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  Rotating rectangles for collisions?  (Read 2526 times)
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Offline cubemaster21
« Posted 2012-08-13 18:03:37 »

Just as the title says, is there any way that I can rotate the rectangle so that i can still call it for collisions? This is what I've got right now, for reference.
I have standard collisions working, but it's a real pain for corners.

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Offline UprightPath
« Reply #1 - Posted 2012-08-13 18:15:38 »

Well, I'm pretty sure that someone else can offer you advice about the actual rotation.

However, if you just need to do the collision check in a sort of quick and dirty way? Well, that's pretty easy since you already know their positions, right?

So, you've got three sets of cases for collisions with rectangles:
1) Rotated rect's corner collides with a stationary: Check if any of the four corners appear inside of another rectangle.
2) Stationary rect's corner collides with rotated: Rotate the corner points of the stationary rect to adjust them be on the Axis Bounded to the rotated one, then check like in 1.
3) Edge collision: Only happens when the rotatable rect is rotated at angel % 90 = 0. Handled like an AABB collision.

Offline The Cure

Senior Newbie





« Reply #2 - Posted 2012-08-14 04:51:42 »

cubemaster21, what are you using to check the standard collisions, shape.intersects()? How are you drawing the rectangle, using the Rectangle2D class?

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Offline cubemaster21
« Reply #3 - Posted 2012-08-14 20:33:55 »

no, This is all with a standard Rectangle() class. And yes, for collisions, i'm using rectangle.intersects.

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Offline The Cure

Senior Newbie





« Reply #4 - Posted 2012-08-15 03:46:33 »

no, This is all with a standard Rectangle() class. And yes, for collisions, i'm using rectangle.intersects.

Try this:

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         int degree = 90; //desired degree
         int rectX = 100, rectY = 100, rectWidth = 150, rectHeight = 100;
         Shape rect = new Rectangle(rectX, rectY, rectWidth, rectHeight); //creating the rectangle you want to rotate
         Rectangle rect2 = new Rectangle(400, 100, rectWidth, rectHeight); //creating other rectangle to check intersection
         AffineTransform transform = new AffineTransform();
         //rotate or do other things with the rectangle (shear, translate, scale and so on)
         transform.rotate(Math.toRadians(degree), rectX + rectWidth /2, rectY + rectHeight /2); //rotating in central axis
         //rect receiving the rectangle after rotate
         rect = transform.createTransformedShape(rect);
         g2d.draw(rect); //Graphics2D object drawing the rectangle on the screen

         //and then check the intersection
        if(rect.intersects(rect2)){
           //Do something...
        }

"A candle loses nothing by lighting another candle" - Erin Majors
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