圓弧的碰撞檢測

Question

那麼我如何實現圓弧的碰撞檢測呢？我必須使用Box 2d碰撞還是可以用其他方式使用Rectangle或類似的東西？

順便說一句我討厭box2d，因爲我不明白大部分的東西，所以如果有一個解決方案排除box2d，它將非常感激。

的黃色弧線不斷在黑色圓圈旋轉。我如何在這裏實現碰撞檢測？

請幫忙！謝謝！

Answer 1

要避免使用Box2D的，你可以定義形狀爲多邊形，並使用polygon.contains(x,y)方法或使用Intersector

下面是同時使用的例子：

import com.badlogic.gdx.ApplicationAdapter; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.InputProcessor; 
import com.badlogic.gdx.graphics.Color; 
import com.badlogic.gdx.graphics.GL20; 
import com.badlogic.gdx.graphics.glutils.ShapeRenderer; 
import com.badlogic.gdx.math.Circle; 
import com.badlogic.gdx.math.Intersector; 
import com.badlogic.gdx.math.Polygon; 

public class Test extends ApplicationAdapter implements InputProcessor{ 
    private ShapeRenderer sr; 
    private Polygon polya; 

    private boolean isColliding = false; 
    private Circle mp; 

    @Override 
    public void create() { 

     //define arc as polygon 
     // the more points used to define the shape will 
     // increase both required computation and collision precision 
     polya = new Polygon(); 

    // create vertices 
    float section = 15f; 
    float[] newVerts = new float[200]; 
    for(int i = 0; i < 50; i++){ 
     newVerts[i*2] = (float)Math.sin(i/section); //x 0 to 98 even 
     newVerts[i*2+1] = (float)Math.cos(i/section); //y 1 to 99 odd 

     newVerts[199-i*2] = (float)Math.cos(i/section); //x 100 to 108 
     newVerts[198-i*2] = (float)Math.sin(i/section) + 0.2f; //y 101 to 199 

    } 

    polya.setVertices(newVerts); 
    polya.scale(50); 
    polya.setOrigin(1, 1); 
    polya.rotate(60); 

     //define circle to act as point for checking intersections 
     mp = new Circle(Gdx.graphics.getWidth()/2,Gdx.graphics.getHeight()/2,4); 
     // setup batchers 
     sr = new ShapeRenderer(); 
     sr.setAutoShapeType(true); 

     Gdx.input.setInputProcessor(this); 

    } 

    @Override 
    public void render() { 
     Gdx.gl.glClearColor(0f, 0f, 0f, 0f); 
     Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 

     // check collision with polygon 
     isColliding = polya.contains(mp.x,mp.y); 

     //check collision using Intersector 
     isColliding = Intersector.isPointInPolygon(polya.getTransformedVertices(),0,polya.getVertices().length,mp.x,mp.y); 


     sr.begin(); 
     sr.setColor(Color.WHITE); 
     if(isColliding){ 
      sr.setColor(Color.RED); 
     } 
     sr.polygon(polya.getTransformedVertices()); 
     sr.circle(mp.x,mp.y,mp.radius); 
     sr.end(); 

    } 

    @Override 
    public void dispose() { 
    } 

    @Override 
    public boolean mouseMoved(int screenX, int screenY) { 
     int newy = Gdx.graphics.getHeight() - screenY; 
     polya.setPosition(screenX, newy); 
     return false; 
    } 


    (... removed unused input processor methods for clarity ...) 
}