How can I rotate Rectangles in Libgdx?

Question

I rotated my sprite 90 degrees and I want to do the same with my rectangle to be able to use them for collision, but the rotate() method is not available on rectang

Answer 1

The other answer is basically correct; however, I had some issues with the positioning of the polygons using that method. Just some clarification:

LibGDX does not support rotated Rectangles when using the Intersector for collision dectection. If you need rotated rectangles, you should use the Polygon for collision detection instead.

Building a Rectangular Polygon:

polygon = new Polygon(new float[]{0,0,bounds.width,0,bounds.width,bounds.height,0,bounds.height});

Don't forget to set the origin of the Polygon if you are going to rotate it:

polygon.setOrigin(bounds.width/2, bounds.height/2);

Now you can rotate the collision polygon:

polygon.setRotation(degrees);

Also, somewhere in your code, you will likely want to update the position of the collision polygon to match your sprite:

polygon.setPosition(x, y);

We can even draw our polygon on screen (for debug purposes):

drawDebug(ShapeRenderer shapeRenderer) {
    shapeRenderer.begin(ShapeRenderer.ShapeType.Line);
    shapeRenderer.polygon(polygon.getTransformedVertices());
    shapeRenderer.end();
}

Collision Detection:

The overlapConvexPolygons() of the Intersector:

boolean collision = Intersector.overlapConvexPolygons(polygon1, polygon2)

As mentioned in the other answer, this method only works if:

• using convex polygons, which the rectangle is
• performing polygon to polygon checks, e.g.: you cannot mix rectangles and polygons

Answer 2

Rotation

You could create a Polygon from the rectangle or from the sprite (supplying the vertices in order for the polygon constructor) and use it's rotate(float degrees) method:

treePoly = new Polygon(new float[] {
               treeRect.x, treeRect.y,
               treeRect.x, treeRect.y + treeRect.height,
               treeRect.x + treeRect.width, treeRect.y + treeRect.height,
               treeRect.x + treeRect.width, treeRect.y
           });

treePoly.rotate(45f);

Collision Detection

Collision checks then could be done via the Intersector class:

Intersector.overlapConvexPolygons(polygon1, polygon2)

Keep in mind though, this method only works if:

• you use convex polygons, which the rectangle is
• you do polygon to polygon checks, e.g.: you cannot mix rectangles and polygons

Answer 3

I think something like it can help, I can not test now,

//Rectangle
 treeRect=new Rectangle(treeSpr.getX(),
                        treeSpr.getY(),
                        treeSpr.getHeight(), //now is change width by height
                        treeSpr.getWidth());  //now is change height by width

Note: may You need to adjust the origin of the rotation for both

you can use a render ShapeRenderer to see if the result is as expected:

add for test in variable class

private ShapeRenderer sRDebugRectangel = new ShapeRenderer();

add for test in update or draw

sRDebugRectangel.begin(ShapeType.Filled);
sRDebugRectangel.identity();

sRDebugRectangel.rect(yourRectangle.getX(), 
                      yourRectangle.getY(),
                      yourRectangle.getWidth(),
                      yourRectangle.getHeight());

sRDebugRectangel.end();

can look at my answer to this question to use a shaperrender otherwise known as:

Libgdx, how can I create a rectangle from coordinates?