Collision detection with rotating shapes

[Kalle Zander]

Shape sprite;
double rotationAngle, positionX, positionY;
///...
public void draw(Graphics2D g2)
{
	g2.draw(sprite.getBounds());	
	g2.rotate(rotationAngle, positionX, positionY);
	g2.fill(sprite);
}

I'm trying to perform collision detection with shapes that rotates on the screen using the Graphics2D rotation. The problem is that I need to rotate the sprite.getBounds() Rectangle in some way after the graphics rotation so it fits well so I later on can use the intersect method with decent accuracy. As the above code is now, the sprite.getBounds() Rectangle follows the sprite in x and y, but doesn't rotate with it as can be seen in the images below. Is there some method to rotate the actual sprite.getBounds() Rectangle's coordinates, or how can this problem be approached in best way?



//Kalle

[Jelle Klap]

You could pair the sprite with a java.awt.geom.Area, rotate the sprite using an AffineTransform and pass that AffineTransform instance to the Area.transform() method. You can then use Area.getBounds() / getBounds2D() to obtain the post-rotation coördinates for your sprite.

[Campbell Ritchie]

If you use AffineTransforms, apply them to a cloned copy of the Graphics object, obtained with a method of the Graphics class, I think called create().

[Kalle Zander]

Jelle Klap wrote:You could pair the sprite with a java.awt.geom.Area, rotate the sprite using an AffineTransform and pass that AffineTransform instance to the Area.transform() method. You can then use Area.getBounds() / getBounds2D() to obtain the post-rotation coördinates for your sprite.

public void draw(Graphics2D g2)
{		
	AffineTransform at = new AffineTransform();
	at.rotate(rotation,x,y);

	Area a = new Area(myShape);
	a.transform(at);
	g2.draw(a.getBounds2D());
		
    g2.setTransform(transformer);
	g2.fill(at.myShape);	
}

If this was what you meant, it worked fine! Thank you.