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101 lines
4.5 KiB
C#
101 lines
4.5 KiB
C#
// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
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// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
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using System;
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using System.Collections.Generic;
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using osu.Game.Rulesets.Osu.Objects;
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using osu.Game.Rulesets.Osu.OsuDifficulty.Preprocessing;
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using osu.Game.Rulesets.Osu.OsuDifficulty.Utils;
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namespace osu.Game.Rulesets.Osu.OsuDifficulty.Skills
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{
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/// <summary>
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/// Used to processes strain values of <see cref="OsuDifficultyHitObject"/>s, keep track of strain levels caused by the processed objects
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/// and to calculate a final difficulty value representing the difficulty of hitting all the processed objects.
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/// </summary>
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public abstract class Skill
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{
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/// <summary>
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/// Strain values are multiplied by this number for the given skill. Used to balance the value of different skills between each other.
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/// </summary>
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protected abstract double SkillMultiplier { get; }
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/// <summary>
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/// Determines how quickly strain decays for the given skill.
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/// For example a value of 0.15 indicates that strain decays to 15% of its original value in one second.
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/// </summary>
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protected abstract double StrainDecayBase { get; }
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/// <summary>
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/// <see cref="OsuDifficultyHitObject"/>s that were processed previously. They can affect the strain values of the following objects.
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/// </summary>
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protected readonly History<OsuDifficultyHitObject> Previous = new History<OsuDifficultyHitObject>(2); // Contained objects not used yet
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private double currentStrain = 1; // We keep track of the strain level at all times throughout the beatmap.
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private double currentSectionPeak = 1; // We also keep track of the peak strain level in the current section.
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private readonly List<double> strainPeaks = new List<double>();
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/// <summary>
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/// Process an <see cref="OsuDifficultyHitObject"/> and update current strain values accordingly.
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/// </summary>
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public void Process(OsuDifficultyHitObject current)
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{
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currentStrain *= strainDecay(current.DeltaTime);
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if (!(current.BaseObject is Spinner))
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currentStrain += StrainValueOf(current) * SkillMultiplier;
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currentSectionPeak = Math.Max(currentStrain, currentSectionPeak);
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Previous.Push(current);
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}
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/// <summary>
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/// Saves the current peak strain level to the list of strain peaks, which will be used to calculate an overall difficulty.
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/// </summary>
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public void SaveCurrentPeak()
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{
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if (Previous.Count > 0)
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strainPeaks.Add(currentSectionPeak);
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}
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/// <summary>
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/// Sets the initial strain level for a new section.
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/// </summary>
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/// <param name="offset">The beginning of the new section in milliseconds</param>
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public void StartNewSectionFrom(double offset)
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{
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// The maximum strain of the new section is not zero by default, strain decays as usual regardless of section boundaries.
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// This means we need to capture the strain level at the beginning of the new section, and use that as the initial peak level.
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if (Previous.Count > 0)
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currentSectionPeak = currentStrain * strainDecay(offset - Previous[0].BaseObject.StartTime);
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}
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/// <summary>
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/// Returns the calculated difficulty value representing all processed <see cref="OsuDifficultyHitObject"/>s.
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/// </summary>
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public double DifficultyValue()
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{
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strainPeaks.Sort((a, b) => b.CompareTo(a)); // Sort from highest to lowest strain.
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double difficulty = 0;
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double weight = 1;
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// Difficulty is the weighted sum of the highest strains from every section.
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foreach (double strain in strainPeaks)
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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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/// Calculates the strain value of an <see cref="OsuDifficultyHitObject"/>. This value is affected by previously processed objects.
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/// </summary>
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protected abstract double StrainValueOf(OsuDifficultyHitObject current);
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private double strainDecay(double ms) => Math.Pow(StrainDecayBase, ms / 1000);
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}
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}
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