28 Sep 2022
Changes to osu!taiko Star Rating & Performance Points
by the osu!taiko pp committee

Changes to osu!taiko Star Rating & Performance Points

by the osu!taiko pp committee

It's no secret that osu!taiko star rating is overdue for a rework. Thanks to your responses in the community survey, we are now ready to unveil a series of planned updates and improvements to how difficulty is evaluated in the osu!taiko game mode!

This effort was led by the newly formed osu!taiko pp committee in response to the results of the osu!taiko SR and PP community survey held earlier this year. This group of individuals is responsible for reviewing all changes regarding star rating and performance points in the osu!taiko game mode.

The team is comprised of two parts: vun and -Lawtron- are leading the development of the new rework, whereas mangomizer and Horiiizon are providing the backing for the community organisation and feedback.

Before we proceed, there are a few key terms and ideas to define.

Star rating is designed to be a measure of how difficult a given beatmap is. It does this through mathematically charting various values in a map's construction, such as how densely packed a given portion of a map is with hit objects. These are described as skills as a general term. Three skills are defined for the purpose of evaluating star rating: stamina, rhythm and colour.

Strain is a concept across all game modes that considers how many times and for how long a player is subjected to high-intensity sections within a beatmap. Sections with very high speed, difficulty or other pertaining factors will significantly increase a beatmap's considered strain values.

We will also be using terminology coined by the osu!taiko community to refer to how patterns are placed. d refers to don (red) notes, and k refers to kat (blue) notes. Repeated notes of the same colour are referred to as monos (short for monocolour).

If you would like to know more about the changes posted, or for a more detailed breakdown on the some of the in-development changes, head on over to the osu!taiko rework document. This is a working document, and will periodically be updated with the latest developments from any developers who request their changes to be added to it, via the osu!taiko pp committee.

You can also dive into the code over in the osu!(lazer) GitHub repository.

Release Schedule

Deployment of these changes will as usual, take some time to fully complete. If you are interested in following the progress we recommend you bookmark this page and check back on this section, as it will be updated as forward progress is made.

✅ Star rating updates [2022-09-28]

An initial pass over all beatmaps to update their star ratings. During this period, new scores will potentially be calculated using the updated calculations, and as such will not match older scores. There may be discrepancies in ordering and display between the game client and web site.

✅ Background user total recalculations [2022-09-28 ~ 2022-09-29]

Starting from the user at rank #1 and working outwards, each user's total pp will be recalculated.

During this period, rank history graphs will be frozen. If a user plays, their total pp value will immediately be updated using the correct values for all past scores, but this won't match past scores' display under "Best Performance". As a result, it may seem as if you temporarily gain, lose or fluctuate in rank relative to others.

During this maintenance, the following will also occur:

  • Inactive users (anyone that has not played the game in 3 months) will be delisted.
  • Scores in the "best performance" profile section may look to be out of order, or not visible at all during this phase. This will resolve completely during the reindexing phase listed below.

✅ Re-enabling of global rank history updates [2022-09-29]

Rank history graphs updates will be enabled and updated again. At this point, all users' global leaderboard ranks will be stable going forward.

✅ Reindexing [2022-09-29]

This will fix scores being out of order on profiles, and in some rare cases not being displayed at all.

An insight into the basis of the new rework

The previous set of changes (applied all the way back in 2020!) accounted for several skill areas at once. This made it difficult to collect meaningful feedback on specific skills and led to increased complexity, halting forward development efforts.

This time, we have opted to take a more modular approach by introducing new changes incrementally, in the hopes of being able to fix any reported issues one step at a time. Moving forward, osu!taiko star rating will be receiving continuous updates, placing star rating and performance points in a state of flux, especially over the coming few months.

In the star rating part of this rework, we have focused on "stamina" and "colour" skills, and in the performance points domain, we have made a significant change to how accuracy is calculated and some tweaks to performance point multipliers for specific mods.

Without further ado, let's get into the nitty-gritty of these changes.

Star rating changes

The "stamina" skill

Issues within the old system

The old system assumed a 2-finger kddk full alternating playstyle (i.e. one in which each subsequent hit is always hit by the other hand regardless of colour). This was implemented as two skills — one for the left hand, and one for the right hand. Instead of using note duration for the split skills, it used the duration between two notes that were pressed with the same hand, a term that we describe as note-pair duration.

In addition, tailored and highly subjective nerfs targeting specific patterns were implemented. The best way to describe this is a "cheese detector".

This is something that we have opted to do away with, following the core policy for the all forward changes:

Never assume a specific playstyle or arbitrarily nerf patterns without a strong justification.

The new stamina system

In this section, the keybinds relating to the two colours found within osu!taiko are named k1, k2 and d1, d2.

Instead of assuming a full-alternate playstyle, we assume that each note of the same colour is always alternated. For example, for the pattern kddkddk, we assume the kats will be hit by k1 d1 d2 k2 d1 d2 k1, and the dons will be hit by k1 d1 d2 k2 d1 d2 k2.

The reason for this is to assume the best-case scenario for repeated keystrokes regardless of playstyle. In other words, we aim to approximate the theoretical minimum stamina required to play a given pattern, with any theoretically rollable pattern being rolled.

We can't (feasibly), nor is it desirable to, detect playstyles, so we assume the case that requires the least physical repetition, which is to switch keys each time a colour is to be hit, and as such all other playstyles will be weaker in comparison to the one used in calculations.

The "colour" skill

Issues within the old system

The previous system only detected the frequency of changes between colours and had specific penalties for particular repeated patterns, similar to how stamina was calculated. This led to complex patterns containing large quantities of single-coloured notes not being considered properly in regards to overall strain values.

The new colour system

The new colour system is more aware of different kinds of patterning used in osu!taiko mapping and is far more capable of formulating appropriate difficulty values from them compared to the old system.

In general, the harder it is to describe a pattern, the harder the pattern will be considered. Additionally, the more dense a pattern (or color sequence, as described by the code) is, the harder the algorithm will consider it to be. Patterns that repeat with longer segments between them are also considered more difficult than patterns that repeat closely to one another.

Calculating the final result

Star rating is now based on peak "strain" values incorporating all three skills covered by the algorithm, namely stamina and colour (as well as rhythm in the future). This is a significant change from the previous system, where only strain and individual skill levels were utilised instead.

Peak difficulty splits the map into sections and combines the highest strains of each skill in each section, aiming to catch out particularly demanding moments. The final star rating is a weighted sum of the peak skill sections, including a slight multiplier to scale better.

Previous approaches were tailored towards scaling maps with respect to difficulty names, a path that we will no longer be taking. Star rating should better reflect the actual difficulty of a map at all levels with new changes going forward, starting with this one.

This also means that star rating values for beatmaps where top-end players are almost — but not quite — getting full combo scores will now extend well into the 10 star range, rather than capping out at around 9.5 stars (medal hunters rejoice!).

While the difference doesn't seem like much, the impact of this kind of change can perhaps be better described by the effect it has on performance points, namely that top player syaron105 gains over 6400 total pp as a result.

Changes to performance points

In recent years, top-end scores in osu!taiko haven't seen as much of an increase in raw performance point values as the other game modes, to the tune of being roughly 40% lower overall. In addition, the survey held at the beginning of this year indicated a great preference for re-evaluating the way performance points are calculated.

Previously, performance points in osu!taiko were calculated by summing the "accuracy pp" and "difficulty pp" components of a score together. The following changes should serve to increase these values, make them more relevant to the apparent difficulty of a given map, and improve balance not only between difficulty-increasing mods, but also their difficulty-reducing counterparts.

All of these changes aim to continue the goals outlined in the new star rating rework.

Globally applied changes

The final step of performance points calculation involves applying a simple multiplier to the calculated value, which allows for simple balancing changes between different types of scores.

To begin with, we have made the following changes:

  • The global multiplier has been increased from 1.1x to 1.13x, affecting all scores.
  • The Hidden multiplier has been decreased from 1.10x to 1.075x.
  • Easy now applies a 0.975x multiplier to help address its problematic nature, especially when paired with Double Time.
  • The No Fail multiplier has been removed. osu!taiko uses a different HP system compared to osu!, negating the need for any kind of penalty. This also helps prevent "sandbagging" in lower ranks.

Additionally, the community survey highlighted issues with short maps being either underweighted at a full combo, or overweighted on plays with several misses.

To combat this, misses will now significantly affect difficulty pp on maps with a max combo below 1000, scaling the miss count by a multiplier of 1000 / total successful hits. This may significantly impact plays on shorter maps with a higher miss count, as visualised below.

Effective miss count graph

Changes to difficulty performance point values

The following changes should result in impressive scores on harder beatmaps rewarding more appropriate performance point values. Please note that these changes only affect the difficulty part of performance, which correlates with the star rating value.

Difficulty pp has been adjusted to hugely nerf previously overweighted low-accuracy scores. In technical terms, difficulty pp scales by the square of the accuracy now instead of linearly, as visualised below:

Accuracy scaling graph

We have also made the following changes to mod-specific performance point multipliers:

  • A further Easy multiplier of 0.985x has been added, in addition to the global nerf described above.
  • A new Hard Rock multiplier of 1.05x has been added, as a way to rebalance the changes found within accuracy pp.

Changes to accuracy performance point values

While difficulty pp is straightforward, accuracy pp contained a plethora of issues, both to do with reading-based mods (Hidden and Flashlight) and mods that affect the hit windows of Greats (300s), i.e. Easy, Double Time and Hard Rock.

  • The impact of the size of the Great (300) hit window on accuracy pp has been reduced significantly. This makes pp less dependent on the 'overall difficulty' value of a map as set in the editor, which greatly reduces the issues of low star rating maps with tight hit windows awarding too much pp.
  • Star rating now affects accuracy pp, which replaces most of the previous scaling from the Great hit window. This further supplements the nerfs in accuracy weighting on low star rating scores while buffing high ones, and thus significantly limits abuse of low star rating 3-mod/4-mod scores.
  • An additional Hidden + Flashlight bonus has been added to accuracy pp. As this mod combination requires total memorisation of maps, the bonus scales with map length, rewarding longer maps more as visualised below.

HDFL multiplier graph

Next steps

Future changes will involve rhythm (which hasn't been touched in these changes so far), and the introduction of a "reading" skill, an entirely new concept to osu!taiko performance points calculation, as well as many other large and small-scale changes.

For people eager to dive into the technicalities of these upcoming changes, work-in-progress details are available here. If you would like to give feedback or help contribute, please join the osu!dev Discord server and direct your comments towards the #difficulty-taiko channel. Additionally, the dedicated Performance Points Discord server may be of interest if you wish to further discuss, contribute, or simply observe star rating and performance points development with a plate-sized magnifying glass.

The osu!taiko pp committee would like to give a huge thank you towards osu!taiko community for the heavy amounts of surveying, testing and feedback during the process. Another big thank you goes to spaceman_atlas and smoogipoo for helping to support and review the changes to the code.

While it's been a long wait, we hope that these changes will help you enjoy climbing the ranks, with pp that better reflects the difficulties of the beatmaps you know and love!

—the osu!taiko pp committee

Comments163

ltca pinned

thank you all for everything, this has been the absolute ride of nearly a year of hard work! so proud of the other committee members, and a massive and i mean MASSIVE thanks to the community for your continued support, feedback and playtesting over hundreds of hours. onto bigger and better changes, we got plenty more to hit doors so stay tuned in the coming months!

peppy pinned

osu! these days is a massive system with millions of players and billions of scores. making large scale changes like this happen involves a lot of moving pieces and people. huge props to everyone involved in the new algorithm's design, but even more importantly, those involved in the review process (of the algorithm, code and documentation like this news post).

making proposals is the easy part. getting them understandable to the average user and deploying them correctly is where the difficulty comes from.

other modes will see similar changes over the coming weeks, so stay tuned!

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Tech maps should be more highlighted

this pp system has a problem lmao
looks at new taiko pp record and its SR

this isnt really about the sr stuff but now when i set a play in taiko it wont calculate pp until i set another one and i got a bunch of fcs and i'm not gaining ranks or pp but they show in my top 100?

In the stamina section, an example is given of the algorithm used to go through patterns, it is first said that the last K of the pattern is played with hand 1, but then the same pattern and same note is said to be played with hand 2 at the end; I'd have to assume that the hand 1 example is incorrect, and the hand 2 one was the intended one, since the hand 1 example would tend to imply one more wrist movement compared to the hand 2 example (5 vs 4). Could I have confirmation on that?

zamnnn

am i the only one that lost more than 500pp :skull:

new pp is completely bs. Everything but long streams worth nothing and long repetitive streams are stupidly overpowered. I gained 2300pp and 300rank but feels like I'm a complete idiot

why did I gain 7k ranks from this

pettan pettan tsurupettan

lost all of my 3 star fc's, my 100pp plays and my 1k pp. but still gained 8k ranks XD

+3.5k rank gain 🤑

It's funny. I gained 200pp and 900 ranks from these changes. I've read through this now and think that the changes totally make sense. And yet I can't help but think that the star ratings are less representative than before. Maybe it's just my ego nabbing on me seeing all my five star maps getting reduced to mid-4 star maps or even 3-star maps, and I'm sure I'll eventually get used to it, but still.

11k in Taiko. Naisu. Hopefully the next standard rework isn't too far behind.

Hoipolloi -Tooru-

also waiting for standard update, im expected to gain 100pp

-Tooru- Hoipolloi

It happened :D

Because of this im now in top 30k, thanks lol

the death of tech maps

lmao they buff one of my map's sr 5.72 to 6.06 that only 11mins long without hard pattern.

kevin3333g when playing taiko and got leaderboard pushed: hOlY s**T

i earned 500pp from this what :V

I feel like this change is an overpowered buff for me. Some of my 180 pp-ish plays are now around 250 pp which I think those plays doesn't deserve pp as that much, because they can be played easily for me as ddkk player.

pettan pettan tsurupettan

prayge

ong

i accidentally in top 40k (used to be 65k) in taiko because of this. thanks.

gossun gossun gossun gossun

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pettan pettan tsurupettan

My S rank low pp plays that has been buried by many D rank pp scores are now appeared on top
Also I lost over 75% of the total pp and lost a lot of ranks because of the abundance of D-rank plays (due to my bad tapping)

edit: WTF I just played any maps and gaining 40k ranks after losing 10k before

Indomi-chan sihamhamda47

me too i gained 25k ranks

pettan pettan tsurupettan

goodbye 100pp hello top 20k

pettan pettan tsurupettan

pettan pettan tsurupettan

Ah, so that's why only stamina was reworked. I like this idea of reworking one skill at a time, hopefully it'll make the task easier for y'all to handle and to attempt more frequent little live system tweaks as you suggested in the post. Cheers! ^^

PS: Finally those Ne Obliviscaris maps are now 7* where they belong, whoa

NOOOO MY CONVERT PLAY COLLECTION, first 200+pp tho...

learn pattern 👍🏿

intresting

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