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209 lines
9.0 KiB
C#
209 lines
9.0 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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using System;
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using osu.Game.Rulesets.Difficulty.Preprocessing;
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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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{
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/// <summary>
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/// Represents the skill required to press keys with regards to keeping up with the speed at which objects need to be hit.
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/// </summary>
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public class Speed : OsuStrainSkill
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{
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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;
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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 = 0.5;
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private const int history_time_max = 5000; // 5 seconds of calculatingRhythmBonus max.
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private double skillMultiplier => 1375;
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private double strainDecayBase => 0.3;
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private double currentTapStrain = 1;
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private double currentMovementStrain = 1;
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private double currentRhythm = 1;
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protected override int ReducedSectionCount => 5;
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protected override double DifficultyMultiplier => 1.04;
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private const double min_speed_bonus = 75; // ~200BPM
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private const double max_speed_bonus = 45;
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private const double speed_balancing_factor = 40;
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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)
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: base(mods)
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{
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greatWindow = hitWindowGreat;
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}
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/// <summary>
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/// Calculates a rhythm multiplier for the difficulty of the tap associated with historic data of the current <see cref="OsuDifficultyHitObject"/>.
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/// </summary>
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private double calculateRhythmBonus(DifficultyHitObject current, double greatWindowFull)
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{
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if (current.BaseObject is Spinner)
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return 0;
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int previousIslandSize = -1;
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double rhythmComplexitySum = 0;
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int islandSize = 0;
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bool firstDeltaSwitch = false;
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for (int i = Previous.Count - 2; i > 0; i--)
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{
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DifficultyHitObject currObj = Previous[i - 1];
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DifficultyHitObject prevObj = Previous[i];
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DifficultyHitObject prevPrevObj = Previous[i + 1];
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double currHistoricalDecay = Math.Max(0, (history_time_max - (current.StartTime - currObj.StartTime))) / history_time_max; // scales note 0 to 1 from history to now
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if (currHistoricalDecay != 0)
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{
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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 = Math.Max(25, currObj.DeltaTime);
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double prevDelta = Math.Max(25, prevObj.DeltaTime);
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double prevPrevDelta = ((OsuDifficultyHitObject)prevPrevObj).StrainTime;
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double effectiveRatio = Math.Min(prevDelta, currDelta) / Math.Max(prevDelta, currDelta);
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if (effectiveRatio > 0.5)
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effectiveRatio = 0.5 + (effectiveRatio - 0.5) * 10; // large buff for 1/3 -> 1/4 type transitions.
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effectiveRatio *= Math.Max(prevDelta, currDelta) / greatWindowFull; // Increase scaling for when hitwindow is large but accuracy range is small.
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effectiveRatio *= currHistoricalDecay; // scale with time
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if (firstDeltaSwitch)
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{
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if (Precision.AlmostEquals(prevDelta, currDelta, 15))
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{
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islandSize++; // island is still progressing, count size.
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}
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else
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{
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if (islandSize > 6)
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islandSize = 6;
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if (Previous[i - 1].BaseObject is Slider) // bpm change is into slider, this is easy acc window
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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
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effectiveRatio *= 0.5;
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if (previousIslandSize == islandSize) // repeated island size (ex: triplet -> triplet)
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effectiveRatio *= 0.25;
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if (prevPrevDelta > prevDelta + 10 && prevDelta > currDelta + 10) // previous increase happened a note ago, 1/1->1/2-1/4, dont want to buff this.
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effectiveRatio *= 0.125;
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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
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firstDeltaSwitch = false; // if we're speeding up, this stays true and we keep counting island size.
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islandSize = 0;
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}
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}
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else if (prevDelta > 1.25 * currDelta) // we want to be speeding up.
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{
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// Begin counting island until we change speed again.
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firstDeltaSwitch = true;
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islandSize = 0;
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}
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}
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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 tapStrainOf(DifficultyHitObject current, double speedBonus, double strainTime)
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{
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if (current.BaseObject is Spinner)
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return 0;
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return speedBonus / strainTime;
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}
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private double movementStrainOf(DifficultyHitObject current, double speedBonus, double strainTime)
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{
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if (current.BaseObject is Spinner)
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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;
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if (osuCurrObj.Angle != null)
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{
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double angle = osuCurrObj.Angle.Value;
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if (angle < pi_over_2)
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angleBonus = 1.25;
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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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}
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return (angleBonus * speedBonus * Math.Pow(distance / single_spacing_threshold, 3.5)) / strainTime;
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}
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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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{
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// derive strainTime for calculation
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var osuCurrObj = (OsuDifficultyHitObject)current;
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var osuPrevObj = Previous.Count > 0 ? (OsuDifficultyHitObject)Previous[0] : null;
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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)
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if (osuPrevObj != null && strainTime < greatWindowFull && osuPrevObj.StrainTime > strainTime)
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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.
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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)
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speedBonus = 1 + 0.75 * Math.Pow((min_speed_bonus - strainTime) / speed_balancing_factor, 2);
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currentRhythm = calculateRhythmBonus(current, greatWindowFull);
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double decay = strainDecay(current.DeltaTime);
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currentTapStrain *= decay;
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currentTapStrain += tapStrainOf(current, speedBonus, strainTime) * skillMultiplier;
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currentMovementStrain *= decay;
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currentMovementStrain += movementStrainOf(current, speedBonus, strainTime) * skillMultiplier;
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return currentMovementStrain + currentTapStrain * currentRhythm;
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}
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}
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}
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