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osu-lazer/osu.Game.Rulesets.Osu/Difficulty/Evaluators/SpeedEvaluator.cs
2023-06-24 16:07:01 +02:00

66 lines
3.0 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.
using System;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Osu.Difficulty.Preprocessing;
using osu.Game.Rulesets.Osu.Objects;
namespace osu.Game.Rulesets.Osu.Difficulty.Evaluators
{
public static class SpeedEvaluator
{
private const double single_spacing_threshold = 125;
private const double min_speed_bonus = 75; // ~200BPM
private const double speed_balancing_factor = 40;
/// <summary>
/// Evaluates the difficulty of tapping the current object, based on:
/// <list type="bullet">
/// <item><description>time between pressing the previous and current object,</description></item>
/// <item><description>distance between those objects,</description></item>
/// <item><description>and how easily they can be cheesed.</description></item>
/// </list>
/// </summary>
public static double EvaluateDifficultyOf(DifficultyHitObject current)
{
if (current.BaseObject is Spinner)
return 0;
// derive strainTime for calculation
var osuCurrObj = (OsuDifficultyHitObject)current;
var osuPrevObj = current.Index > 0 ? (OsuDifficultyHitObject)current.Previous(0) : null;
var osuNextObj = (OsuDifficultyHitObject?)current.Next(0);
double strainTime = osuCurrObj.StrainTime;
double doubletapness = 1;
// Nerf doubletappable doubles.
if (osuNextObj != null)
{
double currDeltaTime = Math.Max(1, osuCurrObj.DeltaTime);
double nextDeltaTime = Math.Max(1, osuNextObj.DeltaTime);
double deltaDifference = Math.Abs(nextDeltaTime - currDeltaTime);
double speedRatio = currDeltaTime / Math.Max(currDeltaTime, deltaDifference);
double windowRatio = Math.Pow(Math.Min(1, currDeltaTime / osuCurrObj.HitWindowGreat), 2);
doubletapness = Math.Pow(speedRatio, 1 - windowRatio);
}
// Cap deltatime to the OD 300 hitwindow.
// 0.93 is derived from making sure 260bpm OD8 streams aren't nerfed harshly, whilst 0.92 limits the effect of the cap.
strainTime /= Math.Clamp((strainTime / osuCurrObj.HitWindowGreat) / 0.93, 0.92, 1);
// derive speedBonus for calculation
double speedBonus = 1.0;
if (strainTime < min_speed_bonus)
speedBonus = 1 + 0.75 * Math.Pow((min_speed_bonus - strainTime) / speed_balancing_factor, 2);
double travelDistance = osuPrevObj?.TravelDistance ?? 0;
double distance = Math.Min(single_spacing_threshold, travelDistance + osuCurrObj.MinimumJumpDistance);
return (speedBonus + speedBonus * Math.Pow(distance / single_spacing_threshold, 3.5)) * doubletapness / strainTime;
}
}
}