XNA - 傍克隆 - 反思球时撞到墙？ [英] XNA - Pong Clone - Reflecting ball when it hits a wall?

问题描述

我试图让球反弹了我的用户界面的顶部和底部的'墙'创建2D傍克隆时的感觉。
这是我的Game.cs

I'm trying to make the ball bounce off of the top and bottom 'Walls' of my UI when creating a 2D Pong Clone. This is my Game.cs

public void CheckBallPosition()
{
    if (ball.Position.Y == 0 || ball.Position.Y >= graphics.PreferredBackBufferHeight)
        ball.Move(true);
    else
        ball.Move(false);

    if (ball.Position.X < 0 || ball.Position.X >= graphics.PreferredBackBufferWidth)
        ball.Reset();
}

目前，我在我的Ball.cs

At the moment I'm using this in my Ball.cs

    public void Move(bool IsCollidingWithWall)
    {
        if (IsCollidingWithWall)
        {
            Vector2 normal = new Vector2(0, 1);
            Direction = Vector2.Reflect(Direction,normal);
            this.Position += Direction;
            Console.WriteLine("WALL COLLISION");
        }
        else
            this.Position += Direction;
    }

它的工作原理，但我使用的是手动输入正常和我想知道如何计算正常屏幕？

推荐答案

好了，这是我将如何处理它

Well, this is how I would handle it

public void CheckBallPositionAndMove()
{
    if (ball.Position.Y <= 0 || ball.Position.Y >= graphics.PreferredBackBufferHeight)
        ball.HandleWallCollision();

    ball.Move();

    if (ball.Position.X < 0 || ball.Position.X >= graphics.PreferredBackBufferWidth)
        ball.Reset();
}

//In Ball.cs:
private void HandleWallCollision(Vector2 normal)
{
    Direction.Y *= -1; //Reflection about either normal is the same as multiplying y-vector by -1
}

private void Move()
{
    this.Position += Direction;
}

---

然而，使用这种

请注意离散碰撞检测，你等到球已经移过顶后/屏幕下方来检测碰撞; 发生帧之间的碰撞可能是noticably关，尤其是当球快速移动。这是尤其的一个问题，如果你正在使用这种碰撞检测方法检测碰撞桨，因为如果球移动速度不够快，这是可能的球通过桨向右移动！

---

Note however that using this "discrete" collision detection, you wait until after the ball has moved past the top/bottom of the screen to detect a collision; collisions that occur "between" frames may be noticably off, especially if the ball is moving fast. This is especially a problem if you are using this collision-detection method to detect collision with a paddle, since, if the ball is moving fast enough, it is possible for the ball to move right through the paddle!

对这个问题的解决方法是使用了被称为连续碰撞检测。 CCD通常比显著离散的碰撞检测更加复杂;幸运的是，乒乓球是很简单的，这样做CCD只会稍微复杂一些。不过，你仍然会需要高中代数扎实抓好以求解方程。

The solution to this problem is to use what is known as Continuous Collision Detection. CCD is usually significantly more complex than discrete collision detection; fortunately, pong is simple enough that doing CCD would only be slightly more complex. However, you'd still need a solid grasp of high-school algebra to solve the equations.

如果你仍然有兴趣，有CCD的一个很好的解释在< A HREF =http://www.cs.unc.edu/%7Elin/COMP259-S05/LEC/14.ppt相对=nofollow>这个讲座和的这个GameDev文章去多一点深入。也有许多的问题与它左右。

If you are still interested, there is a good explaination of CCD in this lecture, and this GameDev article goes a bit more in-depth. There are also many questions relating to it on SO.

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