Why some games have problems with animations at 60 fps?

I bought Resident Evil 4 on Steam recently and I noticed that while 60 fps works great and makes it much better than the old 30 fps, some stuff like the fire, explosions and the rifle reloading animation still run at 30 fps. And after reading some patch notes, apparently some other stuff was weird at launch too (like the chicken laying eggs twice as fast) although they have been fixed.

This got me looking into games that have problems running at 60 fps and apparently there are a few, including Halo 1 on Xbox One, which has some of the background animations still locked at 30 fps despite the game being in 60 fps (according to Digital Foundry) even though they are minor problems.

So that got me wondering why is that? Obviously most games have no such issues, but why would some have problems? I understand it has to do with the way animations were keyframed and while I understand what keyframing means, I dont understand why it only affects certain games.

As I understand it, it was animated at 30 frames, and was simply never properly implemented to support doubling the framerate.

I came across something similar with crysis 3 in the second level outdoors the grass movement

seems really off visually its very jarring and not nice to look at. have no idea what rendering speed was used. but something about the first two levels of that game seem to run like poop. so might have something to do with that, i dunno.

Did you play it at medium settings, or had some enviroment setting at medium? I remember reading that some stuff renders at half the framerate at lower settings. I played that game at 30 fps to get the better graphics so I didnt notice it.

My input as an apprenti coder:

Games work in step. One step renders a frame. A 30-fps game should go through 30 steps a second, whereas a 60-fps game should go through 60. Every step the all the coding of all the object goes through. If there's too much coding to go through and the processor can keep up, you'll lose framerate.

It becomes problematic with the timer. You cannot code "wait 1 second". You have to code "wait 30 steps". In a small game, going from 30 to 60 would be a matter of just changing 30 steps to 60 everywhere, but I'm sure more complex games have quite a few systems than would need new code for them to work properly at 60. Thus it become easier to keep an object working like it would be in a 30 fps game. Also, if your calculation works on a 30 fps system, just having it change to 60 fps might creates issue, like the game not having enough time to recognize collisions, essentially making objects clip through each other.

I'm just guessing. I mostly have no idea what I'm saying and somebody with better programming skill than I (and better english) could probably explain better.

@zamolxes: Well you already spelled out the answear. Games not made and optimized for 60FPS will probably be glitchy when you just upp the FPS count. Also Halo 1 and 2 in the MCC running at 60FPS is a joke and i dont know where that rumor started but its sluggish like hell all the time, if you compare it to Halo 3 its night and day. Especially with the remastered graphics it runs really bad and it seems amazing how they managed that.

If you play Dark Souls with DSfix at 60 FPS your jump distance becomes much shorter, which makes most jumps impossible to do. It has something to do with the point at which the game calculates gravity, as normally your character has a bit of float to their jump but at 60 FPS the float time is, well, halved.

As far as I know it's often not the animation that is the problem at all, but the way the game runs its calculations based on the desired framerate.