Been struggling with problems with rotating quads all night. Finally got it sorted and can now sleep.
A big thanks to Todo for all his efforts and useful advice. Wish you could rate people up more than once.
Proof that my rotation thing works
Morning. God I'm tired. It was a long and frustrating five hours last night getting the rotation to work, especially since my girlfriend nicked the computer halfway through to mess about on FriendsReunited, but it was a great feeling when I got it sorted.
My library now has the capacity to rotate any quad about its centre before drawing it, which is all the functionality I want for now. I might extend this later, but I'm happy enough.
So now I can draw even less sprites since I can use rotation animations on static frames and stuff will still look cool. Yay!
Udo will probably now get a spin attack of some kind and I predict levels with lots of large machinery (spinning gears, spinning fans). Pendulum-style blades on ropes are now quite feasible and I suspect that the enemies may even spin around when you kill them.
Motto for the next few days - "If it don't spin, it ain't in."