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