   Rotated sprite collision detection
  I am using directx to program a 2d sprite engine. I have a class which represents an image on the screen called jSprite. This class contains the d3d texture and float values of all the possible transformations. My collision detection function accepts 2 jSprite objects and should return true if any overlap exists between the sprites. So far, I have been using simple bounding rectangles, which work alright with non-rotated sprites. The problem with my current algorithm is that it does not account for the rotation, center of rotation, or scaling factors.I found this article: http://www.gamedev.net/reference/articles/article2604.asp ,which would probably work for what I need, but it does not explain how to find the verticies of the rotated rectangles. I was thinking I could find the new points given a transformation matrix and the initial points, but I do not know how to do this. Another thing I was thinking of doing is using bounding circles for all my images, but I would still need a way to account for the rotation around a point other than the center of the sprite. Any help with this would be greatly appreciated.   
  google rotation matrices and you'll see how to rotate a point in space.  The rotation happens about the centre (0,0).  If you want to rotate about a different point in space then you first move your point so that the centre of rotation is at 0,0 then rotate and then move everything back to where it was.   