From 7f6722e43fcd4aa19a5e3d65a189959714d64d5c Mon Sep 17 00:00:00 2001
From: apollo-dw <83023433+apollo-dw@users.noreply.github.com>
Date: Wed, 15 Sep 2021 11:24:48 +0100
Subject: [PATCH] throw math.max(N, 1) into straintime

---
 .../Preprocessing/OsuDifficultyHitObject.cs     |  8 ++++++++
 osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs  |  6 +++---
 .../Difficulty/Skills/Speed.cs                  | 17 ++++++++---------
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyHitObject.cs b/osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyHitObject.cs
index 609ad4c995..65efe65129 100644
--- a/osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyHitObject.cs
+++ b/osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyHitObject.cs
@@ -16,6 +16,11 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
 
         protected new OsuHitObject BaseObject => (OsuHitObject)base.BaseObject;
 
+        /// <summary>
+        /// Milliseconds elapsed since the start time of the previous <see cref="OsuDifficultyHitObject"/>, with a minimum of 1ms to account for simultaneous <see cref="OsuDifficultyHitObject"/>s.
+        /// </summary>
+        public double StrainTime { get; private set; }
+
         /// <summary>
         /// Normalized distance from the end position of the previous <see cref="OsuDifficultyHitObject"/> to the start position of this <see cref="OsuDifficultyHitObject"/>.
         /// </summary>
@@ -42,6 +47,9 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
             this.lastObject = (OsuHitObject)lastObject;
 
             setDistances();
+
+            // Capped to 1ms to prevent difficulty calculation breaking from simulatenous objects.
+            StrainTime = Math.Max(DeltaTime, 1);
         }
 
         private void setDistances()
diff --git a/osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs b/osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs
index 7467feb009..16a18cbcb9 100644
--- a/osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs
+++ b/osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs
@@ -46,7 +46,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
                         Math.Max(osuPrevious.JumpDistance - scale, 0)
                         * Math.Pow(Math.Sin(osuCurrent.Angle.Value - angle_bonus_begin), 2)
                         * Math.Max(osuCurrent.JumpDistance - scale, 0));
-                    result = 1.4 * applyDiminishingExp(Math.Max(0, angleBonus)) / Math.Max(timing_threshold, osuPrevious.DeltaTime);
+                    result = 1.4 * applyDiminishingExp(Math.Max(0, angleBonus)) / Math.Max(timing_threshold, osuPrevious.StrainTime);
                 }
             }
 
@@ -54,8 +54,8 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
             double travelDistanceExp = applyDiminishingExp(osuCurrent.TravelDistance);
 
             return Math.Max(
-                result + (jumpDistanceExp + travelDistanceExp + Math.Sqrt(travelDistanceExp * jumpDistanceExp)) / Math.Max(osuCurrent.DeltaTime, timing_threshold),
-                (Math.Sqrt(travelDistanceExp * jumpDistanceExp) + jumpDistanceExp + travelDistanceExp) / Math.Max(osuCurrent.DeltaTime, 1)
+                result + (jumpDistanceExp + travelDistanceExp + Math.Sqrt(travelDistanceExp * jumpDistanceExp)) / Math.Max(osuCurrent.StrainTime, timing_threshold),
+                (Math.Sqrt(travelDistanceExp * jumpDistanceExp) + jumpDistanceExp + travelDistanceExp) / osuCurrent.StrainTime
             );
         }
 
diff --git a/osu.Game.Rulesets.Osu/Difficulty/Skills/Speed.cs b/osu.Game.Rulesets.Osu/Difficulty/Skills/Speed.cs
index aefebbe669..b2eacc5c6a 100644
--- a/osu.Game.Rulesets.Osu/Difficulty/Skills/Speed.cs
+++ b/osu.Game.Rulesets.Osu/Difficulty/Skills/Speed.cs
@@ -47,25 +47,24 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
             var osuCurrent = (OsuDifficultyHitObject)current;
 
             double distance = Math.Min(single_spacing_threshold, osuCurrent.TravelDistance + osuCurrent.JumpDistance);
-            double deltaTime = current.DeltaTime;
+            double strainTime = osuCurrent.StrainTime;
 
             double greatWindowFull = greatWindow * 2;
-            double speedWindowRatio = deltaTime / greatWindowFull;
+            double speedWindowRatio = strainTime / greatWindowFull;
 
             // Aim to nerf cheesy rhythms (Very fast consecutive doubles with large deltatimes between)
-            if (Previous.Count > 0 && deltaTime < greatWindowFull && Previous[0].DeltaTime > deltaTime)
+            if (Previous.Count > 0 && strainTime < greatWindowFull && (Previous[0] as OsuDifficultyHitObject).StrainTime > strainTime)
             {
-               
-                deltaTime = Interpolation.Lerp(Previous[0].DeltaTime, deltaTime, speedWindowRatio);
+                strainTime = Interpolation.Lerp(Previous[0].DeltaTime, strainTime, speedWindowRatio);
             }
 
             // Cap deltatime to the OD 300 hitwindow.
             // 0.93 is derived from making sure 260bpm OD8 streams aren't nerfed harshly, 
-            deltaTime /= Math.Clamp(speedWindowRatio / 0.93, 0.92, 1);
+            strainTime /= Math.Clamp(speedWindowRatio / 0.93, 0.92, 1);
 
             double speedBonus = 1.0;
-            if (deltaTime < min_speed_bonus)
-                speedBonus = 1 + Math.Pow((min_speed_bonus - deltaTime) / speed_balancing_factor, 2);
+            if (strainTime < min_speed_bonus)
+                speedBonus = 1 + Math.Pow((min_speed_bonus - strainTime) / speed_balancing_factor, 2);
 
             double angleBonus = 1.0;
 
@@ -86,7 +85,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
             return (1 + (speedBonus - 1) * 0.75)
                 * angleBonus
                 * (0.95 + speedBonus * Math.Pow(distance / single_spacing_threshold, 3.5))
-                / Math.Max(deltaTime, 1);
+                / strainTime;
         }
     }
 }