浮力模拟

Question

我正在尝试模拟Android应用程序的2D对象上的浮力行为，没有涉及摩擦。有些东西不能正常工作：“弹跳”的高度以不规则的方式变化，我认为错误应该在速度的更新中，但我不确定。

任何人都可以在我的代码中看到错误吗？

public class MainActivity extends Activity {

    Semaphore moveSemaphore = new Semaphore(1);
    static WindowManager.LayoutParams params;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        params = new WindowManager.LayoutParams( 80, 80,
                WindowManager.LayoutParams.TYPE_APPLICATION,
                WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,
                PixelFormat.TRANSPARENT);

        final BallView ball = new BallView(this);
        addContentView(ball, params);
        ball.setX(100);
        ball.setY(50);

        final Thread move = new Thread(new Runnable(){
            double speed = 0;
            double G = 9;
            double fullBuoyancy = -G * 10;
            double prevtime = System.currentTimeMillis();
            double elapsed;

            double fluidstart = 300;
            double objectHeight = 100;
            double currPosy = 50;
            double p;

            @Override
            public void run() {

                while(true){

                    try {
                        moveSemaphore.acquire();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            double currDepth = 0;
                            long currtime = System.currentTimeMillis();
                            elapsed = (currtime - prevtime) * 0.01;
                            prevtime = currtime;
                            currPosy = ball.getY();

                            // COMPUTE HOW MUCH OF THE BALL IS INSIDE OF THE FLUID
                            if (currPosy > (fluidstart + objectHeight/2)){
                                currDepth = objectHeight;
                            } else if (currPosy > (fluidstart - objectHeight/2)) {
                                currDepth = currPosy - fluidstart;
                            }


                            p = currDepth / objectHeight; // PERCENTAGE OF THE FULL BUOYANT FORCE TO BE APPLIED
                            speed = speed + (G + fullBuoyancy * p) * elapsed;

                            currPosy += speed * elapsed;
                            ball.setY((float)currPosy);

                            moveSemaphore.release();
                        }
                    });
                }
            }
        });

        move.start();
    }
}

Answer 1

if语句逻辑不正确。

double emerge = fluidstart - (currPosy - (objectHeight / 2));
if (emerge <= 0) { // complete submersion
   currDepth = objectHeight;
} else {
   currDepth = objectHeight - emerge;
}

Answer 2

问题出在if语句中，这是正确的解决方案：

if (currPosy > (fluidstart + objectHeight/2)){//complete submersion
    currDepth = objectHeight;
} else if (currPosy > (fluidstart - objectHeight/2)) {//partial submersion
    currDepth = (currPosy + objectHeight/2) - fluidstart;
}