mirror of https://github.com/ppy/osu
72 lines
2.8 KiB
C#
72 lines
2.8 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 osu.Game.Rulesets.Difficulty.Skills;
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using osu.Game.Rulesets.Mods;
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using System.Linq;
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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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public abstract class OsuStrainSkill : StrainSkill
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{
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/// <summary>
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/// The default multiplier applied by <see cref="OsuStrainSkill"/> to the final difficulty value after all other calculations.
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/// May be overridden via <see cref="DifficultyMultiplier"/>.
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/// </summary>
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public const double DEFAULT_DIFFICULTY_MULTIPLIER = 1.06;
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/// <summary>
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/// The number of sections with the highest strains, which the peak strain reductions will apply to.
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/// This is done in order to decrease their impact on the overall difficulty of the map for this skill.
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/// </summary>
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protected virtual int ReducedSectionCount => 10;
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/// <summary>
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/// The baseline multiplier applied to the section with the biggest strain.
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/// </summary>
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protected virtual double ReducedStrainBaseline => 0.75;
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/// <summary>
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/// The final multiplier to be applied to <see cref="DifficultyValue"/> after all other calculations.
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/// </summary>
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protected virtual double DifficultyMultiplier => DEFAULT_DIFFICULTY_MULTIPLIER;
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protected OsuStrainSkill(Mod[] mods)
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: base(mods)
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{
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}
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public override double DifficultyValue()
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{
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double difficulty = 0;
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double weight = 1;
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// Sections with 0 strain are excluded to avoid worst-case time complexity of the following sort (e.g. /b/2351871).
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// These sections will not contribute to the difficulty.
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var peaks = GetCurrentStrainPeaks().Where(p => p > 0);
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List<double> strains = peaks.OrderDescending().ToList();
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// We are reducing the highest strains first to account for extreme difficulty spikes
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for (int i = 0; i < Math.Min(strains.Count, ReducedSectionCount); i++)
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{
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double scale = Math.Log10(Interpolation.Lerp(1, 10, Math.Clamp((float)i / ReducedSectionCount, 0, 1)));
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strains[i] *= Interpolation.Lerp(ReducedStrainBaseline, 1.0, scale);
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}
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// Difficulty is the weighted sum of the highest strains from every section.
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// We're sorting from highest to lowest strain.
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foreach (double strain in strains.OrderDescending())
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{
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difficulty += strain * weight;
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weight *= DecayWeight;
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}
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return difficulty * DifficultyMultiplier;
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}
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}
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}
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