Difficulty calculation breaks down at very high CS

[Rian8337]

This formula will break down in CS≥85/7, which is approximately 12.14. The situation can be achieved using SC (small circle) mod in combination with HR in high CS maps such as this. When such cases happen, the hitobject radius will be negative.

The original osu! implementation caps the CS at 10 both in gameplay and difficulty calculation.

[None1637]

In https://github.com/osudroid/osu-droid/blob/336ba7f0c98d03e8510cd7d0d7a2a468b097a483/src/ru/nsu/ccfit/zuev/osu/game/GameScene.java#L348 ` scale = (float) ((Config.getRES_HEIGHT() / 480.0f)

• (54.42 - Float.parseFloat(beatmapData.getData("Difficulty", "CircleSize")) * 4.48)
• 2 / GameObjectSize.BASE_OBJECT_SIZE)
• 0.5f * Config.getScaleMultiplier();` //Config.getScaleMultiplier() = (float) ((11 - 5.2450170716245195) / 5) //GameObjectSize.BASE_OBJECT_SIZE = 128 //Config.getRES_HEIGHT() = 720 The max CS of osu!droid in gameplay is approximately 17.62, In this CS, scale is 0. Every time CS+1, the scale reduce 0.105. But EZ mod is scale+0.125, HR is scale-0.125.

[Rian8337]

Should just cap the difficulty calculation part at 10 for feature parity with osu! PC? Or use 85/7 instead?

[None1637]

Should just cap the difficulty calculation part at 10 for feature parity with osu! PC? Or use 85/7 instead?

use 85/7 or 12? But I have a idea is Map CS10-17.62(in game play) to CS10-12.14(in difficulty calculation), and cap the difficulty calculation part to block negative CS

[Rian8337]

use 85/7 or 12? But I have a idea is Map CS10-17.62(in game play) to CS10-12.14(in difficulty calculation), and cap the difficulty calculation part to block negative CS

Actually, we can't use 85/7 since: https://github.com/osudroid/osu-droid/blob/336ba7f0c98d03e8510cd7d0d7a2a468b097a483/src/test/tpdifficulty/tp/tpHitObject.java#L52 This will result in division by zero.

I'm neutral about the mapping part.

[None1637]

use 85/7 or 12? But I have a idea is Map CS10-17.62(in game play) to CS10-12.14(in difficulty calculation), and cap the difficulty calculation part to block negative CS

Actually, we can't use 85/7 since:

https://github.com/osudroid/osu-droid/blob/336ba7f0c98d03e8510cd7d0d7a2a468b097a483/src/test/tpdifficulty/tp/tpHitObject.java#L52

This will result in division by zero.

I'm neutral about the mapping part.

I use 12.14f in my next pr, not 85/7

[Rian8337]

Maybe need to cap gameplay CS at certain threshold too since its increase beyond 17.62 will actually make the circle size bigger instead of smaller. https://github.com/osudroid/osu-droid/blob/336ba7f0c98d03e8510cd7d0d7a2a468b097a483/src/ru/nsu/ccfit/zuev/osu/game/HitCircle.java#L81-L82

[None1637]

Maybe need to cap gameplay CS at certain threshold too since its increase beyond 17.62 will actually make the circle size bigger instead of smaller.

https://github.com/osudroid/osu-droid/blob/336ba7f0c98d03e8510cd7d0d7a2a468b097a483/src/ru/nsu/ccfit/zuev/osu/game/HitCircle.java#L81-L82

Fixed in #89