java - 施加力 - Libgdx

Question

大家好，我试图在 libgdx 中制作这个简单的游戏，一切都很好，直到我注意到我需要施加一个很大的力来让玩家移动一点，有什么方法可以让它需要更少的力吗？这是我渲染播放器的 PlayScreen。`

private Logang game;

//basic playscreen variables
private OrthographicCamera gamecam;
private Viewport gamePort;

//Box2d variables
private World world;
private Box2DDebugRenderer b2dr;

boolean drawn = true;
private Player p;
private int pX = 100, pY = 300;

public GameScreen(Logang game) {

    this.game = game;
    //create cam used to follow mario through cam world
    gamecam = new OrthographicCamera();
    gamecam.update();
    Box2D.init();
    //create our Box2D world, setting no gravity in X, -10 gravity in Y, and allow bodies to sleep
    world = new World(new Vector2(0, Logang.GRAVITY), true);
    //allows for debug lines of our box2d world.
    b2dr = new Box2DDebugRenderer();


    //create a FitViewport to maintain virtual aspect ratio despite screen size
    gamePort = new ScalingViewport(Scaling.fill, Logang.GWIDTH, Logang.GHEIGHT, gamecam);

    p = new Player(new Sprite(new Texture("hud_p3.png")), world, pX, pY, 1);

    //initially set our gamcam to be centered correctly at the start of of map
    gamecam.position.set(gamePort.getWorldWidth() / 2 , gamePort.getWorldHeight() / 2, 0);

    line();
}


@Override
public void show() {

}

public void update(float dt) {
    //handle user input first
    p.update(dt);
    //update our gamecam with correct coordinates after changes
}


@Override
public void render(float delta) {
    //separate our update logic from render
    update(delta);

    //Clear the game screen with Black
    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    world.step(1f / 60f, 6, 2);

    gamecam.position.set(p.getSprite().getX(),Logang.GHEIGHT / 2, 0); // x and y could be changed by Keyboard input for example

    gamecam.update();

    game.getBatch().setProjectionMatrix(gamecam.combined);

    //renderer our Box2DDebugLines
    b2dr.render(world, gamecam.combined);

    System.out.println("Player x: " + p.getSprite().getX() + " Camera X: " + gamecam.position.x + " Body X: " + p.getBody().getPosition().x);
    //System.out.println("Player y: " + p.getSprite().getY() + " Camera Y: " + gamecam.position.y + " Body Y: " + p.getBody().getPosition().y);


    game.getBatch().begin();


    if (p.getBody() != null)
        p.render(game.getBatch());

    EntityManager.renderTerra(game.getBatch(), delta);


    game.getBatch().end();

}

public void line() {
    Texture tmp = new Texture("hud_p3.png");
    tmp.setWrap(Texture.TextureWrap.MirroredRepeat, Texture.TextureWrap.MirroredRepeat);
    for (int i = 0; i < 50; i++) {
        EntityManager.add(new Ground(new Sprite(tmp), world, (int)(i * Logang.TILE), 1, 2));
    }
   // EntityManager.changeSize(((Logang.TILE) * 5),Logang.TILE);
}

@Override
public void resize(int width, int height) {
    //updated our game viewport
    gamePort.update(width, height);
}

public World getWorld() {
    return world;
}

@Override
public void pause() {

}

@Override
public void resume() {

}

@Override
public void hide() {

}

@Override
public void dispose() {
    world.dispose();
    b2dr.dispose();
}`

这是我的实体类，由播放器扩展

 private World world;
private Sprite sprite;
private Body body;
private int tipo;

public Entity(Sprite sprite, World world, int x, int y, int tipo){
    this.sprite = sprite;
    this.world = world;
    getSprite().setPosition(x, y);
    getSprite().setSize(Logang.TILE , Logang.TILE);
    define(tipo);
    this.tipo = tipo;
}

public void update(float dt){
        if(Gdx.input.isKeyPressed(Input.Keys.LEFT)){
            getBody().applyLinearImpulse(new Vector2(-Logang.PPM,0f), getBody().getWorldCenter(), true);
        }
        if(Gdx.input.isKeyPressed(Input.Keys.RIGHT)){
            getBody().applyLinearImpulse(new Vector2(Logang.PPM,0f), getBody().getWorldCenter(), true);
        }
        if(Gdx.input.isKeyPressed(Input.Keys.SPACE)){
            getBody().applyLinearImpulse(0f,-Logang.GRAVITY * Logang.PPM, getBody().getPosition().x, getBody().getPosition().y, true);
        }
    }   
}

public void define(int tipo){
    BodyDef bdef = new BodyDef();
    bdef.position.set((getSprite().getX() + getSprite().getWidth() / 2), (getSprite().getY() + getSprite().getHeight() / 2));
    switch(tipo){
        case 1: {
            bdef.type = BodyDef.BodyType.DynamicBody;
            break;
        }
        case 2:{
            bdef.type = BodyDef.BodyType.StaticBody;
            break;
        }
        case 3:{
            bdef.type = BodyDef.BodyType.DynamicBody;
            break;
        }

    }

    body = world.createBody(bdef);

    FixtureDef fdef = new FixtureDef();
    PolygonShape shape = new PolygonShape();
    shape.setAsBox(getSprite().getWidth() / 2, getSprite().getHeight() / 2);


    fdef.shape = shape;
    body.createFixture(fdef);
    body.setUserData(this);

    shape.dispose();
}

public void render(SpriteBatch batch){
    if(tipo != 2) {
        float posX = getBody().getPosition().x;
        float posY = getBody().getPosition().y;

        getSprite().setPosition(posX - getSprite().getWidth() / 2, posY - getSprite().getHeight() / 2);

    }
    getSprite().draw(batch);
}

public Sprite getSprite() {
    return sprite;
}

public void setSprite(Sprite sprite) {
    this.sprite = sprite;
}

public Body getBody() {
    return body;
}

public void setBody(Body body) {
    this.body = body;
}
}

谢谢大家的回答

Answer 1

Box2D 是一个物理引擎，因此试图在游戏中模仿现实生活中的物理。因此，如果您的物体又大又重，则需要很大的力才能移动它。

为了使您的物体能够以更小的力移动，您可以将它们变小或改变它们的密度以使其更轻，这将允许它们以更小的力移动。

要更改您在 fixtureDefinition 中设置的密度

FixtureDef fdef = new FixtureDef();
fdef.density=0.1f; // (weight: range 0.01 to 1 is good)
fdef.friction = 0.7f; // (how slippery it is: 0=like ice 1 = like rubber)
fdef.restitution = 0.3f; //(how bouncy is it 0= not bouncy 1 = 100% bouncy)

我注意到的另一件事是，您在这条线中使用的力似乎是 PixelPerMeter 比率:

getBody().applyLinearImpulse(new Vector2(-Logang.PPM,0f), getBody().getWorldCenter(), true);

你不应该为你的力使用这个值，因为这是为了将 box2d 世界转换为渲染坐标，你可以使用以下代码将力施加到中心。

getBody().applyLinearImpulse(new Vector2((10f*getBody().getMass()),0f), getBody().getWorldCenter(), true);

作为旁注，脉冲用于创建单一的力应用，而 body.applyForceToCenter(force,wake);用于随时间施加恒定的力。尝试使用 apply force 方法，看看是否有帮助。