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Circular and polygonal collision with Libgdx

Is there a way in Libgdx to check for a collision between a polygon and a circle?

I saw the Intersector class, but found only a collision for Circle and Rectangle. What about any other Polygon?

If I need to do this manually, what's the best way to do this with Libgdx?

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java polygon collision-detection circle libgdx
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3 answers

So, I managed to create a method for checking collisions between a circle and a polygon. At least it works for me.

Here is the code:

 public boolean overlaps(Polygon polygon, Circle circle) { float []vertices=polygon.getTransformedVertices(); Vector2 center=new Vector2(circle.x, circle.y); float squareRadius=circle.radius*circle.radius; for (int i=0;i<vertices.length;i+=2){ if (i==0){ if (Intersector.intersectSegmentCircle(new Vector2(vertices[vertices.length-2], vertices[vertices.length-1]), new Vector2(vertices[i], vertices[i+1]), center, squareRadius)) return true; } else { if (Intersector.intersectSegmentCircle(new Vector2(vertices[i-2], vertices[i-1]), new Vector2(vertices[i], vertices[i+1]), center, squareRadius)) return true; } } return false; }
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Unfortunately, I do not have enough reputation for comments, so I am adding this as another answer instead ...

Cristiano is great for checking that a circle overlaps one of the segments of a polygon line, but he does not verify that the more unusual case is when the circle is completely inside the polygon, which can happen if a small fast moving circle collides with a large polygon.

I tried the code below for Cristiano with a little modification to fix the problem ...

 public static boolean overlaps(Polygon polygon, Circle circle) { float []vertices=polygon.getTransformedVertices(); Vector2 center=new Vector2(circle.x, circle.y); float squareRadius=circle.radius*circle.radius; for (int i=0;i<vertices.length;i+=2){ if (i==0){ if (Intersector.intersectSegmentCircle(new Vector2(vertices[vertices.length - 2], vertices[vertices.length - 1]), new Vector2(vertices[i], vertices[i + 1]), center, squareRadius)) return true; } else { if (Intersector.intersectSegmentCircle(new Vector2(vertices[i-2], vertices[i-1]), new Vector2(vertices[i], vertices[i+1]), center, squareRadius)) return true; } } return polygon.contains(circle.x, circle.y); }
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... and follow Phil Anderson's wonderful answer, here is my version that just avoids creating new Vector2s every check and instead reuses static instances of Vector2.

 public class PolygonUtil { static final Vector2 center = new Vector2(); static final Vector2 vec1 = new Vector2(); static final Vector2 vec2 = new Vector2(); public static boolean overlaps(Polygon polygon, Circle circle) { float []vertices=polygon.getTransformedVertices(); center.set(circle.x, circle.y); float squareRadius=circle.radius*circle.radius; for (int i=0;i<vertices.length;i+=2){ if (i==0){ if (Intersector.intersectSegmentCircle(vec1.set(vertices[vertices.length - 2], vertices[vertices.length - 1]), vec2.set(vertices[i], vertices[i + 1]), center, squareRadius)) return true; } else { if (Intersector.intersectSegmentCircle(vec1.set(vertices[i-2], vertices[i-1]), vec2.set(vertices[i], vertices[i+1]), center, squareRadius)) return true; } } return polygon.contains(circle.x, circle.y); }

}

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