osu/osu.Game.Rulesets.Osu/Difficulty/Skills/OsuStrainSkill.cs
2022-06-29 16:10:06 +09:00

74 lines
2.8 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 osu.Game.Rulesets.Difficulty.Skills;
using osu.Game.Rulesets.Mods;
using System.Linq;
using osu.Framework.Utils;
namespace osu.Game.Rulesets.Osu.Difficulty.Skills
{
public abstract class OsuStrainSkill : StrainSkill
{
/// <summary>
/// The default multiplier applied by <see cref="OsuStrainSkill"/> to the final difficulty value after all other calculations.
/// May be overridden via <see cref="DifficultyMultiplier"/>.
/// </summary>
public const double DEFAULT_DIFFICULTY_MULTIPLIER = 1.06;
/// <summary>
/// The number of sections with the highest strains, which the peak strain reductions will apply to.
/// This is done in order to decrease their impact on the overall difficulty of the map for this skill.
/// </summary>
protected virtual int ReducedSectionCount => 10;
/// <summary>
/// The baseline multiplier applied to the section with the biggest strain.
/// </summary>
protected virtual double ReducedStrainBaseline => 0.75;
/// <summary>
/// The final multiplier to be applied to <see cref="DifficultyValue"/> after all other calculations.
/// </summary>
protected virtual double DifficultyMultiplier => DEFAULT_DIFFICULTY_MULTIPLIER;
protected OsuStrainSkill(Mod[] mods)
: base(mods)
{
}
public override double DifficultyValue()
{
double difficulty = 0;
double weight = 1;
// 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.
var peaks = GetCurrentStrainPeaks().Where(p => p > 0);
List<double> strains = peaks.OrderByDescending(d => d).ToList();
// We are reducing the highest strains first to account for extreme difficulty spikes
for (int i = 0; i < Math.Min(strains.Count, ReducedSectionCount); i++)
{
double scale = Math.Log10(Interpolation.Lerp(1, 10, Math.Clamp((float)i / ReducedSectionCount, 0, 1)));
strains[i] *= Interpolation.Lerp(ReducedStrainBaseline, 1.0, scale);
}
// Difficulty is the weighted sum of the highest strains from every section.
// We're sorting from highest to lowest strain.
foreach (double strain in strains.OrderByDescending(d => d))
{
difficulty += strain * weight;
weight *= DecayWeight;
}
return difficulty * DifficultyMultiplier;
}
}
}