Draw a sprite onto the map not to the screen

Question

I'm using libgdx and I have a tiled map which i want to draw the sprite onto. However the sprite is drawn onto the actual window so when I move the camera, the sprite stays in the same place. ?I want to the sprite to move on the map.

This is how i currently render my objects

    @Override
    public void render(float delta) {
        translateCamera();

        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

        camera.update();

        renderer.setView(camera);

        renderer.render(bgLayers);
        batch.begin();

        batch.draw(splayerSprite, Gdx.graphics.getWidth() / 2,
                Gdx.graphics.getHeight() / 2);

        batch.end();
        renderer.render(fgLayers);

    }

It always end up being in the middle of the screen, however I want to be able to move them seperatly like for example the camera with (W,A,S,D) and move my player with the direction keys. Then if I want the camera locks onto the player but other wise its free.

I'm new to libgdx so please bear with me, Thanks

William Morrison · Accepted Answer

The problem is the SpriteBatch projection matrix isn't being set to the Camera projection matrix. This means the Sprite is not being rendered relative to the Camera. This is why the camera is moving, but the sprite is not; the correct matrix is not being used.

Also the sprite is being rendered always at half the screen's width, and half the screen's height. To fix this Call sprite.draw. This will use the Sprite's internal position.

Set the SpriteBatch projection matrix via batch.setProjectionMatrix(camera.combined). This will cause the sprite to be rendered relative to the camera.

@Override
public void render(float delta) {
    translateCamera();

    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

    camera.update();

    renderer.setView(camera);

    renderer.render(bgLayers);

    //here's the line that was missing.
    batch.setProjectionMatrix(camera.combined);
    batch.begin();

    //be sure to call this instead of specifying position yourself!
    splayerSprite.draw(batch);
    batch.end();
    renderer.render(fgLayers);

}

You'll still need to handle snapping the camera's position to the sprite's position whenever WASD is pressed, but that's trivial.

//snap the camera to the sprite's center.
if(wasd_isDown){
    float centerX = sprite.getX()+sprite.getWidth()/2;
    float centerY = sprite.getY()+sprite.getHeight()/2;
    camera.position.set(x,y, 0);
}

If direction keys are pressed, just translate the camera's position vector via Vector3.add like so:

if(!wasd_isDown){
    float deltaX = 0;
    float deltaY = 0;
    float MOVE_DIST = 10;//or whatever you need.

    if(leftPressed) deltaX = -MOVE_DIST;
    else if(rightPressed) deltaX = MOVE_DIST;

    if(upPressed)deltaY = MOVE_DIST;
    else if(downPressed)deltaY = -MOVE_DIST;

    camera.position.add(deltaX, deltaY, 0);
}

This will allow the camera to move independently only when the player uses directional keys, and will allow the sprite be be rendered in relation to the camera's orientation. It will also snap the camera immediately back to the sprite when WASD is pressed.

Draw a sprite onto the map not to the screen

Answers (2)

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