Fix JuiceStream velocity calculation

osu.Game.Rulesets.Catch.Tests/Editor/TestSceneCatchEditorSaving.cs

@@ -0,0 +1,66 @@
+// 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.Linq;
+using NUnit.Framework;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.Rulesets.Catch.Objects;
+using osu.Game.Rulesets.Catch.UI;
+using osu.Game.Tests.Visual;
+using osuTK;
+using osuTK.Input;
+
+namespace osu.Game.Rulesets.Catch.Tests.Editor
+{
+    public partial class TestSceneCatchEditorSaving : EditorSavingTestScene
+    {
+        protected override Ruleset CreateRuleset() => new CatchRuleset();
+
+        [Test]
+        public void TestCatchJuiceStreamTickCorrect()
+        {
+            AddStep("enter timing mode", () => InputManager.Key(Key.F3));
+            AddStep("add timing point", () => EditorBeatmap.ControlPointInfo.Add(0, new TimingControlPoint()));
+            AddStep("enter compose mode", () => InputManager.Key(Key.F1));
+
+            Vector2 startPoint = Vector2.Zero;
+            float increment = 0;
+
+            AddUntilStep("wait for playfield", () => this.ChildrenOfType<CatchPlayfield>().FirstOrDefault()?.IsLoaded == true);
+            AddStep("move to centre", () =>
+            {
+                var playfield = this.ChildrenOfType<CatchPlayfield>().Single();
+                startPoint = playfield.ScreenSpaceDrawQuad.Centre + new Vector2(0, playfield.ScreenSpaceDrawQuad.Height / 3);
+                increment = playfield.ScreenSpaceDrawQuad.Height / 10;
+                InputManager.MoveMouseTo(startPoint);
+            });
+            AddStep("choose juice stream placing tool", () => InputManager.Key(Key.Number3));
+            AddStep("start placement", () => InputManager.Click(MouseButton.Left));
+
+            AddStep("move to next", () => InputManager.MoveMouseTo(startPoint + new Vector2(2 * increment, -increment)));
+            AddStep("add node", () => InputManager.Click(MouseButton.Left));
+
+            AddStep("move to next", () => InputManager.MoveMouseTo(startPoint + new Vector2(-2 * increment, -2 * increment)));
+            AddStep("add node", () => InputManager.Click(MouseButton.Left));
+
+            AddStep("move to next", () => InputManager.MoveMouseTo(startPoint + new Vector2(0, -3 * increment)));
+            AddStep("end placement", () => InputManager.Click(MouseButton.Right));
+
+            AddUntilStep("juice stream placed", () => EditorBeatmap.HitObjects, () => Has.Count.EqualTo(1));
+
+            int largeDropletCount = 0, tinyDropletCount = 0;
+            AddStep("store droplet count", () =>
+            {
+                largeDropletCount = EditorBeatmap.HitObjects[0].NestedHitObjects.Count(t => t.GetType() == typeof(Droplet));
+                tinyDropletCount = EditorBeatmap.HitObjects[0].NestedHitObjects.Count(t => t.GetType() == typeof(TinyDroplet));
+            });
+
+            SaveEditor();
+            ReloadEditorToSameBeatmap();
+
+            AddAssert("large droplet count is the same", () => EditorBeatmap.HitObjects[0].NestedHitObjects.Count(t => t.GetType() == typeof(Droplet)), () => Is.EqualTo(largeDropletCount));
+            AddAssert("tiny droplet count is the same", () => EditorBeatmap.HitObjects[0].NestedHitObjects.Count(t => t.GetType() == typeof(TinyDroplet)), () => Is.EqualTo(tinyDropletCount));
+        }
+    }
+}

osu.Game.Rulesets.Catch/Beatmaps/CatchBeatmapConverter.cs

@@ -45,7 +45,7 @@ protected override IEnumerable<CatchHitObject> ConvertHitObject(HitObject obj, I
                         LegacyConvertedY = yPositionData?.Y ?? CatchHitObject.DEFAULT_LEGACY_CONVERT_Y,
                         // prior to v8, speed multipliers don't adjust for how many ticks are generated over the same distance.
                         // this results in more (or less) ticks being generated in <v8 maps for the same time duration.
-                        TickDistanceMultiplier = beatmap.BeatmapInfo.BeatmapVersion < 8 ? 1 : ((LegacyControlPointInfo)beatmap.ControlPointInfo).DifficultyPointAt(obj.StartTime).SliderVelocity,
+                        TickDistanceMultiplier = beatmap.BeatmapInfo.BeatmapVersion < 8 ? 1f / ((LegacyControlPointInfo)beatmap.ControlPointInfo).DifficultyPointAt(obj.StartTime).SliderVelocity : 1,
                         SliderVelocityMultiplier = sliderVelocityData?.SliderVelocityMultiplier ?? 1
                     }.Yield();
 

osu.Game.Rulesets.Catch/Objects/JuiceStream.cs

@@ -12,6 +12,7 @@
 using osu.Game.Beatmaps.ControlPoints;
 using osu.Game.Rulesets.Judgements;
 using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Legacy;
 using osu.Game.Rulesets.Objects.Types;
 
 namespace osu.Game.Rulesets.Catch.Objects
@@ -46,16 +47,10 @@ public double SliderVelocityMultiplier
         public double TickDistanceMultiplier = 1;
 
         [JsonIgnore]
-        private double velocityFactor;
+        public double Velocity { get; private set; }
 
         [JsonIgnore]
-        private double tickDistanceFactor;
-
-        [JsonIgnore]
-        public double Velocity => velocityFactor * SliderVelocityMultiplier;
-
-        [JsonIgnore]
-        public double TickDistance => tickDistanceFactor * TickDistanceMultiplier;
+        public double TickDistance { get; private set; }
 
         /// <summary>
         /// The length of one span of this <see cref="JuiceStream"/>.
@@ -68,8 +63,13 @@ protected override void ApplyDefaultsToSelf(ControlPointInfo controlPointInfo, I
 
             TimingControlPoint timingPoint = controlPointInfo.TimingPointAt(StartTime);
 
-            velocityFactor = base_scoring_distance * difficulty.SliderMultiplier / timingPoint.BeatLength;
-            tickDistanceFactor = base_scoring_distance * difficulty.SliderMultiplier / difficulty.SliderTickRate;
+            Velocity = base_scoring_distance * difficulty.SliderMultiplier / LegacyRulesetExtensions.GetPrecisionAdjustedBeatLength(this, timingPoint, CatchRuleset.SHORT_NAME);
+
+            // WARNING: this is intentionally not computed as `BASE_SCORING_DISTANCE * difficulty.SliderMultiplier`
+            // for backwards compatibility reasons (intentionally introducing floating point errors to match stable).
+            double scoringDistance = Velocity * timingPoint.BeatLength;
+
+            TickDistance = scoringDistance / difficulty.SliderTickRate * TickDistanceMultiplier;
         }
 
         protected override void CreateNestedHitObjects(CancellationToken cancellationToken)