public static bool TestAABBOBB(Shape s1, Shape s2, ref Contact2D contact)
        {
            CD_AABB2D a = (CD_AABB2D)s1;
            CD_OBB2D b = (CD_OBB2D)s2;

            // Transform AABB into OBB space
            Vector2 min = Vector2.Transform(a.MinPoint, b.World_Transform);     // MinPoint is in World Coordinates
            Vector2 max = Vector2.Transform(a.MaxPoint, b.World_Transform);     // MaxPoint is in World Coordinates
            Vector2 dim = max - min;

            //(max + min) * 0.5f
            CD_AABB2D c = new CD_AABB2D(b.Position, dim.X, dim.Y); 

            return TestAABBAABB(a, c, ref contact);
        }

                    world_Transform =
                        // Translate centroid to origin first (only required if centroid is not (0,0,0))
                        //Matrix.CreateTranslation(new Vector3(-centre, 0.0f)) * 
                        Matrix.CreateScale(width, height, 0f) *
                        Matrix.CreateRotationZ(rotation) *
                        Matrix.CreateTranslation(position.X, position.Y, 0f);

        public static bool TestAABBAABB(Shape s1, Shape s2, ref Contact2D contact)        {            CD_AABB2D a = (CD_AABB2D)s1;            CD_AABB2D b = (CD_AABB2D)s2;            // [Separating Axis Theorem]            // • Two convex shapes only overlap if they overlap on all axes of separation            // • In order to create accurate responses we need to find the collision vector (Minimum Translation Vector)               // • Find if the two boxes intersect along a single axis             // • Compute the intersection interval for that axis            // • Keep the smallest intersection/penetration value            // Minimum Translation Vector parameters            float mtv_Distance = float.MaxValue;            // Set current minimum distance (max float value so next value is always less)            int mtv_Axis = 0;                               // Axis along which to travel with the minimum distance            // For each separating axis            for (int i = 0; i < 2; ++i)            {                // Find distance intervals for current two slabs                // Distance is between slab min/max values                float d_S0 = a.MinPoint.Index(i) - b.MaxPoint.Index(i);                float d_S1 = b.MinPoint.Index(i) - a.MaxPoint.Index(i);                // The distance is positive if the intervals do not overlap                // Must be >= to 0 and not > 0, otherwise MTV can equal Vector2.Zero and cause NaN                if (d_S0 >= 0f || d_S1 >= 0f)                {                    return false;                }                // Current distance interval for slabs                float d = (d_S0 > d_S1) ? -d_S0 : d_S1;                // If d is the smallest distance so far                if (Math.Abs(d) < Math.Abs(mtv_Distance))                {                    // Store the distance and the current axis                    mtv_Distance = d;                    mtv_Axis = i;                }            }            // Minimum Translation Vector            Vector2 mtv = Vector2.Zero;            switch (mtv_Axis)            {                case 0:                    mtv.X = mtv_Distance;                    break;                case 1:                    mtv.Y = mtv_Distance;                    break;            }            contact.normal = Vector2.Normalize(mtv);            contact.penetration = Math.Abs(mtv_Distance) + Settings.EPSILON;            // Get the AABB support points using the MTV            Vector2[] supportA = a.FindSupportPoints(contact.normal);            Vector2[] supportB = b.FindSupportPoints(-contact.normal);            //contact.point = GetContactPoints(supportA, supportB);            return true;        }

        public static CD_AABB2D ComputeFromOBB(CD_OBB2D obb)        {            Vector2 position = new Vector2();            position.X += Vector2.Dot(obb.Position, Vector2.UnitX);            position.Y += Vector2.Dot(obb.Position, Vector2.UnitY);            // Compute the projection interval radius of obb onto world unit x axis            float r_X = obb.Extents.X * Math.Abs(Vector2.Dot(Vector2.UnitX, obb.Axis_X)) +                obb.Extents.Y * Math.Abs(Vector2.Dot(Vector2.UnitX, obb.Axis_Y));            // Compute the projection interval radius of obb onto world unit y axis            float r_Y = obb.Extents.X * Math.Abs(Vector2.Dot(Vector2.UnitY, obb.Axis_X)) +                obb.Extents.Y * Math.Abs(Vector2.Dot(Vector2.UnitY, obb.Axis_Y));            Vector2 extents = new Vector2();            extents.X = r_X;            extents.Y = r_Y;            return new CD_AABB2D(position, extents.X * 2, extents.Y * 2);        }

        private static bool TestRadiusRadius(Shape s1, Shape s2)        {            // Calculate squared distance between centres            Vector2 v = s1.Position - s2.Position;            float distance_Squared = Vector2.Dot(v, v);            float radius_Sum = s1.Radius + s2.Radius;            float radius_Sum_Squared = radius_Sum * radius_Sum;            // Spheres intersect if squared distance is less than squared sum of radii            if (distance_Squared < radius_Sum_Squared)            {                return true;            }            return false;        }