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osu-lazer/osu.Game.Rulesets.Taiko/Difficulty/TaikoDifficultyCalculator.cs
2022-06-17 16:37:17 +09:00

181 lines
7.4 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 System.Collections.Generic;
using System.Linq;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Difficulty;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Difficulty.Skills;
using osu.Game.Rulesets.Mods;
using osu.Game.Rulesets.Scoring;
using osu.Game.Rulesets.Taiko.Difficulty.Preprocessing;
using osu.Game.Rulesets.Taiko.Difficulty.Skills;
using osu.Game.Rulesets.Taiko.Mods;
using osu.Game.Rulesets.Taiko.Objects;
using osu.Game.Rulesets.Taiko.Scoring;
namespace osu.Game.Rulesets.Taiko.Difficulty
{
public class TaikoDifficultyCalculator : DifficultyCalculator
{
private const double rhythm_skill_multiplier = 0.014;
private const double colour_skill_multiplier = 0.01;
private const double stamina_skill_multiplier = 0.021;
public TaikoDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
: base(ruleset, beatmap)
{
}
protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods, double clockRate) => new Skill[]
{
new Colour(mods),
new Rhythm(mods),
new Stamina(mods)
};
protected override Mod[] DifficultyAdjustmentMods => new Mod[]
{
new TaikoModDoubleTime(),
new TaikoModHalfTime(),
new TaikoModEasy(),
new TaikoModHardRock(),
};
protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate)
{
List<DifficultyHitObject> taikoDifficultyHitObjects = new List<DifficultyHitObject>();
for (int i = 2; i < beatmap.HitObjects.Count; i++)
{
taikoDifficultyHitObjects.Add(
new TaikoDifficultyHitObject(
beatmap.HitObjects[i], beatmap.HitObjects[i - 1], beatmap.HitObjects[i - 2], clockRate, taikoDifficultyHitObjects, taikoDifficultyHitObjects.Count
)
);
}
return taikoDifficultyHitObjects;
}
protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
{
if (beatmap.HitObjects.Count == 0)
return new TaikoDifficultyAttributes { Mods = mods };
var colour = (Colour)skills[0];
var rhythm = (Rhythm)skills[1];
var stamina = (Stamina)skills[2];
double colourRating = colour.DifficultyValue() * colour_skill_multiplier;
double rhythmRating = rhythm.DifficultyValue() * rhythm_skill_multiplier;
double staminaRating = stamina.DifficultyValue() * stamina_skill_multiplier;
double staminaPenalty = simpleColourPenalty(staminaRating, colourRating);
staminaRating *= staminaPenalty;
//TODO : This is a temporary fix for the stamina rating of converts, due to their low colour variance.
if (beatmap.BeatmapInfo.Ruleset.OnlineID == 0 && colourRating < 0.05)
{
staminaPenalty *= 0.25;
}
double combinedRating = locallyCombinedDifficulty(colour, rhythm, stamina, staminaPenalty);
double separatedRating = norm(1.5, colourRating, rhythmRating, staminaRating);
double starRating = 1.4 * separatedRating + 0.5 * combinedRating;
starRating = rescale(starRating);
HitWindows hitWindows = new TaikoHitWindows();
hitWindows.SetDifficulty(beatmap.Difficulty.OverallDifficulty);
return new TaikoDifficultyAttributes
{
StarRating = starRating,
Mods = mods,
StaminaDifficulty = staminaRating,
RhythmDifficulty = rhythmRating,
ColourDifficulty = colourRating,
GreatHitWindow = hitWindows.WindowFor(HitResult.Great) / clockRate,
MaxCombo = beatmap.HitObjects.Count(h => h is Hit),
};
}
/// <summary>
/// Calculates the penalty for the stamina skill for maps with low colour difficulty.
/// </summary>
/// <remarks>
/// Some maps (especially converts) can be easy to read despite a high note density.
/// This penalty aims to reduce the star rating of such maps by factoring in colour difficulty to the stamina skill.
/// </remarks>
private double simpleColourPenalty(double staminaDifficulty, double colorDifficulty)
{
if (colorDifficulty <= 0) return 0.79 - 0.25;
return 0.79 - Math.Atan(staminaDifficulty / colorDifficulty - 12) / Math.PI / 2;
}
/// <summary>
/// Returns the <i>p</i>-norm of an <i>n</i>-dimensional vector.
/// </summary>
/// <param name="p">The value of <i>p</i> to calculate the norm for.</param>
/// <param name="values">The coefficients of the vector.</param>
private double norm(double p, params double[] values) => Math.Pow(values.Sum(x => Math.Pow(x, p)), 1 / p);
/// <summary>
/// Returns the partial star rating of the beatmap, calculated using peak strains from all sections of the map.
/// </summary>
/// <remarks>
/// For each section, the peak strains of all separate skills are combined into a single peak strain for the section.
/// The resulting partial rating of the beatmap is a weighted sum of the combined peaks (higher peaks are weighted more).
/// </remarks>
private double locallyCombinedDifficulty(Colour colour, Rhythm rhythm, Stamina stamina, double staminaPenalty)
{
List<double> peaks = new List<double>();
var colourPeaks = colour.GetCurrentStrainPeaks().ToList();
var rhythmPeaks = rhythm.GetCurrentStrainPeaks().ToList();
var staminaPeaks = stamina.GetCurrentStrainPeaks().ToList();
for (int i = 0; i < colourPeaks.Count; i++)
{
double colourPeak = colourPeaks[i] * colour_skill_multiplier;
double rhythmPeak = rhythmPeaks[i] * rhythm_skill_multiplier;
double staminaPeak = staminaPeaks[i] * stamina_skill_multiplier * staminaPenalty;
double peak = norm(2, colourPeak, rhythmPeak, staminaPeak);
// Sections with 0 strain are excluded to avoid worst-case time complexity of the following sort (e.g. /b/2351871).
// These sections will not contribute to the difficulty.
if (peak > 0)
peaks.Add(peak);
}
double difficulty = 0;
double weight = 1;
foreach (double strain in peaks.OrderByDescending(d => d))
{
difficulty += strain * weight;
weight *= 0.9;
}
return difficulty;
}
/// <summary>
/// Applies a final re-scaling of the star rating to bring maps with recorded full combos below 9.5 stars.
/// </summary>
/// <param name="sr">The raw star rating value before re-scaling.</param>
private double rescale(double sr)
{
if (sr < 0) return sr;
return 10.43 * Math.Log(sr / 8 + 1);
}
}
}