_ball = new CCSprite("assets/soccer-ball.png");
        m_ball.Position = new CCPoint(m_screen_width / 2, m_screen_height / 2);
        AddChild(m_ball);

        b2Vec2 gravity = new b2Vec2(0.0f, -8.0f);
        m_world = new b2World(gravity);
        m_world.AllowSleep = false;

        b2BodyDef ground_body_def = new b2BodyDef();
        ground_body_def.position.Set(0, 0);

        b2Body ground_body = m_world.CreateBody(ground_body_def);
        b2EdgeShape ground_edge = new b2EdgeShape();
        b2FixtureDef box_shape_def = new b2FixtureDef();
        box_shape_def.shape = ground_edge;

        ground_edge.Set(new b2Vec2(0, 0), new b2Vec2(m_screen_width / Constants.PTM_RATIO, 0));
        ground_body.CreateFixture(box_shape_def);
        ground_edge.Set(new b2Vec2(0, 0), new b2Vec2(0, m_screen_height / Constants.PTM_RATIO));
        ground_body.CreateFixture(box_shape_def);
        ground_edge.Set(new b2Vec2(0, m_screen_height / Constants.PTM_RATIO), new b2Vec2(m_screen_width / Constants.PTM_RATIO, m_screen_height / Constants.PTM_RATIO));
        ground_body.CreateFixture(box_shape_def);
        ground_edge.Set(new b2Vec2(m_screen_width / Constants.PTM_RATIO, m_screen_height / Constants.PTM_RATIO), new b2Vec2(m_screen_width / Constants.PTM_RATIO, 0));
        ground_body.CreateFixture(box_shape_def);

        b2BodyDef ball_body_def = new b2BodyDef();
        ball_body_def.type = b2BodyType.b2_dynamicBody;
        ball_body_def.position.Set(m_screen_width / 2 / Constants.PTM_RATIO, m_screen_height / 2 / Constants.PTM_RATIO);
        ball_body_def.userData = m_ball;
        m_body = m_world.CreateBody(ball_body_def);

        b2CircleShape circle = new b2CircleShape();
        circle.Radius = 26.0f / Constants.PTM_RATIO;

        b2FixtureDef ball_shape_def = new b2FixtureDef();
        ball_shape_def.shape = circle;
        ball_shape_def.density = 1.0f;
        ball_shape_def.friction = 0.2f;
        ball_shape_def.restitution = 0.8f;
        m_body.CreateFixture(ball_shape_def);

        this.Schedule(Tick);
    }


    void Tick(float dt)
    {
        int velocityIterations = 8;
        int positionIterations = 1;

        // Instruct the world to perform a single step of simulation. It is
        // generally best to keep the time step and iterations fixed.
        m_world.Step(dt, velocityIterations, positionIterations);

        //Iterate over the bodies in the physics world
        for (var b = m_world.BodyList; b != null; b = b.Next)
        {
            if (b.UserData != null)
            {
                //Synchronize the AtlasSprites position and rotation with the corresponding body
                var myActor = ((CCNode)b.UserData);
                myActor.PositionX = b.Position.x * Constants.PTM_RATIO;
                myActor.PositionY = b.Position.y * Constants.PTM_RATIO;
                myActor.Rotation = -1 * CCMacros.CCRadiansToDegrees(b.Angle);
            }
        }

    }


    public static CCScene Scene
    {
        get
        {
            // 'scene' is an autorelease object.
            var scene = new CCScene();

            // 'layer' is an autorelease object.
            var layer = new BouncingBallLayer();

            // add layer as a child to scene
            scene.AddChild(layer);

            // return the scene
            return scene;
        }

    }
}

顺便说一句，在调试时我得到以下异常。

'Bounce.vshost.exe' (Managed (v4.0.30319)): 加载'C:\Users\Максим\Projects\games\kicknrun\branches\cocos2d\KickNRun\Bounce\bin\WindowsGL\Debug\Bounce.exe',已加载符号。

'Bounce.vshost.exe'（托管 (v4.0.30319)）：加载 'C:\Users\Максим\Projects\games\kicknrun\branches\cocos2d\KickNRun\Bounce\bin\WindowsGL\Debug\MonoGame.Framework.dll '

'Bounce.vshost.exe' (Managed (v4.0.30319)): 加载'C:\Users\Максим\Projects\games\kicknrun\branches\cocos2d\KickNRun\Bounce\bin\WindowsGL\Debug\cocos2d-xna.dll '

'Bounce.vshost.exe'（托管 (v4.0.30319)）：加载 'C:\Users\Максим\Projects\games\kicknrun\branches\cocos2d\KickNRun\Bounce\bin\WindowsGL\Debug\OpenTK.dll'

OpenTK.dll 中出现了“System.DllNotFoundException”类型的第一次机会异常

OpenTK.dll 中出现了“System.TypeInitializationException”类型的第一次机会异常

OpenTK.dll 中出现了“System.DllNotFoundException”类型的第一次机会异常

MonoGame.Framework.dll 中出现了“System.DllNotFoundException”类型的第一次机会异常

'Bounce.vshost.exe'（托管 (v4.0.30319)）：加载 'C:\Users\Максим\Projects\games\kicknrun\branches\cocos2d\KickNRun\Bounce\bin\WindowsGL\Debug\box2d.dll'

mscorlib.dll 中出现了“System.IO.FileNotFoundException”类型的第一次机会异常

MonoGame.Framework.dll 中出现了“Microsoft.Xna.Framework.Content.ContentLoadException”类型的第一次机会异常

尽管这些 DLL 已加载。

好的！我终于构建了所有 Cocos2d-xna 东西的调试版本！似乎当世界初始化时，m_flags = b2WorldFlags.e_clearForces。这导致所有运动被重置！还得想办法解决这个问题！

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1 回答 1

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您应该采取以下步骤：

1：在此行之前的tick方法中放置一个CCLogvar myActor = ((CCNode)b.UserData);
这将确定代码是否真的到达了将球定位到b2body的位置。

2：如果控制台显示CCLog，则表示您的位置计算错误，或者您没有正确检索用户数据。

如果 CCLog 没有显示在控制台中，这意味着你没有正确地从世界中检索你的身体。

于 2013-09-19T12:35:45.997 回答