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173 lines
7.3 KiB
C#
173 lines
7.3 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 System.Collections.Generic;
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using System.Linq;
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using osu.Game.Beatmaps;
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using osu.Game.Rulesets.Difficulty;
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using osu.Game.Rulesets.Difficulty.Preprocessing;
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using osu.Game.Rulesets.Difficulty.Skills;
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using osu.Game.Rulesets.Mods;
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using osu.Game.Rulesets.Scoring;
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using osu.Game.Rulesets.Taiko.Difficulty.Preprocessing;
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using osu.Game.Rulesets.Taiko.Difficulty.Skills;
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using osu.Game.Rulesets.Taiko.Mods;
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using osu.Game.Rulesets.Taiko.Objects;
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using osu.Game.Rulesets.Taiko.Scoring;
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namespace osu.Game.Rulesets.Taiko.Difficulty
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{
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public class TaikoDifficultyCalculator : DifficultyCalculator
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{
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private const double rhythm_skill_multiplier = 0.014;
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private const double colour_skill_multiplier = 0.01;
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private const double stamina_skill_multiplier = 0.02;
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public TaikoDifficultyCalculator(Ruleset ruleset, WorkingBeatmap beatmap)
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: base(ruleset, beatmap)
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{
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}
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protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods, double clockRate) => new Skill[]
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{
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new Colour(mods),
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new Rhythm(mods),
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new Stamina(mods, true),
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new Stamina(mods, false),
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};
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protected override Mod[] DifficultyAdjustmentMods => new Mod[]
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{
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new TaikoModDoubleTime(),
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new TaikoModHalfTime(),
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new TaikoModEasy(),
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new TaikoModHardRock(),
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};
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protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate)
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{
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List<TaikoDifficultyHitObject> taikoDifficultyHitObjects = new List<TaikoDifficultyHitObject>();
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for (int i = 2; i < beatmap.HitObjects.Count; i++)
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{
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taikoDifficultyHitObjects.Add(
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new TaikoDifficultyHitObject(
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beatmap.HitObjects[i], beatmap.HitObjects[i - 1], beatmap.HitObjects[i - 2], clockRate, i
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)
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);
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}
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new StaminaCheeseDetector(taikoDifficultyHitObjects).FindCheese();
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return taikoDifficultyHitObjects;
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}
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protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
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{
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if (beatmap.HitObjects.Count == 0)
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return new TaikoDifficultyAttributes { Mods = mods, Skills = skills };
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var colour = (Colour)skills[0];
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var rhythm = (Rhythm)skills[1];
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var staminaRight = (Stamina)skills[2];
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var staminaLeft = (Stamina)skills[3];
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double colourRating = colour.DifficultyValue() * colour_skill_multiplier;
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double rhythmRating = rhythm.DifficultyValue() * rhythm_skill_multiplier;
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double staminaRating = (staminaRight.DifficultyValue() + staminaLeft.DifficultyValue()) * stamina_skill_multiplier;
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double staminaPenalty = simpleColourPenalty(staminaRating, colourRating);
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staminaRating *= staminaPenalty;
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double combinedRating = locallyCombinedDifficulty(colour, rhythm, staminaRight, staminaLeft, staminaPenalty);
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double separatedRating = norm(1.5, colourRating, rhythmRating, staminaRating);
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double starRating = 1.4 * separatedRating + 0.5 * combinedRating;
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starRating = rescale(starRating);
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HitWindows hitWindows = new TaikoHitWindows();
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hitWindows.SetDifficulty(beatmap.BeatmapInfo.BaseDifficulty.OverallDifficulty);
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return new TaikoDifficultyAttributes
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{
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StarRating = starRating,
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Mods = mods,
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StaminaStrain = staminaRating,
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RhythmStrain = rhythmRating,
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ColourStrain = colourRating,
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// Todo: This int cast is temporary to achieve 1:1 results with osu!stable, and should be removed in the future
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GreatHitWindow = (int)hitWindows.WindowFor(HitResult.Great) / clockRate,
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MaxCombo = beatmap.HitObjects.Count(h => h is Hit),
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Skills = skills
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};
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}
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/// <summary>
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/// Calculates the penalty for the stamina skill for maps with low colour difficulty.
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/// </summary>
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/// <remarks>
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/// Some maps (especially converts) can be easy to read despite a high note density.
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/// This penalty aims to reduce the star rating of such maps by factoring in colour difficulty to the stamina skill.
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/// </remarks>
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private double simpleColourPenalty(double staminaDifficulty, double colorDifficulty)
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{
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if (colorDifficulty <= 0) return 0.79 - 0.25;
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return 0.79 - Math.Atan(staminaDifficulty / colorDifficulty - 12) / Math.PI / 2;
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}
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/// <summary>
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/// Returns the <i>p</i>-norm of an <i>n</i>-dimensional vector.
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/// </summary>
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/// <param name="p">The value of <i>p</i> to calculate the norm for.</param>
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/// <param name="values">The coefficients of the vector.</param>
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private double norm(double p, params double[] values) => Math.Pow(values.Sum(x => Math.Pow(x, p)), 1 / p);
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/// <summary>
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/// Returns the partial star rating of the beatmap, calculated using peak strains from all sections of the map.
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/// </summary>
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/// <remarks>
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/// For each section, the peak strains of all separate skills are combined into a single peak strain for the section.
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/// The resulting partial rating of the beatmap is a weighted sum of the combined peaks (higher peaks are weighted more).
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/// </remarks>
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private double locallyCombinedDifficulty(Colour colour, Rhythm rhythm, Stamina staminaRight, Stamina staminaLeft, double staminaPenalty)
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{
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List<double> peaks = new List<double>();
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var colourPeaks = colour.GetCurrentStrainPeaks().ToList();
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var rhythmPeaks = rhythm.GetCurrentStrainPeaks().ToList();
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var staminaRightPeaks = staminaRight.GetCurrentStrainPeaks().ToList();
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var staminaLeftPeaks = staminaLeft.GetCurrentStrainPeaks().ToList();
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for (int i = 0; i < colourPeaks.Count; i++)
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{
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double colourPeak = colourPeaks[i] * colour_skill_multiplier;
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double rhythmPeak = rhythmPeaks[i] * rhythm_skill_multiplier;
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double staminaPeak = (staminaRightPeaks[i] + staminaLeftPeaks[i]) * stamina_skill_multiplier * staminaPenalty;
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peaks.Add(norm(2, colourPeak, rhythmPeak, staminaPeak));
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}
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double difficulty = 0;
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double weight = 1;
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foreach (double strain in peaks.OrderByDescending(d => d))
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{
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difficulty += strain * weight;
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weight *= 0.9;
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}
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return difficulty;
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}
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/// <summary>
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/// Applies a final re-scaling of the star rating to bring maps with recorded full combos below 9.5 stars.
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/// </summary>
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/// <param name="sr">The raw star rating value before re-scaling.</param>
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private double rescale(double sr)
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{
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if (sr < 0) return sr;
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return 10.43 * Math.Log(sr / 8 + 1);
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}
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}
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}
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