Merge pull request #3564 from smoogipoo/tighten-diffcalc-tolerances

Make difficulty calculation closer match osu!stable

osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapProcessor.cs

@@ -10,6 +10,8 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
 {
     public class OsuBeatmapProcessor : BeatmapProcessor
     {
+        private const int stack_distance = 3;
+
         public OsuBeatmapProcessor(IBeatmap beatmap)
             : base(beatmap)
         {
@@ -18,17 +20,21 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
         public override void PostProcess()
         {
             base.PostProcess();
-            applyStacking((Beatmap<OsuHitObject>)Beatmap);
+
+            var osuBeatmap = (Beatmap<OsuHitObject>)Beatmap;
+
+            // Reset stacking
+            foreach (var h in osuBeatmap.HitObjects)
+                h.StackHeight = 0;
+
+            if (Beatmap.BeatmapInfo.BeatmapVersion >= 6)
+                applyStacking(osuBeatmap);
+            else
+                applyStackingOld(osuBeatmap);
         }
 
         private void applyStacking(Beatmap<OsuHitObject> beatmap)
         {
-            const int stack_distance = 3;
-
-            // Reset stacking
-            for (int i = 0; i <= beatmap.HitObjects.Count - 1; i++)
-                beatmap.HitObjects[i].StackHeight = 0;
-
             // Extend the end index to include objects they are stacked on
             int extendedEndIndex = beatmap.HitObjects.Count - 1;
             for (int i = beatmap.HitObjects.Count - 1; i >= 0; i--)
@@ -167,5 +173,40 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
                 }
             }
         }
+
+        private void applyStackingOld(Beatmap<OsuHitObject> beatmap)
+        {
+            for (int i = 0; i < beatmap.HitObjects.Count; i++)
+            {
+                OsuHitObject currHitObject = beatmap.HitObjects[i];
+
+                if (currHitObject.StackHeight != 0 && !(currHitObject is Slider))
+                    continue;
+
+                double startTime = (currHitObject as IHasEndTime)?.EndTime ?? currHitObject.StartTime;
+                int sliderStack = 0;
+
+                for (int j = i + 1; j < beatmap.HitObjects.Count; j++)
+                {
+                    double stackThreshold = beatmap.HitObjects[i].TimePreempt * beatmap.BeatmapInfo.StackLeniency;
+
+                    if (beatmap.HitObjects[j].StartTime - stackThreshold > startTime)
+                        break;
+
+                    if (Vector2Extensions.Distance(beatmap.HitObjects[j].Position, currHitObject.Position) < stack_distance)
+                    {
+                        currHitObject.StackHeight++;
+                        startTime = (beatmap.HitObjects[j] as IHasEndTime)?.EndTime ?? beatmap.HitObjects[i].StartTime;
+                    }
+                    else if (Vector2Extensions.Distance(beatmap.HitObjects[j].Position, currHitObject.EndPosition) < stack_distance)
+                    {
+                        //Case for sliders - bump notes down and right, rather than up and left.
+                        sliderStack++;
+                        beatmap.HitObjects[j].StackHeight -= sliderStack;
+                        startTime = (beatmap.HitObjects[j] as IHasEndTime)?.EndTime ?? beatmap.HitObjects[i].StartTime;
+                    }
+                }
+            }
+        }
     }
 }

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

@@ -38,7 +38,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty
             double sectionLength = section_length * timeRate;
 
             // The first object doesn't generate a strain, so we begin with an incremented section end
-            double currentSectionEnd = 2 * sectionLength;
+            double currentSectionEnd = Math.Ceiling(beatmap.HitObjects.First().StartTime / sectionLength) * sectionLength;
 
             foreach (OsuDifficultyHitObject h in difficultyBeatmap)
             {

osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyBeatmap.cs

@@ -3,6 +3,7 @@
 
 using System.Collections;
 using System.Collections.Generic;
+using System.Linq;
 using osu.Game.Rulesets.Osu.Objects;
 
 namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
@@ -23,8 +24,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
         {
             // Sort OsuHitObjects by StartTime - they are not correctly ordered in some cases.
             // This should probably happen before the objects reach the difficulty calculator.
-            objects.Sort((a, b) => a.StartTime.CompareTo(b.StartTime));
+            difficultyObjects = createDifficultyObjectEnumerator(objects.OrderBy(h => h.StartTime).ToList(), timeRate);
-            difficultyObjects = createDifficultyObjectEnumerator(objects, timeRate);
         }
 
         /// <summary>

osu.Game.Rulesets.Osu/Difficulty/Preprocessing/OsuDifficultyHitObject.cs

@@ -21,15 +21,25 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
         public OsuHitObject BaseObject { get; }
 
         /// <summary>
-        /// Normalized distance from the <see cref="OsuHitObject.StackedPosition"/> of the previous <see cref="OsuDifficultyHitObject"/>.
+        /// Normalized distance from the end position of the previous <see cref="OsuDifficultyHitObject"/> to the start position of this <see cref="OsuDifficultyHitObject"/>.
         /// </summary>
-        public double Distance { get; private set; }
+        public double JumpDistance { get; private set; }
+
+        /// <summary>
+        /// Normalized distance between the start and end position of the previous <see cref="OsuDifficultyHitObject"/>.
+        /// </summary>
+        public double TravelDistance { get; private set; }
 
         /// <summary>
         /// Milliseconds elapsed since the StartTime of the previous <see cref="OsuDifficultyHitObject"/>.
         /// </summary>
         public double DeltaTime { get; private set; }
 
+        /// <summary>
+        /// Milliseconds elapsed since the start time of the previous <see cref="OsuDifficultyHitObject"/>, with a minimum of 50ms.
+        /// </summary>
+        public double StrainTime { get; private set; }
+
         private readonly OsuHitObject lastObject;
         private readonly double timeRate;
 
@@ -51,31 +61,37 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
         private void setDistances()
         {
             // We will scale distances by this factor, so we can assume a uniform CircleSize among beatmaps.
-            double scalingFactor = normalized_radius / BaseObject.Radius;
+            float scalingFactor = normalized_radius / (float)BaseObject.Radius;
             if (BaseObject.Radius < 30)
             {
-                double smallCircleBonus = Math.Min(30 - BaseObject.Radius, 5) / 50;
+                float smallCircleBonus = Math.Min(30 - (float)BaseObject.Radius, 5) / 50;
                 scalingFactor *= 1 + smallCircleBonus;
             }
 
             Vector2 lastCursorPosition = lastObject.StackedPosition;
-            float lastTravelDistance = 0;
 
             var lastSlider = lastObject as Slider;
             if (lastSlider != null)
             {
                 computeSliderCursorPosition(lastSlider);
                 lastCursorPosition = lastSlider.LazyEndPosition ?? lastCursorPosition;
-                lastTravelDistance = lastSlider.LazyTravelDistance;
             }
 
-            Distance = (lastTravelDistance + (BaseObject.StackedPosition - lastCursorPosition).Length) * scalingFactor;
+            // Don't need to jump to reach spinners
+            if (!(BaseObject is Spinner))
+                JumpDistance = (BaseObject.StackedPosition * scalingFactor - lastCursorPosition * scalingFactor).Length;
+
+            // Todo: BUG!!! Last slider's travel distance is considered ONLY IF we ourselves are also a slider!
+            if (BaseObject is Slider)
+                TravelDistance = (lastSlider?.LazyTravelDistance ?? 0) * scalingFactor;
         }
 
         private void setTimingValues()
         {
-            // Every timing inverval is hard capped at the equivalent of 375 BPM streaming speed as a safety measure.
+            DeltaTime = (BaseObject.StartTime - lastObject.StartTime) / timeRate;
-            DeltaTime = Math.Max(50, (BaseObject.StartTime - lastObject.StartTime) / timeRate);
+
+            // Every strain interval is hard capped at the equivalent of 375 BPM streaming speed as a safety measure
+            StrainTime = Math.Max(50, DeltaTime);
         }
 
         private void computeSliderCursorPosition(Slider slider)
@@ -87,8 +103,14 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Preprocessing
             float approxFollowCircleRadius = (float)(slider.Radius * 3);
             var computeVertex = new Action<double>(t =>
             {
+                double progress = ((int)t - (int)slider.StartTime) / (float)(int)slider.SpanDuration;
+                if (progress % 2 > 1)
+                    progress = 1 - progress % 1;
+                else
+                    progress = progress % 1;
+
                 // ReSharper disable once PossibleInvalidOperationException (bugged in current r# version)
-                var diff = slider.StackedPositionAt(t) - slider.LazyEndPosition.Value;
+                var diff = slider.StackedPosition + slider.Curve.PositionAt(progress) - slider.LazyEndPosition.Value;
                 float dist = diff.Length;
 
                 if (dist > approxFollowCircleRadius)

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

@@ -14,6 +14,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
         protected override double SkillMultiplier => 26.25;
         protected override double StrainDecayBase => 0.15;
 
-        protected override double StrainValueOf(OsuDifficultyHitObject current) => Math.Pow(current.Distance, 0.99) / current.DeltaTime;
+        protected override double StrainValueOf(OsuDifficultyHitObject current)
+            => (Math.Pow(current.TravelDistance, 0.99) + Math.Pow(current.JumpDistance, 0.99)) / current.StrainTime;
     }
 }

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

@@ -19,7 +19,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
 
         protected override double StrainValueOf(OsuDifficultyHitObject current)
         {
-            double distance = current.Distance;
+            double distance = current.TravelDistance + current.JumpDistance;
 
             double speedValue;
             if (distance > single_spacing_threshold)
@@ -33,7 +33,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
             else
                 speedValue = 0.95;
 
-            return speedValue / current.DeltaTime;
+            return speedValue / current.StrainTime;
         }
     }
 }

osu.Game/Beatmaps/ControlPoints/TimingControlPoint.cs

@@ -16,7 +16,7 @@ namespace osu.Game.Beatmaps.ControlPoints
         /// <summary>
         /// The beat length at this control point.
         /// </summary>
-        public double BeatLength
+        public virtual double BeatLength
         {
             get => beatLength;
             set => beatLength = MathHelper.Clamp(value, 6, 60000);

osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs

@@ -318,12 +318,12 @@ namespace osu.Game.Beatmaps.Formats
 
                 if (timingChange)
                 {
-                    handleTimingControlPoint(new TimingControlPoint
+                    var controlPoint = CreateTimingControlPoint();
-                    {
+                    controlPoint.Time = time;
-                        Time = time,
+                    controlPoint.BeatLength = beatLength;
-                        BeatLength = beatLength,
+                    controlPoint.TimeSignature = timeSignature;
-                        TimeSignature = timeSignature
+
-                    });
+                    handleTimingControlPoint(controlPoint);
                 }
 
                 handleDifficultyControlPoint(new DifficultyControlPoint
@@ -418,6 +418,8 @@ namespace osu.Game.Beatmaps.Formats
 
         private double getOffsetTime(double time) => time + (ApplyOffsets ? offset : 0);
 
+        protected virtual TimingControlPoint CreateTimingControlPoint() => new TimingControlPoint();
+
         [Flags]
         internal enum EffectFlags
         {

osu.Game/Beatmaps/Formats/LegacyDifficultyCalculatorBeatmapDecoder.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System.Linq;
+using osu.Game.Beatmaps.ControlPoints;
+
+namespace osu.Game.Beatmaps.Formats
+{
+    /// <summary>
+    /// A <see cref="LegacyBeatmapDecoder"/> built for difficulty calculation of legacy <see cref="Beatmap"/>s
+    /// <remarks>
+    /// To use this, the decoder must be registered by the application through <see cref="LegacyDifficultyCalculatorBeatmapDecoder.Register"/>.
+    /// Doing so will override any existing <see cref="Beatmap"/> decoders.
+    /// </remarks>
+    /// </summary>
+    public class LegacyDifficultyCalculatorBeatmapDecoder : LegacyBeatmapDecoder
+    {
+        public LegacyDifficultyCalculatorBeatmapDecoder(int version = LATEST_VERSION)
+            : base(version)
+        {
+            ApplyOffsets = false;
+        }
+
+        public new static void Register()
+        {
+            AddDecoder<Beatmap>(@"osu file format v", m => new LegacyDifficultyCalculatorBeatmapDecoder(int.Parse(m.Split('v').Last())));
+        }
+
+        protected override TimingControlPoint CreateTimingControlPoint()
+            => new LegacyDifficultyCalculatorControlPoint();
+
+        private class LegacyDifficultyCalculatorControlPoint : TimingControlPoint
+        {
+            public override double BeatLength { get; set; } = 1000;
+        }
+    }
+}