occasionally i remember that inverse kinematics is computationally easy and it's just. how
@Felthry rendering mirrors, I suppose!
@Felthry The hard part with IK is not doing it per se, but working out how to do it. That was a big deal fifteen years ago, but it's basically done now. The solutions are now fairly well known and just need to be implemented.
As for stuff that's harder than expected? Well, an old one comes to mind. Consider the halting problem, or whether a given computer program will go into an infinite loop or not. Sounds straightforward enough, but it's actually a mathematical impossibility to determine this programmatically.
inverse kinematics is possibly the best example of something being way easier than expected, but what's the best example of something being way harder than expected?