Remove combo scaling from Aim and Speed from osu! performance calculation

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyAttributes.cs

@@ -24,6 +24,12 @@ public class OsuDifficultyAttributes : DifficultyAttributes
         [JsonProperty("slider_factor")]
         public double SliderFactor { get; set; }
 
+        [JsonProperty("aim_difficult_strain_count")]
+        public int AimDifficultStrainCount { get; set; }
+
+        [JsonProperty("speed_difficult_strain_count")]
+        public int SpeedDifficultStrainCount { get; set; }
+
         [JsonProperty("approach_rate")]
         public double ApproachRate { get; set; }
 

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyCalculator.cs

@@ -40,6 +40,13 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
 
             double sliderFactor = aimRating > 0 ? aimRatingNoSliders / aimRating : 1;
 
+            int aimDifficultyStrainCount = ((OsuStrainSkill)skills[0]).RelevantDifficultStrains();
+            int speedDifficultyStrainCount = ((OsuStrainSkill)skills[2]).RelevantDifficultStrains();
+
+            // Total number of strains in a map can vary by clockrate, and this needs to be corrected for.
+            aimDifficultyStrainCount = (int)(aimDifficultyStrainCount * clockRate);
+            speedDifficultyStrainCount = (int)(speedDifficultyStrainCount * clockRate);
+
             if (mods.Any(h => h is OsuModRelax))
                 speedRating = 0.0;
 
@@ -78,6 +85,8 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
                 SpeedDifficulty = speedRating,
                 FlashlightDifficulty = flashlightRating,
                 SliderFactor = sliderFactor,
+                AimDifficultStrainCount = aimDifficultyStrainCount,
+                SpeedDifficultStrainCount = speedDifficultyStrainCount,
                 ApproachRate = preempt > 1200 ? (1800 - preempt) / 120 : (1200 - preempt) / 150 + 5,
                 OverallDifficulty = (80 - hitWindowGreat) / 6,
                 DrainRate = drainRate,

osu.Game.Rulesets.Osu/Difficulty/OsuPerformanceCalculator.cs

@@ -95,11 +95,8 @@ private double computeAimValue()
                                  (totalHits > 2000 ? Math.Log10(totalHits / 2000.0) * 0.5 : 0.0);
             aimValue *= lengthBonus;
 
-            // Penalize misses by assessing # of misses relative to the total # of objects. Default a 3% reduction for any # of misses.
             if (effectiveMissCount > 0)
-                aimValue *= 0.97 * Math.Pow(1 - Math.Pow((double)effectiveMissCount / totalHits, 0.775), effectiveMissCount);
-
-            aimValue *= getComboScalingFactor();
+                aimValue *= calculateMissPenalty(effectiveMissCount, Attributes.AimDifficultStrainCount);
 
             double approachRateFactor = 0.0;
             if (Attributes.ApproachRate > 10.33)
@@ -142,11 +139,8 @@ private double computeSpeedValue()
                                  (totalHits > 2000 ? Math.Log10(totalHits / 2000.0) * 0.5 : 0.0);
             speedValue *= lengthBonus;
 
-            // Penalize misses by assessing # of misses relative to the total # of objects. Default a 3% reduction for any # of misses.
             if (effectiveMissCount > 0)
-                speedValue *= 0.97 * Math.Pow(1 - Math.Pow((double)effectiveMissCount / totalHits, 0.775), Math.Pow(effectiveMissCount, .875));
-
-            speedValue *= getComboScalingFactor();
+                speedValue *= calculateMissPenalty(effectiveMissCount, Attributes.SpeedDifficultStrainCount);
 
             double approachRateFactor = 0.0;
             if (Attributes.ApproachRate > 10.33)
@@ -263,6 +257,12 @@ private int calculateEffectiveMissCount()
         }
 
         private double getComboScalingFactor() => Attributes.MaxCombo <= 0 ? 1.0 : Math.Min(Math.Pow(scoreMaxCombo, 0.8) / Math.Pow(Attributes.MaxCombo, 0.8), 1.0);
+
+        private double calculateMissPenalty(double missCount, double strainCount)
+        {
+            return 0.95 / ((missCount / (3 * Math.Sqrt(strainCount))) + 1);
+        }
+
         private int totalHits => countGreat + countOk + countMeh + countMiss;
         private int totalSuccessfulHits => countGreat + countOk + countMeh;
     }

osu.Game.Rulesets.Osu/Difficulty/Skills/OsuStrainSkill.cs

@@ -57,5 +57,12 @@ public override double DifficultyValue()
 
             return difficulty * DifficultyMultiplier;
         }
+
+        public int RelevantDifficultStrains()
+        {
+            List<double> strains = GetCurrentStrainPeaks().OrderByDescending(d => d).ToList();
+
+            return strains.Count(s => s > strains[0] * 0.66);
+        }
     }
 }