osu/osu.Game/Rulesets/Scoring/DrainingHealthProcessor.cs

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// 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.
using System;
using System.Collections.Generic;
using System.Linq;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Judgements;
using osu.Game.Rulesets.Objects;
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using osu.Game.Utils;
namespace osu.Game.Rulesets.Scoring
{
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/// <summary>
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/// A <see cref="HealthProcessor"/> which continuously drains health.<br />
/// At HP=0, the minimum health reached for a perfect play is 95%.<br />
/// At HP=5, the minimum health reached for a perfect play is 70%.<br />
/// At HP=10, the minimum health reached for a perfect play is 30%.
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/// </summary>
public class DrainingHealthProcessor : HealthProcessor
{
/// <summary>
/// A reasonable allowable error for the minimum health offset from <see cref="targetMinimumHealth"/>. A 1% error is unnoticeable.
/// </summary>
private const double minimum_health_error = 0.01;
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/// <summary>
/// The minimum health target at an HP drain rate of 0.
/// </summary>
private const double min_health_target = 0.95;
/// <summary>
/// The minimum health target at an HP drain rate of 5.
/// </summary>
private const double mid_health_target = 0.70;
/// <summary>
/// The minimum health target at an HP drain rate of 10.
/// </summary>
private const double max_health_target = 0.30;
private IBeatmap beatmap;
private double gameplayEndTime;
private readonly double drainStartTime;
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private readonly double drainLenience;
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private readonly List<(double time, double health)> healthIncreases = new List<(double, double)>();
private double targetMinimumHealth;
private double drainRate = 1;
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private PeriodTracker noDrainPeriodTracker;
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/// <summary>
/// Creates a new <see cref="DrainingHealthProcessor"/>.
/// </summary>
/// <param name="drainStartTime">The time after which draining should begin.</param>
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/// <param name="drainLenience">A lenience to apply to the default drain rate.<br />
/// A value of 0 uses the default drain rate.<br />
/// A value of 0.5 halves the drain rate.<br />
/// A value of 1 completely removes drain.</param>
public DrainingHealthProcessor(double drainStartTime, double drainLenience = 0)
{
this.drainStartTime = drainStartTime;
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this.drainLenience = drainLenience;
}
protected override void Update()
{
base.Update();
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if (noDrainPeriodTracker?.IsInAny(Time.Current) == true)
return;
// When jumping in and out of gameplay time within a single frame, health should only be drained for the period within the gameplay time
double lastGameplayTime = Math.Clamp(Time.Current - Time.Elapsed, drainStartTime, gameplayEndTime);
double currentGameplayTime = Math.Clamp(Time.Current, drainStartTime, gameplayEndTime);
Health.Value -= drainRate * (currentGameplayTime - lastGameplayTime);
}
public override void ApplyBeatmap(IBeatmap beatmap)
{
this.beatmap = beatmap;
if (beatmap.HitObjects.Count > 0)
gameplayEndTime = beatmap.HitObjects[^1].GetEndTime();
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noDrainPeriodTracker = new PeriodTracker(beatmap.Breaks.Select(breakPeriod => new Period(
beatmap.HitObjects
.Select(hitObject => hitObject.GetEndTime())
.Where(endTime => endTime <= breakPeriod.StartTime)
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.DefaultIfEmpty(double.MinValue)
.Last(),
beatmap.HitObjects
.Select(hitObject => hitObject.StartTime)
.Where(startTime => startTime >= breakPeriod.EndTime)
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.DefaultIfEmpty(double.MaxValue)
.First()
)));
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targetMinimumHealth = BeatmapDifficulty.DifficultyRange(beatmap.BeatmapInfo.BaseDifficulty.DrainRate, min_health_target, mid_health_target, max_health_target);
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// Add back a portion of the amount of HP to be drained, depending on the lenience requested.
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targetMinimumHealth += drainLenience * (1 - targetMinimumHealth);
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// Ensure the target HP is within an acceptable range.
targetMinimumHealth = Math.Clamp(targetMinimumHealth, 0, 1);
base.ApplyBeatmap(beatmap);
}
protected override void ApplyResultInternal(JudgementResult result)
{
base.ApplyResultInternal(result);
if (!result.Type.IsBonus())
healthIncreases.Add((result.HitObject.GetEndTime() + result.TimeOffset, GetHealthIncreaseFor(result)));
}
protected override void Reset(bool storeResults)
{
base.Reset(storeResults);
drainRate = 1;
if (storeResults)
drainRate = computeDrainRate();
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healthIncreases.Clear();
}
private double computeDrainRate()
{
if (healthIncreases.Count <= 1)
return 0;
int adjustment = 1;
double result = 1;
// Although we expect the following loop to converge within 30 iterations (health within 1/2^31 accuracy of the target),
// we'll still keep a safety measure to avoid infinite loops by detecting overflows.
while (adjustment > 0)
{
double currentHealth = 1;
double lowestHealth = 1;
int currentBreak = -1;
for (int i = 0; i < healthIncreases.Count; i++)
{
double currentTime = healthIncreases[i].time;
double lastTime = i > 0 ? healthIncreases[i - 1].time : drainStartTime;
// Subtract any break time from the duration since the last object
if (beatmap.Breaks.Count > 0)
{
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// Advance the last break occuring before the current time
while (currentBreak + 1 < beatmap.Breaks.Count && beatmap.Breaks[currentBreak + 1].EndTime < currentTime)
currentBreak++;
if (currentBreak >= 0)
lastTime = Math.Max(lastTime, beatmap.Breaks[currentBreak].EndTime);
}
// Apply health adjustments
currentHealth -= (healthIncreases[i].time - lastTime) * result;
lowestHealth = Math.Min(lowestHealth, currentHealth);
currentHealth = Math.Min(1, currentHealth + healthIncreases[i].health);
// Common scenario for when the drain rate is definitely too harsh
if (lowestHealth < 0)
break;
}
// Stop if the resulting health is within a reasonable offset from the target
if (Math.Abs(lowestHealth - targetMinimumHealth) <= minimum_health_error)
break;
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// This effectively works like a binary search - each iteration the search space moves closer to the target, but may exceed it.
adjustment *= 2;
result += 1.0 / adjustment * Math.Sign(lowestHealth - targetMinimumHealth);
}
return result;
}
}
}