Box2DX.Collision.CircleShape.ComputeSubmergedArea C# (CSharp) Метод

        public override float ComputeSubmergedArea(Vec2 normal, float offset, XForm xf, out Vec2 c)
        {
            Vec2 p = Box2DX.Common.Math.Mul(xf, _localPosition);
            float l = -(Vec2.Dot(normal, p) - offset);
            if (l < -_radius + Box2DX.Common.Settings.FLT_EPSILON)
            {
                //Completely dry
                c = new Vec2();
                return 0;
            }
            if (l > _radius)
            {
                //Completely wet
                c = p;
                return Box2DX.Common.Settings.Pi * _radius * _radius;
            }

            //Magic
            float r2 = _radius * _radius;
            float l2 = l * l;
            float area = r2 * ((float)System.Math.Asin(l / _radius) + Box2DX.Common.Settings.Pi / 2) +
                l * Box2DX.Common.Math.Sqrt(r2 - l2);
            float com = -2.0f / 3.0f * (float)System.Math.Pow(r2 - l2, 1.5f) / area;

            c.X = p.X + normal.X * com;
            c.Y = p.Y + normal.Y * com;

            return area;
        }