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[Archived] Skin animation modification allows for alteration of AR

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Topic Starter
Mafham
TL;DR first, the hitcircleoverlay.png texture is animatable for up to 4 frames, each frame lasting 500ms, and it is possible to use this in conjunction with low gamma to make reading low AR much easier (turns AR5 into about AR8.2). Anecdotally I have only seen this used for its intended purpose of aesthetic in 1 skin, out of the over 100 skins that I have played with. Most other animatable elements in osu! can use thousands of frames, but this is limited to just 4, presumably to prevent its use for AR manipulation. Can this animation be removed, since it is causing much more harm than good?

This trick has been known for quite some time, to my knowledge it was first discovered around the time of this Reddit post in 2015. In this example, the skin uses blank textures for the first 2 frames of the hitcircleoverlay.png animation, thus cutting the approach time down by 1000ms. This makes it only applicable for AR3 or lower, since AR3's approach time is 1440ms, removing 1000ms from this = 440ms, which is roughly the same approach time as AR10. In addition to this, sliders, approach circles and numbers are not animated, and will appear earlier than the circles, cluttering up the playfield and causing more confusion. With all of these factors in mind, the only applicable use of the skin was on maps <=AR3, with no sliders and using invisible numbers and approach circle elements. Since the skin had no real use for ranked maps, the subreddit's community wasn't too concerned about it.

However, it was still possible to only make 1 frame of the animation a blank texture, reducing the AR by 500ms instead of 1000ms. In theory this could make AR5 play like AR8, however the sliderbodies, approach circles and numbers all being unanimated still made the playfield cluttered and hard to read. Recently a player made and released a skin that uses 1 blank animation frame and some clever tricks with darker/black colours to make it more readable (link here).

A couple of weeks ago, it was discovered that a player had been using this skin trick in conjunction with low gamma to make the sliderbodies, defaults and approach circles darker, and thus fit more in line with the approach time of the animated hitcircleoverlay. They uploaded a video of a low AR play which, instead of using an invisible first frame of the animation, it simply used a darker one, which when the gamma is dimmed low enough, becomes invisible. Since this was only noticeable when viewing the video with low gamma, it made for a very convincing liveplay video. After discovering that the skin was animated, the player admitted that they were using it with low gamma to cut the approach time by 500ms, effectively making AR5 play like AR8.2.

I made a comparison video of what they did here, so you can see for yourself the effects:
(had to remove audio due to copyright)

I would consider this as a bug since the animation is limited to only 4 frames of 500ms each, there are many other animations in skinning which can use hundreds or thousands of frames. It seems to me that this was limited to 4 on purpose to prevent its use for manipulation of AR, despite this it is still possible to do so.

Can this animation be permanently removed? Anecdotally I have only ever seen one skin use this for its intended purpose of aesthetic, so removing it would cause little to no problems for people (I think less than 1% of all skins use this, maybe less than 0.1%). Currently it is causing a lot more harm than good

Edit: I think the YouTube embed is broken so you might have to visit here: https://www.youtube.com/watch?v=kI8mv3TJZPM

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Use only the video ID (the part that comes after "v=") when embedding YouTube videos. Fixed it in your post. -VeilStar
blahpy
I agree that this should be removed for sure.
Kondou-Shinichi
inb4 get moved to feature request

yeah please remove this
-GN
Please address this issue.
clayton
patching this won't solve anything; you can achieve a more "realistic" version of this by abusing storyboards too

I'd just wait on the new client since skinning/animations are being re-worked there. maybe we can get some sort of checks in place so that abusive skins like this one will disable score submission
Topic Starter
Mafham
Could the storyboard issue be fixed by verifying that the real storyboard (or lack of) is the one being used, and disable score submission if not?
Dntm8kmeeatu
I requested this be looked at a bit ago, Will poke with another stick.
Nyanaro
I agree with the statements above, AR is an integral part of the game and should not be able to be modified using skin tricks.
blahpy
Bump for visibility, this is a big issue
Dntm8kmeeatu

blahpy wrote:

Bump for visibility, this is a big issue


This has been acknowledged and is being investigated.
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