I think I am getting clockwise, because the points are input in X-Y format (and not in row-column format). So, the X axis grows horizontally towards right, and Y axis vertically downwards. Hence, we can think of the image plane as a mirror image of X>0, Y>0 plane about the X axis. => the standard y/x that normally gives angle anticlockwise, will now give the angle in clockwise direction.

I also tried it out with a sample program:
```c++
int main() {
    Mat image(300, 300, CV_8UC3, Scalar(0));
    RotatedRect r(Point2f(0,0), Point2f(100,100), Point2f(50, 150));
    Point2f vertices[4];
    r.points(vertices);
    
    for (int i = 0; i < 4; i++)
            line(image, vertices[i], vertices[(i+1)%4], Scalar(0,255,0));
    imwrite("rect.jpg", image);
}
```

The output of which was:
![rect](https://f.cloud.github.com/assets/1893429/2208115/096ea61e-997c-11e3-9f0b-8314cd94eb8e.jpg)

Please do let me know if I'm mistaken somewhere. Thanks!