LibGDX + Box2D旋轉

Question

如何使用LibGDX在Box2D中應用自動旋轉（如在現實世界中）？這看起來並不現實（見下圖）。

在現實世界中，該塊會旋轉並摔倒，但他們沒有在這個模擬。

世界已經Ÿ重力在-9.81（14:25和碰撞優良工程）這是代碼，我在那裏創建框：

PolygonShape pShape = new PolygonShape(); 
FixtureDef fDef = new FixtureDef(); 
BodyDef bDef = new BodyDef(); 
Body body; 

pShape.setAsBox(width, height); 
bDef.position.set(x, y); 
bDef.type = type; 
fDef.shape = pShape; 
fDef.density = 1.0f; 
fDef.friction = 0.3f; 
body = world.createBody(bDef); 
body.createFixture(fDef); 
body.setUserData(this); 
MassData md = new MassData(); 
md.mass = 5; 
body.setMassData(md); 

代碼主遊戲類：

public class Game implements ApplicationListener { 

public static int WIDTH; 
public static int HEIGHT; 

World world; 
Box2DDebugRenderer dr; 
OrthographicCamera cam; 
float time; 
final float P = 1/60f; 
final static int C = 100; 

public void create() { 
    Gdx.gl.glClearColor(.1f, .1f, .1f, 1.0f); 
    WIDTH = Gdx.graphics.getWidth(); 
    HEIGHT = Gdx.graphics.getHeight(); 
    world = new World(new Vector2(0, -9.8f), false); 

    dr = new Box2DDebugRenderer(); 
    cam = new OrthographicCamera(); 
    cam.setToOrtho(false, WIDTH/C, HEIGHT/C); 

    new Block(world, BodyType.StaticBody, 2,  HEIGHT,  0,   HEIGHT); 
    new Block(world, BodyType.StaticBody, 2,  HEIGHT,  WIDTH-40, HEIGHT); 
    new Block(world, BodyType.StaticBody, WIDTH, 2,   WIDTH,  HEIGHT); 
    new Block(world, BodyType.StaticBody, WIDTH, 2,   WIDTH,  0); 
} 

public void render() { 
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 
    input(); 

    dr.render(world, cam.combined); 

    time += Gdx.graphics.getDeltaTime(); 
    while(time >= P) { 
     update(); 
     time -= P; 
    } 
} 

public void update() { 
    world.step(P, 5, 5); 
} 

public void input() { 
    if(Gdx.input.isTouched()) { 
     new Block(world, BodyType.DynamicBody, 50, 20, Gdx.input.getX(), HEIGHT-Gdx.input.getY()); 
    } 
} 

public void dispose() { } 
public void pause() { } 
public void resize(int arg0, int arg1) { } 
public void resume() { } 
} 

代碼塊類：

public class Block { 

public Block(World world, BodyType type, float width, float height, float x, float y) { 

    PolygonShape pShape = new PolygonShape(); 
    FixtureDef fDef = new FixtureDef(); 
    BodyDef bDef = new BodyDef(); 
    Body body; 

    pShape.setAsBox(width/Game.C, height/Game.C); 
    bDef.position.set(x/Game.C, y/Game.C); 
    bDef.type = type; 
    fDef.shape = pShape; 
    fDef.density = 1.0f; 
    fDef.friction = 0.3f; 
    body = world.createBody(bDef); 
    body.createFixture(fDef); 
    body.setUserData(this); 
    body.setFixedRotation(false); 
    MassData md = new MassData(); 
    md.mass = 5; 
    body.setMassData(md); 
} 
} 

Answer 1

MassData md = new MassData(); 

給出零轉動慣量：md.I == 0所以箱子不旋轉。

如果你

MassData md = body.getMassData(); 

你會根據你的電流密度具有質量和轉動慣量。

改變質量，並得到正確的轉動慣量的最好辦法 - 按照新的質量由自己進行計算，如：

float massScale = [newMass]/md.mass;  
md.mass *= massScale; 
md.I *= massScale; 

這樣，你就可以節省右旋轉點，並有正確的物理慣性。