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osu-lazer/osu.Game.Rulesets.Osu/Difficulty/Evaluators/RhythmEvaluator.cs
2022-09-07 13:25:35 +01:00

111 lines
5.2 KiB
C#

// 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.
#nullable disable
using System;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Osu.Difficulty.Preprocessing;
using osu.Game.Rulesets.Osu.Objects;
namespace osu.Game.Rulesets.Osu.Difficulty.Evaluators
{
public static class RhythmEvaluator
{
private const int history_time_max = 5000; // 5 seconds of calculatingRhythmBonus max.
private const double rhythm_multiplier = 0.75;
/// <summary>
/// Calculates a rhythm multiplier for the difficulty of the tap associated with historic data of the current <see cref="OsuDifficultyHitObject"/>.
/// </summary>
public static double EvaluateDifficultyOf(DifficultyHitObject current)
{
if (current.BaseObject is Spinner)
return 0;
int previousIslandSize = 0;
double rhythmComplexitySum = 0;
int islandSize = 1;
double startRatio = 0; // store the ratio of the current start of an island to buff for tighter rhythms
bool firstDeltaSwitch = false;
int historicalNoteCount = Math.Min(current.Index, 32);
int rhythmStart = 0;
while (rhythmStart < historicalNoteCount - 2 && current.StartTime - current.Previous(rhythmStart).StartTime < history_time_max)
rhythmStart++;
for (int i = rhythmStart; i > 0; i--)
{
OsuDifficultyHitObject currObj = (OsuDifficultyHitObject)current.Previous(i - 1);
OsuDifficultyHitObject prevObj = (OsuDifficultyHitObject)current.Previous(i);
OsuDifficultyHitObject lastObj = (OsuDifficultyHitObject)current.Previous(i + 1);
double currHistoricalDecay = (history_time_max - (current.StartTime - currObj.StartTime)) / history_time_max; // scales note 0 to 1 from history to now
currHistoricalDecay = Math.Min((double)(historicalNoteCount - i) / historicalNoteCount, currHistoricalDecay); // either we're limited by time or limited by object count.
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.
double windowPenalty = Math.Min(1, Math.Max(0, Math.Abs(prevDelta - currDelta) - currObj.HitWindowGreat * 0.3) / (currObj.HitWindowGreat * 0.3));
windowPenalty = Math.Min(1, windowPenalty);
double effectiveRatio = windowPenalty * currRatio;
if (firstDeltaSwitch)
{
if (!(prevDelta > 1.25 * currDelta || prevDelta * 1.25 < currDelta))
{
if (islandSize < 7)
islandSize++; // island is still progressing, count size.
}
else
{
if (current.Previous(i - 1).BaseObject is Slider) // bpm change is into slider, this is easy acc window
effectiveRatio *= 0.125;
if (current.Previous(i).BaseObject is Slider) // bpm change was from a slider, this is easier typically than circle -> circle
effectiveRatio *= 0.25;
if (previousIslandSize == islandSize) // repeated island size (ex: triplet -> triplet)
effectiveRatio *= 0.25;
if (previousIslandSize % 2 == islandSize % 2) // repeated island polartiy (2 -> 4, 3 -> 5)
effectiveRatio *= 0.50;
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;
rhythmComplexitySum += Math.Sqrt(effectiveRatio * startRatio) * currHistoricalDecay * Math.Sqrt(4 + islandSize) / 2 * Math.Sqrt(4 + previousIslandSize) / 2;
startRatio = effectiveRatio;
previousIslandSize = islandSize; // log the last island size.
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.
islandSize = 1;
}
}
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;
}
}
return Math.Sqrt(4 + rhythmComplexitySum * rhythm_multiplier) / 2; //produces multiplier that can be applied to strain. range [1, infinity) (not really though)
}
}
}