LibGDX + Box2D : Object Positioning

Question

I'm trying to code some breakout games with LibGDX and Box2D. But there is one point that I don't understand. There are must be two bricks only touch with edge. But on emulator I just saw two bricks nested.

Here's createBox method's code:

private void createBox(float posX, float posY, float boxW, float boxH) {
    BodyDef bodyDef = new BodyDef();
    bodyDef.type = BodyDef.BodyType.StaticBody;
    bodyDef.position.set(posX, posY);

    Body body = world.createBody(bodyDef);

    PolygonShape shape = new PolygonShape();
    shape.setAsBox(boxW, boxH);

    FixtureDef fixtureDef = new FixtureDef();
    fixtureDef.shape = shape;
    fixtureDef.density = 1f;

    Fixture fixture = body.createFixture(fixtureDef);

    shape.dispose();
}

edit: That multiplied code.

createBox(CONS_HOLDER.BRICKS_LEFT_MARGIN + (i * CONS_HOLDER.BRICK_WIDTH * 2 ),
                        CONS_HOLDER.BRICK_TOP_SCREEN_MARGIN + (j * CONS_HOLDER.BRICK_HEIGHT * 2 ) + CONS_HOLDER.BRICKS_TOP_MARGIN,
                        CONS_HOLDER.BRICK_WIDTH / 2,
                        CONS_HOLDER.BRICK_HEIGHT / 2);

Answer 1

The documentation for setAsBox(float, float) states that the parameters are half-width and half-height. You should divide the dimensions of your boxes in half in order to get the correct size.

private void createBox(float posX, float posY, float boxW, float boxH) {
    BodyDef bodyDef = new BodyDef();
    bodyDef.type = BodyDef.BodyType.StaticBody;
    bodyDef.position.set(posX, posY);

    Body body = world.createBody(bodyDef);

    PolygonShape shape = new PolygonShape();
    shape.setAsBox(boxW / 2.f, boxH / 2.f);

    FixtureDef fixtureDef = new FixtureDef();
    fixtureDef.shape = shape;
    fixtureDef.density = 1f;

    Fixture fixture = body.createFixture(fixtureDef);

    shape.dispose();
}

Documentation: https://libgdx.badlogicgames.com/nightlies/docs/api/com/badlogic/gdx/physics/box2d/PolygonShape.html#setAsBox-float-float-