(LibGDx)Drawing a sprite on to a Box2D body

Newbie & Debugging Questions
#1

I’m still vpretty new to Box2D and I’m following dermetfan’s video using my own code. According to his bitbucket, I’m supposed to render the image on the body like so.

batch.begin();
// renders all the Box2DSprites in the given Box2D World
Box2DSprite.draw(batch, world);
// renders just this Box2DSprite, but you have to give in the Body or Fixture to render on (this way, it doesn't have to be in the user data)
box2DSprite.draw(batch, body);
box2DSprite.draw(batch, fixture);
batch.end();

But using my code , I’m not sure how I would do that. Here is my source if your interested.

Main Gdx Class

public class MyGdxGame extends Game {
	
	@SuppressWarnings("unused")
	private TestScreenA GameScreen;
	
	@Override
	public void create () {
		AssetLoaderTest.loadTile("testImgs/Colors tile.png");
		GameScreen = new TestScreenA(this);

		
	}
	
	@Override
	public void render () {
		GameScreen.render(0);
		
		
	}
}

Test Screen (only screen) Class

public class TestScreenA implements Screen{
	
	@SuppressWarnings("unused")
	private MyGdxGame game;
	Random r;
	
	//Camera 
	private OrthographicCamera camera;
	
	//images etc.
	private SpriteBatch batch;

	Vector3 touch;
	
	
	//Box2D
	private World world;
	private Box2DDebugRenderer b2dr;
	private Body bd;
	
	
	public TestScreenA(MyGdxGame game) {
		
		
		this.game = game;
		//Camera
		camera = new OrthographicCamera();
		//true starts the y axis at the bottom left and false starts it at the top left. It is said that top left is more useul.
		camera.setToOrtho(false, 1000, 1000/16*9);
		batch = new SpriteBatch();
		
		
		
		//Box 2d
		//CREATE WORLD
		world = new World(new Vector2(0, 100f), true);
		b2dr = new Box2DDebugRenderer();
		
		
		
		BodyDef bdef2 = new BodyDef();
		bdef2.position.set(165 , 100 );
		bdef2.type = BodyType.DynamicBody;
		bd = world.createBody(bdef2);
		
		PolygonShape shape2 = new PolygonShape();
		shape2.setAsBox(5, 5 );
		FixtureDef fdef2 = new FixtureDef();
		fdef2.shape = shape2;
		fdef2.restitution = 1f;
		bd.createFixture(fdef2);
		
		
		
		
		// create platform
		BodyDef bdef = new BodyDef();
		bdef.position.set(160 , 120 );
		bdef.type = BodyType.StaticBody;
		Body body = world.createBody(bdef);
		
		PolygonShape shape = new PolygonShape();
		shape.setAsBox(50, 5 );
		FixtureDef fdef = new FixtureDef();
		fdef.shape = shape;
		body.createFixture(fdef);
		
		//********************************************************************************//
		body.setUserData(AssetLoaderTest.blueTile);
		
		//platform 2
		bdef.position.set(160 , 280 );
		bdef.type = BodyType.StaticBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(5 , 5);
		fdef.shape = shape;
		body.createFixture(fdef);
		
		//platform 3
		bdef.position.set(200 , 380 );
		bdef.type = BodyType.StaticBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(100 , 5);
		fdef.shape = shape;
		body.createFixture(fdef);
		
		//platform 4
		bdef.position.set(100 , 500);
		bdef.type = BodyType.StaticBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(80 , 5);
		fdef.shape = shape;
		body.createFixture(fdef);
		
		//platform 4
		bdef.position.set(0 , 0);
		bdef.type = BodyType.StaticBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(2 , 500);
		fdef.shape = shape;
		body.createFixture(fdef);
		
		// create falling box
		bdef.position.set(160 , 200 );
		bdef.type = BodyType.DynamicBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(5 , 5);
		fdef.shape = shape;
		fdef.restitution = 3;
		fdef.density = 40;
		body.createFixture(fdef);
		
		
		//falling box 2
		bdef.position.set(180 , 200 );
		bdef.type = BodyType.DynamicBody;
		body = world.createBody(bdef);
		
		shape.setAsBox(5 , 5);
		fdef.shape = shape;
		fdef.restitution = 5;
		fdef.density = 90;
		
		body.createFixture(fdef);
		
	}
	
	
	public void render(float delta) {
		Gdx.gl.glClearColor(1F, 1F, 1F, 1F);
		Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
		
		camera.update();
		
		batch.setProjectionMatrix(camera.combined);
		
		update(delta);
		
		
		
		batch.begin();
		//batch.draw(AssetLoaderTest.s, 0, 0);
		//batch.draw(AssetLoaderTest.blueTile, 117, 10);
		batch.end();
		
		
		world.step(1.f/60.f, 6, 3);
				
		batch.begin();
		
		//Box2D
		
		//@Param renders world and uses
		b2dr.render(world, camera.combined);
		batch.end();
	}

	public void update(float delta) {
		
		
	}
	
	public void resize(int width, int height) {
		
	}

	public void show() {
		
		
		
	}

	
	public void hide() {
		
	}

	
	public void pause() {
		
	}

	
	public void resume() {
		
	}

	
	public void dispose() {
		
	}

}


Asset Loader Test Class

public class AssetLoaderTest {
	
	//Tile Sheet
	static Texture sSheet;
	static Sprite blueTile;
	
	//Animation
	static Texture sheet;
	static TextureRegion[] sheetFrames;
	static TextureRegion currentFrame;
	static Animation sheetAnim;
	

	
	static void loadTile(String assetPath) {
		
		sSheet = new Texture(assetPath);
		
		blueTile = new Sprite(sSheet, 0, 0, 16, 16);
		
	}
	

}

I hope this isn’t too much code for you to help.

#2

Here is my real world method:


public void alignSpriteWithBody() {
        float facing = MathUtils.radiansToDegrees * (body.getAngle());
        float w = sprite.getWidth();
        float h = sprite.getHeight();
        Vector3 bodyPos = body.getPosition();
        float x = bodyPos.x - w / 2;
        float y = bodyPos.y - h / 2;
	sprite.setOrigin(w / 2, h / 2);
        sprite.setPosition(x, y);
        sprite.setRotation(facing);
    }

looking at it now it could be improved upon, but it does the job well enough

#3

The Image still doesn’t appear. I mainly need to know what I’m doing wrong when i try to render the sprite on the body. I tried messing around with your code and in the gameloop, I set the x, y, width, and height each frame but the sprite just sits there.

#4

I created an int for the x and y and gave both the bdef and the sprite that position. The sprite moves to the location but the body’s gravity moves and the sprite stays static. How do I constantly render the sprite in the body’s location?

#5

I cannot find the lines where you actually draw some Sprites.

Like your alignSpriteWithBody seems fine, however where do you actually call it ?

#6

drawing the sprite is done the most basic way possible so I didn’t include. Nothing to see there.