libgdx box2d摩擦接頭不能正常工作

Question

我想用box2d的摩擦接頭做一個簡單的例子。我創建了一個可以用鼠標或箭頭鍵控制的圓圈。還有一個盒子是用來圈選的。問題是，當我推箱子時，它一直在運動。我添加了一個輔助靜態盒子，這樣我就可以用摩擦接頭將兩個盒子連接起來，以模擬自上而下的摩擦。但它不起作用。這是代碼。

public class MyGdxGame extends ApplicationAdapter { 

    Camera camera; 
    int windowWidth, windowHeight; 

    World physicsWorld; 
    Box2DDebugRenderer debugRenderer; 

    Body frictionerBox; 

    Body boxBody; 
    Body circleBody; 

    @Override 
    public void create() { 
     camera = new OrthographicCamera(2, 2); 

     Box2D.init(); 
     physicsWorld = new World(new Vector2(0, 0), true); 
     debugRenderer = new Box2DDebugRenderer(); 

     // frictioner box 
     BodyDef bDef = new BodyDef(); 
     bDef.type = BodyDef.BodyType.StaticBody; 
     bDef.position.set(0, 0); 
     frictionerBox = physicsWorld.createBody(bDef); 
     PolygonShape fShape = new PolygonShape(); 
     fShape.setAsBox(10, 10); 
     FixtureDef fixDef = new FixtureDef(); 
     fixDef.shape = fShape; 
     fixDef.density = 1.f; 
     fixDef.friction = 1.f; 
     //Fixture fix = 
      frictionerBox.createFixture(fixDef); 

     // box 
     bDef = new BodyDef(); 
     bDef.type = BodyDef.BodyType.DynamicBody; 
     bDef.position.set(0, 50); 
     boxBody = physicsWorld.createBody(bDef); 
     PolygonShape bShape = new PolygonShape(); 
     bShape.setAsBox(25, 25); 
     fixDef = new FixtureDef(); 
     fixDef.shape = bShape; 
     fixDef.density = 1.f; 
     fixDef.friction = 1.f; 
     boxBody.createFixture(fixDef); 

     // circle 
     BodyDef cDef = new BodyDef(); 
     cDef.type = BodyDef.BodyType.DynamicBody; 
     cDef.position.set(20, 20); 
     circleBody = physicsWorld.createBody(cDef); 
     CircleShape cShape = new CircleShape(); 
     cShape.setRadius(12); 
     fixDef = new FixtureDef(); 
     fixDef.shape = cShape; 
     fixDef.density = 1.f; 
     circleBody.createFixture(fixDef); 

     FrictionJointDef frictionJointDef = new FrictionJointDef(); 
     frictionJointDef.maxForce = 10; 
     frictionJointDef.maxTorque = 10; 
     frictionJointDef.initialize(frictionerBox, boxBody, new Vector2(0, 0)); 
     physicsWorld.createJoint(frictionJointDef); 

     bShape.dispose(); 
     cShape.dispose(); 
     fShape.dispose(); 
    } 

    @Override 
    public void render() {  

     handleInput(); 

     physicsWorld.step(Gdx.graphics.getDeltaTime(), 6, 2); 


     Gdx.gl.glClearColor(0.2f, 0.2f, 0.2f, 1); 
     Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 

     debugRenderer.render(physicsWorld, camera.combined); 

    } 


    @Override 
    public void resize(int width, int height) 
    { 
     camera.viewportWidth = width; 
     camera.viewportHeight = height; 
     camera.update(); 
     windowWidth = width; 
     windowHeight = height; 
     System.out.println("resized"); 
    } 

    private void handleInput() 
    { 
     final float ARROW_SPEED = 60.0f; 
     final float MAX_SPEED = 200.f; 
     final float MIN_SPEED = 20.f; 
     float vx, vy; 
     if(Gdx.input.isTouched() || Gdx.input.isButtonPressed(Input.Buttons.LEFT)) 
     { 
      int tx = (Gdx.input.getX() - windowWidth/2); 
      int ty = -Gdx.input.getY() + windowHeight/2; 
      float cx = camera.position.x; 
      float cy = camera.position.y; 
      float px = circleBody.getPosition().x; 
      float py = circleBody.getPosition().y; 
      px = px - cx; 
      py = py - cy; 
      vx = tx - px; 
      vy = ty - py; 
      float speed = (float) Math.sqrt(vx*vx + vy*vy); 
      if(speed > MAX_SPEED) 
      { 
       vx = (vx/speed) * MAX_SPEED; 
       vy = (vy/speed) * MAX_SPEED; 
      } 
      if(speed > 0 && speed < MIN_SPEED) 
      { 
       vx = (vx/speed) * MIN_SPEED; 
       vy = (vy/speed) * MIN_SPEED; 
      } 
     } 

     else 
     { 
      vx = vy = 0; 
      if(Gdx.input.isKeyPressed(Input.Keys.W)) 
      { 
       vy += 1; 
      } 
      if(Gdx.input.isKeyPressed(Input.Keys.S)) 
      { 
       vy -= 1; 
      } 
      if(Gdx.input.isKeyPressed(Input.Keys.A)) 
      { 
       vx -= 1; 
      } 
      if(Gdx.input.isKeyPressed(Input.Keys.D)) 
      { 
       vx += 1; 
      } 
      float speed = (float) Math.sqrt(vx*vx + vy*vy); 
      if(speed > 0.f) 
      { 
       vx = (vx/speed) * ARROW_SPEED; 
       vy = (vy/speed) * ARROW_SPEED; 
      } 
     } 

     circleBody.setLinearVelocity(vx, vy); 

    } 

} 

我在做什麼錯？

Answer 1

我想通了。似乎摩擦是顯而易見的，你必須設置非常高的值爲maxForce和maxTorque。

frictionJointDef.maxForce = 1000000; 
frictionJointDef.maxTorque = 10000000;