在libgdx中渲染box2d

Question

我有一个使用FitViewport的尺寸为800x480的游戏世界，最初使用像素来渲染box2d物体+固定装置，因此所有物理效果看起来都是漂浮而缓慢的。通过查看文档，我发现box2d使用度量单位，因此我将box2d的位置和大小转换为32倍，因此最终得到了25x15米的box2d世界。

我遇到的问题是，现在box2d对象变得非常小。如何缩小它们，使它们在屏幕上显示常规尺寸？

Answer 1

您需要在world和box2之间使用转换因子。

在您的create（）中，您将拥有：

private OrthographicCamera camera;
private BodyDef bodyDef;
private Body body;
private PolygonShape box;
static float WORLD_TO_BOX, BOX_TO_WORLD, bodyWidth, bodyHieght;

public Create(){
    //Conversion factors
    WORLD_TO_BOX = 1/32f;  
    BOX_TO_WORLD = 1/WORLD_TO_BOX;

    //Creation of the camera with your factor 32
    camera = new OrthographicCamera();
    camera.viewportHeight = Gdx.graphics.getHeight() * WORLD_TO_BOX;  
    camera.viewportWidth = Gdx.graphics.getWidth() * WORLD_TO_BOX;  
    camera.position.set(camera.viewportWidth/2, camera.viewportHeight/2, 0f);  
    camera.update();

    //Let's say you want to create a body in the center of your screen
    BodyDef = new BodyDef();  
    BodyDef.position.set(new Vector2(camera.viewportWidth/2, -camera.viewportHeight/2));  
    body = world.createBody(BodyDef);  
    box = new PolygonShape();  
    //Let's say you want your body to have the shape of a square which sides size is one fifth of your camera width
    bodyWidth = camera.viewportWidth/10;
    bodyHeight = camera.viewportWidth/10;
    box.setAsBox(bodyWidth, bodyHeight);
    body.createFixture(box, 0.0f);
}

目前，您仅使用转换因子WORLD_TO_BOX来创建相机。但是，如果要在身上绘制一些精灵，可以在render（）中使用BOX_TO_WORLD因子。例如，您要使用spritebatch在您的正方形上以正确的大小和位置在正方形的render（）中绘制一个sprite：

private Texture texture;

public void render(){
    game.batch.begin();
    game.batch.setColor(1,1,1,1);
//In Box2D, the orgin of a body is the center of the body, 
//while in your world the orgin of a sprite is the bottom left corner
//I Box2D the width and the height of a body will be twice the values you entered,
//while in your world the width and the height of a sprite are the exact values you entered.
//Taking all this into account, to draw a sprite above a body you need to :
//1 - center the sprite above the body. Ex : (body.getPosition().x - bodyWidth) for the X position
//2 - draw the sprite at the right size, taking in account the factor 2. Ex : bodyWidth * 2 for the widht of the sprite
//3 - Apply the BOX_TO_WORLD factor to all every sizes and distances
    game.batch.draw(texture,
                    BOX_TO_WORLD * (body.getPosition().x - bodyWidth),
                    BOX_TO_WORLD * (body.getPosition().y - bodyHeight),
                    BOX_TO_WORLD * bodyWidth * 2,
                    BOX_TO_WORLD * bodyHeight * 2);
     game.batch.end();
}

希望它能回答您的问题。