libGDX collision detection / bounding the object

Question

I am trying to implement collision detection so I am drawing a red rectangle to see if it is working. When I put the code below into the update method to check if it is going to work the position is not in the right place. The red rectangle starts from the middle and not at the x and y point? So it draws it wrong.

I also have a getter method so nothing wrong there.

bullet.set(getX(), getY(), getOriginX(), getOriginY());

this is for the render

shapeRenderer.begin(ShapeType.Filled);
shapeRenderer.setColor(Color.RED);
shapeRenderer.rect(bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), 15, 5, bullet.getRotation());
shapeRenderer.end();

I have tried to do it with a circle but the circle draws in the middle and I want it to be at the tip of the bullet. At the front of the bullet. x, y point.

boundingCircle.set(getX() + getOriginX(), getY() + getOriginY(), 4.0f);

shapeRenderer.begin(ShapeType.Filled);
shapeRenderer.setColor(Color.RED);
shapeRenderer.circle(bullet.getBoundingCircle().x, bullet.getBoundingCircle().y, bullet.getBoundingCircle().radius);
shapeRenderer.end();

I need it to be of the x and y as the bullet is in the middle of the sprite when drawn originally via paint.

Answer 1

To change the origin of your bounds, you can add the width/height of the rectangle, or subtract.

If the origin of the rectangle is bottom left but you need it positioned from the centre, you would do:

rect.x + (width / 2), rect.y + (height / 2)

This will take the x coordinate, add the half width on which puts the x value at a midpoint along the rect.

Play around with this to fit your code.