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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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using osu.Framework.Utils;
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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 rhythm_multiplier = 0.75;
private const int history_time_max = 5000; // 5 seconds of calculatingRhythmBonus max.
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private const double min_speed_bonus = 75; // ~200BPM
private const double speed_balancing_factor = 40;
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private double skillMultiplier => 1375;
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private double strainDecayBase => 0.3;
private double currentStrain;
private double currentRhythm;
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protected override int ReducedSectionCount => 5;
protected override double DifficultyMultiplier => 1.04;
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protected override int HistoryLength => 32;
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private readonly double greatWindow;
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public Speed(Mod[] mods, double hitWindowGreat)
: base(mods)
{
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greatWindow = hitWindowGreat;
}
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/// <summary>
/// Calculates a rhythm multiplier for the difficulty of the tap associated with historic data of the current <see cref="OsuDifficultyHitObject"/>.
/// </summary>
private double calculateRhythmBonus(DifficultyHitObject current)
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{
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if (current.BaseObject is Spinner)
return 0;
int previousIslandSize = 0;
double rhythmComplexitySum = 0;
int islandSize = 1;
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double startRatio = 0; // store the ratio of the current start of an island to buff for tighter rhythms
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bool firstDeltaSwitch = false;
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int rhythmStart = 0;
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while (rhythmStart < Previous.Count - 2 && current.StartTime - Previous[rhythmStart].StartTime < history_time_max)
rhythmStart++;
for (int i = rhythmStart; i > 0; i--)
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{
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OsuDifficultyHitObject currObj = (OsuDifficultyHitObject)Previous[i - 1];
OsuDifficultyHitObject prevObj = (OsuDifficultyHitObject)Previous[i];
OsuDifficultyHitObject lastObj = (OsuDifficultyHitObject)Previous[i + 1];
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double currHistoricalDecay = (history_time_max - (current.StartTime - currObj.StartTime)) / history_time_max; // scales note 0 to 1 from history to now
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currHistoricalDecay = Math.Min((double)(Previous.Count - i) / Previous.Count, currHistoricalDecay); // either we're limited by time or limited by object count.
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double currDelta = currObj.StrainTime;
double prevDelta = prevObj.StrainTime;
double lastDelta = lastObj.StrainTime;
double currRatio = 1.0 + 6.0 * Math.Min(0.5, Math.Pow(Math.Sin(Math.PI / (Math.Min(prevDelta, currDelta) / Math.Max(prevDelta, currDelta))), 2)); // fancy function to calculate rhythmbonuses.
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double windowPenalty = Math.Min(1, Math.Max(0, Math.Abs(prevDelta - currDelta) - greatWindow * 0.6) / (greatWindow * 0.6));
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windowPenalty = Math.Min(1, windowPenalty);
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double effectiveRatio = windowPenalty * currRatio;
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if (firstDeltaSwitch)
{
if (!(prevDelta > 1.25 * currDelta || prevDelta * 1.25 < currDelta))
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{
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if (islandSize < 7)
islandSize++; // island is still progressing, count size.
}
else
{
if (Previous[i - 1].BaseObject is Slider) // bpm change is into slider, this is easy acc window
effectiveRatio *= 0.125;
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if (Previous[i].BaseObject is Slider) // bpm change was from a slider, this is easier typically than circle -> circle
effectiveRatio *= 0.25;
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if (previousIslandSize == islandSize) // repeated island size (ex: triplet -> triplet)
effectiveRatio *= 0.25;
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if (previousIslandSize % 2 == islandSize % 2) // repeated island polartiy (2 -> 4, 3 -> 5)
effectiveRatio *= 0.50;
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if (lastDelta > prevDelta + 10 && prevDelta > currDelta + 10) // previous increase happened a note ago, 1/1->1/2-1/4, dont want to buff this.
effectiveRatio *= 0.125;
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rhythmComplexitySum += Math.Sqrt(effectiveRatio * startRatio) * currHistoricalDecay * Math.Sqrt(4 + islandSize) / 2 * Math.Sqrt(4 + previousIslandSize) / 2;
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startRatio = 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 = 1;
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}
}
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else if (prevDelta > 1.25 * currDelta) // we want to be speeding up.
{
// Begin counting island until we change speed again.
firstDeltaSwitch = true;
startRatio = effectiveRatio;
islandSize = 1;
}
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}
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return Math.Sqrt(4 + rhythmComplexitySum * rhythm_multiplier) / 2; //produces multiplier that can be applied to strain. range [1, infinity) (not really though)
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}
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private double strainValueOf(DifficultyHitObject current)
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{
if (current.BaseObject is Spinner)
return 0;
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// derive strainTime for calculation
var osuCurrObj = (OsuDifficultyHitObject)current;
var osuPrevObj = Previous.Count > 0 ? (OsuDifficultyHitObject)Previous[0] : null;
double strainTime = osuCurrObj.StrainTime;
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double greatWindowFull = greatWindow * 2;
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double speedWindowRatio = strainTime / greatWindowFull;
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// Aim to nerf cheesy rhythms (Very fast consecutive doubles with large deltatimes between)
if (osuPrevObj != null && strainTime < greatWindowFull && osuPrevObj.StrainTime > strainTime)
strainTime = Interpolation.Lerp(osuPrevObj.StrainTime, strainTime, speedWindowRatio);
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// Cap deltatime to the OD 300 hitwindow.
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// 0.93 is derived from making sure 260bpm OD8 streams aren't nerfed harshly, whilst 0.92 limits the effect of the cap.
strainTime /= Math.Clamp((strainTime / greatWindowFull) / 0.93, 0.92, 1);
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// derive speedBonus for calculation
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double speedBonus = 1.0;
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if (strainTime < min_speed_bonus)
speedBonus = 1 + 0.75 * Math.Pow((min_speed_bonus - strainTime) / speed_balancing_factor, 2);
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double travelDistance = osuPrevObj?.TravelDistance ?? 0;
double distance = Math.Min(single_spacing_threshold, travelDistance + osuCurrObj.MinimumJumpDistance);
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return (speedBonus + speedBonus * Math.Pow(distance / single_spacing_threshold, 3.5)) / strainTime;
}
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private double strainDecay(double ms) => Math.Pow(strainDecayBase, ms / 1000);
protected override double CalculateInitialStrain(double time) => (currentStrain * currentRhythm) * strainDecay(time - Previous[0].StartTime);
protected override double StrainValueAt(DifficultyHitObject current)
{
currentStrain *= strainDecay(current.DeltaTime);
currentStrain += strainValueOf(current) * skillMultiplier;
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currentRhythm = calculateRhythmBonus(current);
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return currentStrain * currentRhythm;
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}
}
}