Bdtjtk

I have been working with box2d and am having a problem where my body is not being set to the correct y coordinate when I try to position it at the bottom right of the screen.

I am trying to set the y coordinate to 0 so that the body aligns directly with the bottom of the screen. However, the half of the body is hanging off the screen. Even when I print out the body's location, it says the y is at 0.

I have my pixel per meter set at screenHeight / 80 which comes out to be around 25 PPM for the current devise I am using. I am not sure if my scaling is causing something weird to happen.

Code:

public class GameScreen extends ScreenAdapter {

    Controller game;



    public World world;

    public Body ball;

    public Body block;

    public Box2DDebugRenderer box2DDebugRenderer;

    private Matrix4 cameraBox2D;



    public MyGestureListener myGestureListener;



    //x-axis length for top/bottom bar

    private float goalWidth;



    //pixels per meter

    public float PPM;



    //y-axis height for back bar

    private float goalHeight;

    private float goalPostThickness;



    //Screen height and width

    private float screenWidth;

    private float screenHeight;



    //How far down/up posts are from edge of screen

    private float goalPostTopOffset;

    private float goalPostBottomOffset;



    //Center x,y of cannon

    private float cannonOriginX; //Variables used for starting poisition of balls

    private float cannonOriginY;



    //Center x,y of ball

    float ballX;

    float ballY;



    //Velocity of ball

    public float velocity = 50;

    public int colorCode = 1;



    //Tracks users drag y coord

    public float panLocation = 0;



    //Velocity of block once the user releases

    public float flingVelocity;



    //Changes to true when the block is released

    public boolean isReleased = false;



    public GameScreen (Controller game){

        this.game = game;

    }



    @Override

    public void show(){



        myGestureListener = new MyGestureListener(game, this);

        cameraBox2D = new Matrix4(game.cam.combined);



        screenWidth = game.getScreenWidth();

        screenHeight = game.getScreenHeight();



        //PPM = screenHeight / 80f;



        PPM = screenHeight / 80f;



        goalPostTopOffset = screenHeight/7;

        goalPostBottomOffset = goalPostTopOffset * 3;

        goalHeight = screenHeight - (goalPostTopOffset + goalPostBottomOffset);

        goalWidth = screenWidth / 6;

        goalPostThickness = screenWidth / 75;



        cannonOriginX = goalWidth / 2; //Variables used for starting position of balls

        cannonOriginY = (goalPostThickness*5) / 2;



        ballX = 0 + cannonOriginX;

        ballY = (goalPostBottomOffset - (goalPostBottomOffset / 4)) + cannonOriginY;



        world = new World(new Vector2(0, 0f), true);

        box2DDebugRenderer = new Box2DDebugRenderer();



        //Creates animated ball

        ball = createBall();



        //Sets radius, density, etc.

        setBallProperties(ball);



        //Creates block that stops balls

        block = createBlock();



        //Sets properties

        setBlockProperties(block);

    }



    @Override

    public void render(float delta){

        //Logic

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



        //Draw

        game.cam.update();

        Gdx.gl.glClearColor(32/255f, 32/255f, 32/255f, 0);

        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);



        box2DDebugRenderer.render(world, game.cam.combined.scl(PPM));

        game.shape.setProjectionMatrix(game.cam.combined);



        Gdx.input.setInputProcessor(new GestureDetector(myGestureListener));



        System.out.println(block.getPosition().y);

        System.out.println(block.getPosition().x);



        drawNonAnimated();

        drawAnimated();





//show()

        cameraBox2D = game.cam.combined.cpy(); //Copy the main camera

        cameraBox2D.scl(PPM); //Scale the camera projection to the ratio you're using for Box2D



//render()

        box2DDebugRenderer.render(world, cameraBox2D);

    }



    @Override

    public void hide(){



    }



    //draws stationary objects such as goal posts

    public void drawNonAnimated(){



        //Cannon platform

        game.shape.setColor(1, 1, 1, 1);

        game.shape.begin(ShapeRenderer.ShapeType.Filled);

        game.shape.rect(0, (goalPostBottomOffset - (goalPostBottomOffset / 4))/PPM, goalWidth/PPM, (goalPostThickness*2)/PPM);

        game.shape.end();



        //Cannon

        game.shape.setColor(1, 1, 1, 1);

        game.shape.begin(ShapeRenderer.ShapeType.Filled);

        game.shape.rect(0, (goalPostBottomOffset - (goalPostBottomOffset / 4))/PPM, cannonOriginX/PPM,

                cannonOriginY/PPM, goalWidth/PPM, (goalPostThickness*5)/PPM, 1, 1, 45);

        game.shape.end();

    }



    public void drawAnimated(){

        //FOR BALL

        velocity--;

        ball.setLinearVelocity(new Vector2(35,velocity));



        Vector2 pos = ball.getPosition();



        if (pos.x >= screenWidth/PPM){

            ball.setTransform(new Vector2(ballX/PPM, ballY/PPM), 0);



            //Changing color of ball each loop

            if (colorCode == 3){

                colorCode = 1;

            }

            else{

                colorCode++;

            }

            //max 75   min 50

            velocity = randInt(50, 75);

        }



        attachCircleShape(pos);



        blockerMovement();



    }



    public void blockerMovement(){

        //FOR BLOCKER RECTANGLE ANIMATION

        Vector2 pos = block.getPosition();

        float boundaryLocation = (goalPostBottomOffset - (goalPostBottomOffset / 4))/PPM;

        //attachBlockerShape(pos);



        panLocation = myGestureListener.getPanLocation();

        if (isReleased == true){

            //Get the velocity as the block is released

            //to determine the speed it will continue to go after release

            block.setLinearVelocity(0, flingVelocity);

            flingVelocity -= 3;

        }



        else if (myGestureListener.getCheckRelease()|| panLocation/PPM >= boundaryLocation && !isReleased) {

            flingVelocity = myGestureListener.speed;

            isReleased = true;

            System.out.println("SPEED: " + flingVelocity);

        }

        else if (myGestureListener.isPaning) {



            block.setTransform(new Vector2((screenWidth - goalPostThickness) / PPM, panLocation / PPM), 0);

        }



    }



    //Creates animated ball

    public Body createBall(){

        Body bBody;

        BodyDef def = new BodyDef();

        def.type = BodyDef.BodyType.DynamicBody;

        def.position.set(ballX/PPM,ballY/PPM);

        def.fixedRotation = true;

        bBody = world.createBody(def);



        return bBody;

    }



    //Sets radius, density, etc.

    public void setBallProperties(Body body){

        float gbt = screenWidth / 75;  //Goal post thickness

        float ballRadius = (gbt * 1.5f) / PPM;



        // Create a circle shape and set its radius to 6

        CircleShape circle = new CircleShape();



        circle.setRadius(ballRadius);

        // Create a fixture definition to apply our shape to

        FixtureDef fixtureDef = new FixtureDef();

        fixtureDef.shape = circle;

        fixtureDef.density = 3.5f;

        fixtureDef.friction = 0.4f;

        fixtureDef.restitution = 0.6f; // Make it bounce a little bit



        // Create our fixture and attach it to the body

        Fixture fixture = ball.createFixture(fixtureDef);



        circle.dispose();

    }







    public Body createBlock(){

        Body bBody;

        BodyDef def = new BodyDef();

        def.type = BodyDef.BodyType.DynamicBody;

        def.position.set((screenWidth - goalPostThickness)/PPM,0);

        def.fixedRotation = true;

        bBody = world.createBody(def);



        return bBody;

    }





     //Sets radius, density, etc.

    public void setBlockProperties(Body body){

        float gbt = screenWidth / 75;  //Goal post thickness



        // Create a circle shape and set its radius to 6

          PolygonShape square = new PolygonShape();

         square.setAsBox(goalPostThickness/PPM, (goalWidth/2)/PPM);



        // Create a fixture definition to apply our shape to

        FixtureDef fixtureDef = new FixtureDef();

        fixtureDef.shape = square;

        fixtureDef.density = 3.5f;

        fixtureDef.friction = 0.4f;

        fixtureDef.restitution = 0.6f; // Make it bounce a little bit



        // Create our fixture and attach it to the body

        Fixture fixture = block.createFixture(fixtureDef);



        square.dispose();

    }



    public static int randInt(int min, int max) {

        Random rand = new Random();

        int randomNum = rand.nextInt((max - min) + 1) + min;

        return randomNum;

    }



    public void attachBlockerShape(Vector2 pos){

        game.shape.setColor(1, 1, 1, 1);

        game.shape.begin(ShapeRenderer.ShapeType.Filled);

        game.shape.rect(pos.x, pos.y, goalPostThickness/PPM, (goalWidth/2)/PPM);

        game.shape.end();

    }



    //Attaching a regular libgdx shape to the position of box2d shape

    public void attachCircleShape(Vector2 pos){

        //Color of ball changes each loop

        if (colorCode == 1){

            //Blue

            game.circle.setColor(66/255f, 134/255f, 244/255f, 0);

        }

        else if (colorCode == 2){

            //Pink

            game.circle.setColor(244/255f, 66/255f, 116/255f, 0);

        }

        else if (colorCode == 3){



            game.circle.setColor(244/255f, 116/255f, 66/255f, 0);

        }

        game.circle.begin(ShapeRenderer.ShapeType.Filled);

        game.circle.circle(pos.x*PPM, pos.y*PPM, goalPostThickness * 1.5f);

        game.circle.end();

        game.cam.update();



    }

    @Override public void dispose(){

        box2DDebugRenderer.dispose();

        world.dispose();

    }





}

If you create a Body with Box2d 0,0 is in the center of the Body while libgdx set 0,0 on the bottom left corner.

So if you create a Body with Box2d and you want that 0,0 is in the bottom left corner you must move the Body by half of width on x and half of height on y:

public Body createBody(float x, float y, float width, float height){

    BodyDef bodyDef = new BodyDef();

    bodyDef.type = BodyDef.BodyType.DynamicBody;



    //Move the body so if x and y are 0 the bottom left corner of the body is on position 0,0

    bodyDef.position.x = x + width / 2;

    bodyDef.position.y = y + height / 2;



    PolygonShape polygonShape = new PolygonShape();

    polygonShape.setAsBox(width / 2, height / 2);



    FixtureDef fixtureDef = new FixtureDef();

    fixtureDef.shape = polygonShape;



    Body body = world.createBody(bodyDef);

    body.createFixture(fixtureDef);



    polygonShape.dispose();

    return body;

}