java - 弹跳球的物理学

Question

这是问这个问题的正确网站吗，因为我现在已经两次被推荐到另一个网站。

我正在尝试创建具有逼真的物理特性的弹跳球。此刻，当球相互撞击时，它们会朝原来的方向弹回，现在，我在互联网上搜索了如何做到这一点，但我只找到了关于如何检测碰撞的信息，而不是什么之后做。我对物理了解不多，在我能够做到这一点之前我应该​​先学习他们的主题吗？这是我想象球在现实生活中会如何弹跳的图像。这是它的工作原理吗？

_{(来源:thewombatguru.nl)}

此外，我的代码中是否存在不良做法？ (可能，但我学到了很多东西而且我喜欢它)

这是我当前的代码:

小行星.java

package Asteroids;

import javax.swing.*;

public class Asteroids {

    public static void createAndShowGui() {
        GamePanel gamePanel = new GamePanel();
        JFrame frame = new JFrame("Asteroids");
        frame.getContentPane().add(gamePanel);
        frame.pack();
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setLocation(2000, 50);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }

}

GamePanel.java

package Asteroids;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

public class GamePanel extends JPanel implements ActionListener {

    private final int WIDTH = 1000;
    private final int HEIGHT = 1000;

    Timer animationTimer;

    ArrayList<Rock> rocks;

    public GamePanel() {
        Dimension preferredDimension = new Dimension(WIDTH, HEIGHT);
        setPreferredSize(preferredDimension);

        animationTimer = new Timer(10, this);

        setUp();
    }

    public void setUp() {

        rocks = new ArrayList<>();

        rocks.add(new Rock(475, 1000, 0, -1));
        rocks.add(new Rock(0, 500, 1, 0));
        //rocks.add(new Rock(300, 270, -2, 2));
        //rocks.add(new Rock(400, 315, -5, -1));

        animationTimer.start();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        repaint();

        for (Rock rock : rocks) {
            for (Rock rockToCheck : rocks) {
                if (!rock.equals(rockToCheck)) {
                    rock.checkForCollisionWithRocks(rockToCheck);
                }
            }
            rock.checkForCollisionWithFrame(WIDTH, HEIGHT);
            rock.setxPos(rock.getxPos() + rock.getxVelocity());
            rock.setyPos(rock.getyPos() + rock.getyVelocity());
        }
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g.create();

        RenderingHints mainRenderingHints = new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setRenderingHints(mainRenderingHints);

        for (Rock rock : rocks) {
            rock.display(g2d);
        }

        g2d.dispose();
    }
}

Rock.java

package Asteroids;

import java.awt.*;

public class Rock {

    private int xPos;
    private int yPos;
    private int rockWidth;
    private int rockHeight;
    private int xVelocity;
    private int yVelocity;
    private int rockRadius;
    private Color rockColor;

    public Rock(int xPos, int yPos, int xVelocity, int yVelocity) {
        this.xPos = xPos;
        this.yPos = yPos;
        this.xVelocity = xVelocity;
        this.yVelocity = yVelocity;
        rockWidth = 50;
        rockHeight = rockWidth;
        rockRadius = rockWidth / 2;
        rockColor = new Color((int) (Math.random() * 255),(int) (Math.random() * 255),(int) (Math.random() * 255));
    }

    public void setxPos(int xPos) {
        this.xPos = xPos;
    }
    public int getxPos() {
        return xPos;
    }
    public int getRockWidth() {
        return rockWidth;
    }
    public void setRockWidth(int rockWidth) {
        this.rockWidth = rockWidth;
    }
    public int getRockHeight() {
        return rockHeight;
    }
    public void setRockHeight(int rockHeight) {
        this.rockHeight = rockHeight;
    }
    public int getyPos() {
        return yPos;
    }
    public void setyPos(int yPos) {
        this.yPos = yPos;
    }
    public int getxVelocity() {
        return xVelocity;
    }
    public void setxVelocity(int xVelocity) {
        this.xVelocity = xVelocity;
    }
    public int getyVelocity() {
        return yVelocity;
    }
    public void setyVelocity(int yVelocity) {
        this.yVelocity = yVelocity;
    }
    public int getRockRadius() {
        return rockRadius;
    }
    public void setRockRadius(int rockRadius) {
        this.rockRadius = rockRadius;
    }

    public void checkForCollisionWithRocks(Rock rock) {
        int radiusOfBoth = rock.getRockRadius() + rockRadius;
        int horDistance = Math.abs((rock.getxPos() + rock.getRockRadius()) - (xPos + rockRadius));
        int verDistance = Math.abs((rock.getyPos() + rock.getRockRadius()) - (yPos + rockRadius));
        int diagDistance = (int) Math.sqrt(Math.pow(horDistance, 2) + Math.pow(verDistance, 2));

        if (diagDistance <= radiusOfBoth) {

            xVelocity = -xVelocity;
            yVelocity = -yVelocity;

            rock.setxVelocity(-rock.getxVelocity());
            rock.setyVelocity(-rock.getyVelocity());
            rock.setxPos(rock.getxPos() + rock.getxVelocity());
            rock.setyPos(rock.getyPos() + rock.getyVelocity());
        }
    }

    public void checkForCollisionWithFrame(final int WIDTH, final int HEIGHT) {
        if (xPos < 0) {
            xVelocity *= -1;
            xPos = 0;
        } else if (xPos + rockWidth > WIDTH) {
            xVelocity *= -1;
            xPos = WIDTH - rockWidth;
        }

        if (yPos < 0) {
            yVelocity *= -1;
            yPos = 0;
        } else if (yPos + rockHeight > HEIGHT) {
            yVelocity *= -1;
            yPos = HEIGHT - rockHeight;
        }
    }

    public void display(Graphics2D g2d) {
        g2d.setColor(rockColor);
        g2d.fillOval(xPos, yPos, rockWidth, rockHeight);
    }

}

有人能帮忙吗？

Answer 1

您可以从动量守恒定律开始。当两个物体碰撞时总动量不会改变，可以用this link在尝试预测两个物体碰撞后的轨迹时了解背后的计算。

至于您的代码，您似乎在 Rock.java 中缺少一个关键字段 mass。您需要质量来计算物体的动量，稍后您将使用它来预测物体碰撞后的轨迹。

编辑:请注意，链接中的示例在某种程度上仅限于 2 个方向，在这些方向中，对象相互碰撞，它们之间的角度为 180*。然而，通过将动量/速度 vector 分解为 0、90、180、270 度的 4 个方向，在碰撞后概括和找到物体的速度并不难。您必须使用 vector 数学来表示给定对象在 4 个方向上的速度。