java - 矩形碰撞检测算法半工作

Question

我正在用 slick2d + java 编写碰撞检测算法，我最终将在我将要制作的平台游戏中使用它。该算法的工作原理是检测玩家与矩形的重叠程度，然后通过重叠将玩家移出矩形。问题是，该算法有很多问题我不知道如何解决。首先，有时玩家会移出矩形太远，因此看起来像是在弹跳。其次，有时玩家能够在矩形内移动很小但很明显的距离。最后，如果我提高速度，有时玩家可以一直穿过矩形。这是一个非常模糊的问题，但我真的需要一些帮助来找出问题所在。任何想法都将不胜感激。如果您安装了 Slick2D，源代码应该可以毫无问题地编译。

算法:

public void Collision(Polygon player, Polygon poly, Vector2f translation){
    Vector2f magnitude = new Vector2f();

    //Find the vectre of each object
    Vector2f p1Centre = new Vector2f(player.getX() + (player.getWidth()/2), player.getY() + (player.getHeight()/2));
    Vector2f p2Centre = new Vector2f(poly.getX() + (poly.getWidth()/2), poly.getY() + (poly.getHeight()/2));

    //Calculate the distance between the two
    Vector2f distance = new Vector2f(p1Centre);
    distance.sub(p2Centre);

    //Get the absolute distance
    Vector2f absDistance = new Vector2f(distance.x<0 ? -distance.x : distance.x, distance.y<0 ? -distance.y : distance.y);

    //Get the combined half widths and heights of each object
    Vector2f halvedBounds = new Vector2f((player.getWidth() + poly.getWidth())/2.0f, (player.getHeight() + poly.getHeight())/2.0f);

    //If the absolute distance is less thate the halved widths heights then there is a collision
    if((absDistance.x < halvedBounds.x) && (absDistance.y < halvedBounds.y)){

        //Set the magnitude vector to the halved bounds minus the absolute distance
        magnitude.x = halvedBounds.x - absDistance.x;
        magnitude.y = halvedBounds.y - absDistance.y;

        //Only react to the lesser overlap;
        if(magnitude.x < magnitude.y){
            magnitude.x = (distance.x > 0) ? magnitude.x : -magnitude.x;
            magnitude.y = 0;
        }
        else{
            magnitude.y = (distance.y > 0) ? magnitude.y : -magnitude.y;
            magnitude.x = 0;
        }

        //Debug
        System.out.println(magnitude.x+"            "+magnitude.y);
        System.out.println(translation.x+"            "+translation.y+"\n");

        //Add the magnitude to the player position
        position.add(magnitude);
    }       
}

完整来源:

import java.util.ArrayList;

import org.newdawn.slick.AppGameContainer;
import org.newdawn.slick.BasicGame;
import org.newdawn.slick.Color;
import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.Input;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.geom.Polygon;
import org.newdawn.slick.geom.Vector2f;

public class TestCode extends BasicGame {

    private Vector2f position = new Vector2f(300, 300);

    private ArrayList<Polygon> solids;
    private Polygon player;

    public TestCode(String title) {
        super(title);
    }

    public static void main(String[] args) throws SlickException{
        AppGameContainer game = new AppGameContainer(new TestCode("test"));
        game.setDisplayMode(800, 600, false);
        game.start();
    }

    @Override
    public void render(GameContainer gc, Graphics g) throws SlickException {

        if(gc.isPaused()){
            g.setColor(Color.red);
            g.drawString("Paused", 90, 10);
        }else{
            g.setColor(Color.green);
            g.drawString("Playing", 90, 10);
        }

        g.setColor(Color.red);
        for(Polygon p : solids)
            g.fill(p);

        g.setColor(Color.cyan);
        g.fill(player);

    }

    @Override
    public void init(GameContainer gc) throws SlickException {      
        gc.setVSync(true);

        solids = new ArrayList<Polygon>();

        player = new Polygon(new float[]{
                50, 50,  // upper left point
                70, 50,  // upper right
                70, 90, // lower right
                50, 90   // lower left
        }); 


        for(int i=0, x=200, y=200; i<10; i++, x+=40){
            solids.add(new Polygon(new float[]{
                    x, y,  // upper left point
                    x+40, y,  // upper right
                    x+40, y+40, // lower right
                    x, y+40   // lower left
            }));    
        }

    }

    @Override
    public void update(GameContainer gc, int delta) throws SlickException {

        Input input = gc. getInput();

        Vector2f translation = new Vector2f(0, 0);

        if(input.isKeyDown(Input.KEY_UP))
            translation.y = -1f;
        if(input.isKeyDown(Input.KEY_DOWN))
            translation.y = 1f;
        if(input.isKeyDown(Input.KEY_LEFT))
            translation.x = -1f;
        if(input.isKeyDown(Input.KEY_RIGHT))
            translation.x = 1f;

        translation.normalise();
        translation.x*=2;
        translation.y*=2;

        position.add(translation);

        for(Polygon p : solids)
            Collision(player, p, translation);

        player.setLocation(position);
    }

    public void Collision(Polygon player, Polygon poly, Vector2f translation){
        Vector2f magnitude = new Vector2f();

        //Find the vectre of each object
        Vector2f p1Centre = new Vector2f(player.getX() + (player.getWidth()/2), player.getY() + (player.getHeight()/2));
        Vector2f p2Centre = new Vector2f(poly.getX() + (poly.getWidth()/2), poly.getY() + (poly.getHeight()/2));

        //Calculate the distance between the two
        Vector2f distance = new Vector2f(p1Centre);
        distance.sub(p2Centre);

        //Get the absolute distance
        Vector2f absDistance = new Vector2f(distance.x<0 ? -distance.x : distance.x, distance.y<0 ? -distance.y : distance.y);

        //Get the combined half widths and heights of each object
        Vector2f halvedBounds = new Vector2f((player.getWidth() + poly.getWidth())/2.0f, (player.getHeight() + poly.getHeight())/2.0f);

        //If the absolute distance is less thate the halved widths heights then there is a collision
        if((absDistance.x < halvedBounds.x) && (absDistance.y < halvedBounds.y)){

            //Set the magnitude vector to the halved bounds minus the absolute distance
            magnitude.x = halvedBounds.x - absDistance.x;
            magnitude.y = halvedBounds.y - absDistance.y;

            //Only react to the lesser overlap;
            if(magnitude.x < magnitude.y){
                magnitude.x = (distance.x > 0) ? magnitude.x : -magnitude.x;
                magnitude.y = 0;
            }
            else{
                magnitude.y = (distance.y > 0) ? magnitude.y : -magnitude.y;
                magnitude.x = 0;
            }

            //Debug
            System.out.println(magnitude.x+"            "+magnitude.y);
            System.out.println(translation.x+"            "+translation.y+"\n");

            //Add the magnitude to the player position
            position.add(magnitude);
        }       
    }   
}

Answer 1

高速和玩家穿过矩形的问题与您对碰撞数据进行采样的频率有关。

假设我真的很笨，我每秒只检查一次碰撞。如果一个物体以每秒 15 米的速度移动，并且它的路径上有一个 1 平方米的正方形。如果我在物体距离广场 7 米时检查碰撞，然后一秒钟后，我将完全错过物体穿过广场的情况。

许多碰撞检测库处理此问题的方式是，与常规对象相比，它们更频繁地检查快速移动的对象。发生这种情况时，您的播放器的移动速度有多“快”？