Question

我正在玩CocosSharp中的box2d。我确实有一个问题 - 对象移动得太慢了！尽管价值很高......

// Physics
    public const float GRAVITY = -99999999999999999999999999999f;
    public const int PTM = 32;
    public const float ROCKET_MASS = 10000f;
    public const float TIMESTEP = 1f/240f;

请注意，我已经改变了时间步。我试图使用质量，但它完全没有意义！

// Add rocket's physics
        var def = new b2BodyDef ();
        def.allowSleep = true;
        def.position = new b2Vec2(0.0f, 0.0f);
        def.type = b2BodyType.b2_dynamicBody;

        body = world.CreateBody (def);
        // body.Mass = Globals.ROCKET_MASS;
        body.SetActive(true);

        b2PolygonShape bodyBox = new b2PolygonShape();
        bodyBox.SetAsBox(0.1f , 0.5f);  // !

        b2FixtureDef bodyFixture = new b2FixtureDef();
        bodyFixture.shape = bodyBox;
        bodyFixture.density = 0.5f;
        bodyFixture.friction = 0.4f;

        body.CreateFixture(bodyFixture);

以下是我初始化物理的方法：

void InitPhysics ()
    {
        // Init the world
        var gravity = new b2Vec2 (0.0f, Globals.GRAVITY);
        world = new b2World (gravity);

        world.SetAllowSleeping (true);
        world.SetContinuousPhysics (true);

        // Now init the ground
        new Ground(world);
    }

这是我的渲染器代码：

private void StartScheduling()
    {
        Schedule(t =>
            {
                if(t <= Globals.TIMESTEP)
                    timeAccumulator += t;
                else
                    timeAccumulator += Globals.TIMESTEP; 

                while (timeAccumulator >= Globals.TIMESTEP)
                {
                    world.Step(Globals.TIMESTEP, 6, 2);
                    timeAccumulator -= Globals.TIMESTEP;

                    // If touched, then do apply force
                    if (touch)
                    {
                        rocket.body.ApplyLinearImpulse(new b2Vec2(0f, 10000f), b2Vec2.Zero);
                    }

                    world.DrawDebugData();

                    rocket.UpdateRocketPosition();
                }

                world.ClearForces();
            });
    }

我好累，请帮忙！火箭必须快速下降，但事实并非如此！

Answer 1

感谢@ iforce2d。

解决方案是在将结果渲染到屏幕时使用PTM调整box2d单位。至于我，我不明白，box2d世界是一个非常小的东西，并不依赖于设备的屏幕尺寸，我应该将它（放大）用于渲染。现在它的效果非常好：

public void UpdateRocketPosition ()
    {
        // PositionX, Y are sprite's positions
        PositionX = body.Position.x * Globals.PTM;
        PositionY = body.Position.y * Globals.PTM;
    }

尽管在box2d中有巨大的重力，但运动速度太慢

1 个答案: