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osu-lazer/osu.Game.Rulesets.Osu/Difficulty/Skills/Speed.cs

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// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
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using System;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Mods;
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using osu.Game.Rulesets.Osu.Difficulty.Preprocessing;
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using osu.Game.Rulesets.Osu.Objects;
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namespace osu.Game.Rulesets.Osu.Difficulty.Skills
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{
/// <summary>
/// Represents the skill required to press keys with regards to keeping up with the speed at which objects need to be hit.
/// </summary>
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public class Speed : OsuStrainSkill
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{
private const double single_spacing_threshold = 125;
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private const double angle_bonus_begin = 5 * Math.PI / 6;
private const double pi_over_4 = Math.PI / 4;
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private const double pi_over_2 = Math.PI / 2;
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private const double rhythm_multiplier = 2.0;
private const int history_time_max = 3000; // 3 seconds of calculatingRhythmBonus max.
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private double skillMultiplier => 1375;
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private double strainDecayBase => 0.3;
private double currentTapStrain = 1;
private double currentMovementStrain = 1;
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private double currentRhythm = 1;
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protected override int ReducedSectionCount => 5;
protected override double DifficultyMultiplier => 1.04;
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private const double min_speed_bonus = 75; // ~200BPM
private const double max_speed_bonus = 45; // ~330BPM
private const double speed_balancing_factor = 40;
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protected override int HistoryLength => 32;
public Speed(Mod[] mods)
: base(mods)
{
}
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private bool isRatioEqual(double ratio, double a, double b)
{
return a + 15 > ratio * b && a - 15 < ratio * b;
}
/// <summary>
/// Calculates a rhythm multiplier for the difficulty of the tap associated with historic data of the current <see cref="OsuDifficultyHitObject"/>.
/// </summary>
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private double calculateRhythmBonus(DifficultyHitObject current)
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{
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if (current.BaseObject is Spinner)
return 0;
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int previousIslandSize = -1;
double rhythmComplexitySum = 0;
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int islandSize = 0;
bool firstDeltaSwitch = false;
for (int i = Previous.Count - 1; i > 0; i--)
{
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double currHistoricalDecay = Math.Max(0, (history_time_max - (current.StartTime - Previous[i - 1].StartTime))) / history_time_max; // scales note 0 to 1 from history to now
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if (currHistoricalDecay != 0)
{
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// below was bugged in initial version. fixed now, but will change values, will do more testing
// currHistoricalDecay = Math.Min(currHistoricalDecay, (double)(Previous.Count - i) / Previous.Count); // either we're limited by time or limited by object count.
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double currDelta = ((OsuDifficultyHitObject)Previous[i - 1]).StrainTime;
double prevDelta = ((OsuDifficultyHitObject)Previous[i]).StrainTime;
double effectiveRatio = Math.Min(prevDelta, currDelta) / Math.Max(prevDelta, currDelta);
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if (effectiveRatio > 0.5)
effectiveRatio = 0.5 + (effectiveRatio - 0.5) * 10; // large buff for 1/3 -> 1/4 type transitions.
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effectiveRatio *= Math.Sqrt(100 / ((currDelta + prevDelta) / 2)) * currHistoricalDecay; // scale with bpm slightly and with time
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if (firstDeltaSwitch)
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{
if (isRatioEqual(1.0, prevDelta, currDelta))
{
islandSize++; // island is still progressing, count size.
}
else
{
if (islandSize > 6)
islandSize = 6;
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if (Previous[i - 1].BaseObject is Slider) // bpm change is into slider, this is easy acc window
effectiveRatio *= 0.25;
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if (Previous[i].BaseObject is Slider) // bpm change was from a slider, this is easier typically than circle -> circle
effectiveRatio *= 0.5;
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if (previousIslandSize == islandSize) // repeated island size (ex: triplet -> triplet)
effectiveRatio *= 0.25;
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rhythmComplexitySum += effectiveRatio;
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previousIslandSize = islandSize; // log the last island size.
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if (prevDelta * 1.25 < currDelta) // we're slowing down, stop counting
firstDeltaSwitch = false; // if we're speeding up, this stays true and we keep counting island size.
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islandSize = 0;
}
}
else if (prevDelta > 1.25 * currDelta) // we want to be speeding up.
{
// Begin counting island until we change speed again.
firstDeltaSwitch = true;
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islandSize = 0;
}
}
}
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return Math.Sqrt(4 + rhythmComplexitySum * rhythm_multiplier) / 2; //produces multiplier that can be applied to strain. range [1, infinity)
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}
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private double tapStrainOf(DifficultyHitObject current, double speedBonus)
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{
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if (current.BaseObject is Spinner)
return 0;
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var osuCurrObj = (OsuDifficultyHitObject)current;
return speedBonus / osuCurrObj.StrainTime;
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}
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private double movementStrainOf(DifficultyHitObject current, double speedBonus)
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{
if (current.BaseObject is Spinner)
return 0;
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var osuCurrObj = (OsuDifficultyHitObject)current;
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double distance = Math.Min(single_spacing_threshold, osuCurrObj.TravelDistance + osuCurrObj.JumpDistance);
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double angleBonus = 1.0;
if (osuCurrObj.Angle != null)
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{
double angle = osuCurrObj.Angle.Value;
if (angle < pi_over_2)
angleBonus = 1.25;
else if (angle < angle_bonus_begin)
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angleBonus = 1 + Math.Pow(Math.Sin(1.5 * (angle_bonus_begin - angle)), 2) / 4;
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}
return (angleBonus * speedBonus * Math.Pow(distance / single_spacing_threshold, 3.5)) / osuCurrObj.StrainTime;
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}
private double strainDecay(double ms) => Math.Pow(strainDecayBase, ms / 1000);
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protected override double CalculateInitialStrain(double time) => (currentMovementStrain + currentTapStrain * currentRhythm) * strainDecay(time - Previous[0].StartTime);
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protected override double StrainValueAt(DifficultyHitObject current)
{
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double speedBonus = 1.0;
double deltaTime = Math.Max(max_speed_bonus, current.DeltaTime);
if (deltaTime < min_speed_bonus)
speedBonus = 1 + 0.75 * Math.Pow((min_speed_bonus - deltaTime) / speed_balancing_factor, 2);
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currentRhythm = calculateRhythmBonus(current);
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currentTapStrain *= strainDecay(current.DeltaTime);
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currentTapStrain += tapStrainOf(current, speedBonus) * skillMultiplier;
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currentMovementStrain *= strainDecay(current.DeltaTime);
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currentMovementStrain += movementStrainOf(current, speedBonus) * skillMultiplier;
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return currentMovementStrain + currentTapStrain * currentRhythm;
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}
}
}