Clean up off-by-one offsets from repeat-related properties

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

@@ -21,9 +21,7 @@ namespace osu.Game.Rulesets.Catch.Objects
         /// </summary>
         private const float base_scoring_distance = 100;
 
-        public readonly SliderCurve Curve = new SliderCurve();
+        public int RepeatCount { get; set; }
-
-        public int RepeatCount { get; set; } = 1;
 
         public double Velocity;
         public double TickDistance;
@@ -55,7 +53,7 @@ namespace osu.Game.Rulesets.Catch.Objects
 
             var length = Curve.Distance;
             var tickDistance = Math.Min(TickDistance, length);
-            var repeatDuration = length / Velocity;
+            var spanDuration = length / Velocity;
 
             var minDistanceFromEnd = Velocity * 0.01;
 
@@ -67,10 +65,10 @@ namespace osu.Game.Rulesets.Catch.Objects
                 X = X
             });
 
-            for (var repeat = 0; repeat < RepeatCount; repeat++)
+            for (var span = 0; span < this.SpanCount(); span++)
             {
-                var repeatStartTime = StartTime + repeat * repeatDuration;
+                var spanStartTime = StartTime + span * spanDuration;
-                var reversed = repeat % 2 == 1;
+                var reversed = span % 2 == 1;
 
                 for (var d = tickDistance; d <= length; d += tickDistance)
                 {
@@ -80,7 +78,7 @@ namespace osu.Game.Rulesets.Catch.Objects
                     var timeProgress = d / length;
                     var distanceProgress = reversed ? 1 - timeProgress : timeProgress;
 
-                    var lastTickTime = repeatStartTime + timeProgress * repeatDuration;
+                    var lastTickTime = spanStartTime + timeProgress * spanDuration;
                     AddNested(new Droplet
                     {
                         StartTime = lastTickTime,
@@ -95,17 +93,17 @@ namespace osu.Game.Rulesets.Catch.Objects
                     });
                 }
 
-                double tinyTickInterval = tickDistance / length * repeatDuration;
+                double tinyTickInterval = tickDistance / length * spanDuration;
                 while (tinyTickInterval > 100)
                     tinyTickInterval /= 2;
 
-                for (double t = 0; t < repeatDuration; t += tinyTickInterval)
+                for (double t = 0; t < spanDuration; t += tinyTickInterval)
                 {
-                    double progress = reversed ? 1 - t / repeatDuration : t / repeatDuration;
+                    double progress = reversed ? 1 - t / spanDuration : t / spanDuration;
 
                     AddNested(new TinyDroplet
                     {
-                        StartTime = repeatStartTime + t,
+                        StartTime = spanStartTime + t,
                         ComboColour = ComboColour,
                         X = Curve.PositionAt(progress).X / CatchPlayfield.BASE_WIDTH,
                         Samples = new List<SampleInfo>(Samples.Select(s => new SampleInfo
@@ -121,15 +119,15 @@ namespace osu.Game.Rulesets.Catch.Objects
                 {
                     Samples = Samples,
                     ComboColour = ComboColour,
-                    StartTime = repeatStartTime + repeatDuration,
+                    StartTime = spanStartTime + spanDuration,
                     X = Curve.PositionAt(reversed ? 0 : 1).X / CatchPlayfield.BASE_WIDTH
                 });
             }
         }
 
-        public double EndTime => StartTime + RepeatCount * Curve.Distance / Velocity;
+        public double EndTime => StartTime + this.SpanCount() * Curve.Distance / Velocity;
 
-        public float EndX => Curve.PositionAt(ProgressAt(1)).X / CatchPlayfield.BASE_WIDTH;
+        public float EndX => Curve.PositionAt(this.ProgressAt(1)).X / CatchPlayfield.BASE_WIDTH;
 
         public double Duration => EndTime - StartTime;
 
@@ -139,6 +137,8 @@ namespace osu.Game.Rulesets.Catch.Objects
             set { Curve.Distance = value; }
         }
 
+        public SliderCurve Curve { get; } = new SliderCurve();
+
         public List<Vector2> ControlPoints
         {
             get { return Curve.ControlPoints; }
@@ -152,17 +152,5 @@ namespace osu.Game.Rulesets.Catch.Objects
             get { return Curve.CurveType; }
             set { Curve.CurveType = value; }
         }
-
-        public Vector2 PositionAt(double progress) => Curve.PositionAt(ProgressAt(progress));
-
-        public double ProgressAt(double progress)
-        {
-            double p = progress * RepeatCount % 1;
-            if (RepeatAt(progress) % 2 == 1)
-                p = 1 - p;
-            return p;
-        }
-
-        public int RepeatAt(double progress) => (int)(progress * RepeatCount);
     }
 }

osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs

@@ -216,7 +216,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
                 if (curveData == null)
                     return HitObject.Samples;
 
-                double segmentTime = (curveData.EndTime - HitObject.StartTime) / curveData.RepeatCount;
+                double segmentTime = (curveData.EndTime - HitObject.StartTime) / curveData.SpanCount();
 
                 int index = (int)(segmentTime == 0 ? 0 : (time - HitObject.StartTime) / segmentTime);
                 return curveData.RepeatSamples[index];

osu.Game.Rulesets.Mania/Beatmaps/Patterns/Legacy/DistanceObjectPatternGenerator.cs

@@ -25,7 +25,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
 
         private readonly double endTime;
         private readonly double segmentDuration;
-        private readonly int repeatCount;
+        private readonly int spanCount;
 
         private PatternType convertType;
 
@@ -39,25 +39,25 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
             var distanceData = hitObject as IHasDistance;
             var repeatsData = hitObject as IHasRepeats;
 
-            repeatCount = repeatsData?.RepeatCount ?? 1;
+            spanCount = repeatsData?.SpanCount() ?? 1;
 
             TimingControlPoint timingPoint = beatmap.ControlPointInfo.TimingPointAt(hitObject.StartTime);
             DifficultyControlPoint difficultyPoint = beatmap.ControlPointInfo.DifficultyPointAt(hitObject.StartTime);
 
             // The true distance, accounting for any repeats
-            double distance = (distanceData?.Distance ?? 0) * repeatCount;
+            double distance = (distanceData?.Distance ?? 0) * spanCount;
             // The velocity of the osu! hit object - calculated as the velocity of a slider
             double osuVelocity = osu_base_scoring_distance * beatmap.BeatmapInfo.BaseDifficulty.SliderMultiplier * difficultyPoint.SpeedMultiplier / timingPoint.BeatLength;
             // The duration of the osu! hit object
             double osuDuration = distance / osuVelocity;
 
             endTime = hitObject.StartTime + osuDuration;
-            segmentDuration = (endTime - HitObject.StartTime) / repeatCount;
+            segmentDuration = (endTime - HitObject.StartTime) / spanCount;
         }
 
         public override Pattern Generate()
         {
-            if (repeatCount > 1)
+            if (spanCount > 1)
             {
                 if (segmentDuration <= 90)
                     return generateRandomHoldNotes(HitObject.StartTime, 1);
@@ -65,7 +65,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
                 if (segmentDuration <= 120)
                 {
                     convertType |= PatternType.ForceNotStack;
-                    return generateRandomNotes(HitObject.StartTime, repeatCount + 1);
+                    return generateRandomNotes(HitObject.StartTime, spanCount + 1);
                 }
 
                 if (segmentDuration <= 160)
@@ -78,7 +78,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
                 if (duration >= 4000)
                     return generateNRandomNotes(HitObject.StartTime, 0.23, 0, 0);
 
-                if (segmentDuration > 400 && repeatCount < TotalColumns - 1 - RandomStart)
+                if (segmentDuration > 400 && spanCount < TotalColumns - 1 - RandomStart)
                     return generateTiledHoldNotes(HitObject.StartTime);
 
                 return generateHoldAndNormalNotes(HitObject.StartTime);
@@ -212,7 +212,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
             int column = GetColumn((HitObject as IHasXPosition)?.X ?? 0, true);
             bool increasing = Random.NextDouble() > 0.5;
 
-            for (int i = 0; i <= repeatCount; i++)
+            for (int i = 0; i <= spanCount; i++)
             {
                 addToPattern(pattern, column, startTime, startTime);
                 startTime += segmentDuration;
@@ -262,7 +262,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
             int interval = Random.Next(1, TotalColumns - (legacy ? 1 : 0));
 
             int nextColumn = GetColumn((HitObject as IHasXPosition)?.X ?? 0, true);
-            for (int i = 0; i <= repeatCount; i++)
+            for (int i = 0; i <= spanCount; i++)
             {
                 addToPattern(pattern, nextColumn, startTime, startTime);
 
@@ -350,7 +350,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
 
             var pattern = new Pattern();
 
-            int columnRepeat = Math.Min(repeatCount, TotalColumns);
+            int columnRepeat = Math.Min(spanCount, TotalColumns);
 
             int nextColumn = GetColumn((HitObject as IHasXPosition)?.X ?? 0, true);
             if ((convertType & PatternType.ForceNotStack) > 0 && PreviousPattern.ColumnWithObjects < TotalColumns)
@@ -409,7 +409,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
             int nextColumn = Random.Next(RandomStart, TotalColumns);
 
             var rowPattern = new Pattern();
-            for (int i = 0; i <= repeatCount; i++)
+            for (int i = 0; i <= spanCount; i++)
             {
                 if (!(ignoreHead && startTime == HitObject.StartTime))
                 {
@@ -442,7 +442,7 @@ namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
             if (curveData == null)
                 return HitObject.Samples;
 
-            double segmentTime = (endTime - HitObject.StartTime) / repeatCount;
+            double segmentTime = (endTime - HitObject.StartTime) / spanCount;
 
             int index = (int)(segmentTime == 0 ? 0 : (time - HitObject.StartTime) / segmentTime);
             return curveData.RepeatSamples[index];

osu.Game.Rulesets.Osu/Objects/Drawables/DrawableSlider.cs

@@ -10,6 +10,7 @@ using System.Linq;
 using osu.Framework.Graphics.Containers;
 using osu.Game.Rulesets.Osu.Judgements;
 using osu.Framework.Graphics.Primitives;
+using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Rulesets.Scoring;
 
 namespace osu.Game.Rulesets.Osu.Objects.Drawables
@@ -109,7 +110,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
             }
         }
 
-        private int currentRepeat;
+        private int currentSpan;
         public bool Tracking;
 
         protected override void Update()
@@ -120,17 +121,17 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
 
             double progress = MathHelper.Clamp((Time.Current - slider.StartTime) / slider.Duration, 0, 1);
 
-            int repeat = slider.RepeatAt(progress);
+            int span = slider.SpanAt(progress);
             progress = slider.ProgressAt(progress);
 
-            if (repeat > currentRepeat)
+            if (span > currentSpan)
-                currentRepeat = repeat;
+                currentSpan = span;
 
             //todo: we probably want to reconsider this before adding scoring, but it looks and feels nice.
             if (!InitialCircle.Judgements.Any(j => j.IsHit))
                 InitialCircle.Position = slider.Curve.PositionAt(progress);
 
-            foreach (var c in components.OfType<ISliderProgress>()) c.UpdateProgress(progress, repeat);
+            foreach (var c in components.OfType<ISliderProgress>()) c.UpdateProgress(progress, span);
             foreach (var c in components.OfType<ITrackSnaking>()) c.UpdateSnakingPosition(slider.Curve.PositionAt(Body.SnakedStart ?? 0), slider.Curve.PositionAt(Body.SnakedEnd ?? 0));
             foreach (var t in ticks.Children) t.Tracking = Ball.Tracking;
         }

osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBall.cs

@@ -139,7 +139,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
             }
         }
 
-        public void UpdateProgress(double progress, int repeat)
+        public void UpdateProgress(double progress, int span)
         {
             Position = slider.Curve.PositionAt(progress);
         }

osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBody.cs

@@ -15,6 +15,7 @@ using OpenTK;
 using OpenTK.Graphics.ES30;
 using OpenTK.Graphics;
 using osu.Framework.Graphics.Primitives;
+using osu.Game.Rulesets.Objects.Types;
 
 namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
 {
@@ -164,14 +165,14 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
             return true;
         }
 
-        public void UpdateProgress(double progress, int repeat)
+        public void UpdateProgress(double progress, int span)
         {
             double start = 0;
             double end = snakingIn ? MathHelper.Clamp((Time.Current - (slider.StartTime - slider.TimePreempt)) / slider.TimeFadein, 0, 1) : 1;
 
-            if (repeat >= slider.RepeatCount - 1)
+            if (span >= slider.SpanCount() - 1)
             {
-                if (Math.Min(repeat, slider.RepeatCount - 1) % 2 == 1)
+                if (Math.Min(span, slider.SpanCount() - 1) % 2 == 1)
                 {
                     start = 0;
                     end = snakingOut ? progress : 1;

osu.Game.Rulesets.Osu/Objects/ISliderProgress.cs

@@ -5,6 +5,6 @@ namespace osu.Game.Rulesets.Osu.Objects
 {
     public interface ISliderProgress
     {
-        void UpdateProgress(double progress, int repeat);
+        void UpdateProgress(double progress, int span);
     }
 }

osu.Game.Rulesets.Osu/Objects/Slider.cs

@@ -20,12 +20,12 @@ namespace osu.Game.Rulesets.Osu.Objects
         /// </summary>
         private const float base_scoring_distance = 100;
 
-        public readonly SliderCurve Curve = new SliderCurve();
+        public double EndTime => StartTime + this.SpanCount() * Curve.Distance / Velocity;
-
-        public double EndTime => StartTime + RepeatCount * Curve.Distance / Velocity;
         public double Duration => EndTime - StartTime;
 
-        public override Vector2 EndPosition => PositionAt(1);
+        public override Vector2 EndPosition => this.PositionAt(1);
+
+        public SliderCurve Curve { get; } = new SliderCurve();
 
         public List<Vector2> ControlPoints
         {
@@ -58,7 +58,7 @@ namespace osu.Game.Rulesets.Osu.Objects
         internal float LazyTravelDistance;
 
         public List<List<SampleInfo>> RepeatSamples { get; set; } = new List<List<SampleInfo>>();
-        public int RepeatCount { get; set; } = 1;
+        public int RepeatCount { get; set; }
 
         private int stackHeight;
 
@@ -88,18 +88,6 @@ namespace osu.Game.Rulesets.Osu.Objects
             TickDistance = scoringDistance / difficulty.SliderTickRate;
         }
 
-        public Vector2 PositionAt(double progress) => Curve.PositionAt(ProgressAt(progress));
-
-        public double ProgressAt(double progress)
-        {
-            double p = progress * RepeatCount % 1;
-            if (RepeatAt(progress) % 2 == 1)
-                p = 1 - p;
-            return p;
-        }
-
-        public int RepeatAt(double progress) => (int)(progress * RepeatCount);
-
         protected override void CreateNestedHitObjects()
         {
             base.CreateNestedHitObjects();
@@ -114,14 +102,14 @@ namespace osu.Game.Rulesets.Osu.Objects
 
             var length = Curve.Distance;
             var tickDistance = Math.Min(TickDistance, length);
-            var repeatDuration = length / Velocity;
+            var spanDuration = length / Velocity;
 
             var minDistanceFromEnd = Velocity * 0.01;
 
-            for (var repeat = 0; repeat < RepeatCount; repeat++)
+            for (var span = 0; span < this.SpanCount(); span++)
             {
-                var repeatStartTime = StartTime + repeat * repeatDuration;
+                var spanStartTime = StartTime + span * spanDuration;
-                var reversed = repeat % 2 == 1;
+                var reversed = span % 2 == 1;
 
                 for (var d = tickDistance; d <= length; d += tickDistance)
                 {
@@ -144,8 +132,8 @@ namespace osu.Game.Rulesets.Osu.Objects
 
                     AddNested(new SliderTick
                     {
-                        RepeatIndex = repeat,
+                        RepeatIndex = span,
-                        StartTime = repeatStartTime + timeProgress * repeatDuration,
+                        StartTime = spanStartTime + timeProgress * spanDuration,
                         Position = Curve.PositionAt(distanceProgress),
                         StackHeight = StackHeight,
                         Scale = Scale,
@@ -160,7 +148,7 @@ namespace osu.Game.Rulesets.Osu.Objects
         {
             var repeatDuration = Distance / Velocity;
 
-            for (var repeat = 1; repeat < RepeatCount; repeat++)
+            for (var repeat = 1; repeat <= RepeatCount; repeat++)
             {
                 var repeatStartTime = StartTime + repeat * repeatDuration;
 

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Linq;
+using osu.Game.Rulesets.Objects.Types;
 using OpenTK;
 using osu.Game.Rulesets.Osu.Objects;
 

osu.Game.Rulesets.Osu/Tests/TestCaseSlider.cs

@@ -84,14 +84,9 @@ namespace osu.Game.Rulesets.Osu.Tests
 
         private void createSlider(float circleSize = 2, float distance = 400, int repeats = 0, double speedMultiplier = 2)
         {
-            repeats++; // The first run through the slider is considered a repeat
-
             var repeatSamples = new List<List<SampleInfo>>();
-            if (repeats > 1)
+            for (int i = 0; i < repeats; i++)
-            {
+                repeatSamples.Add(new List<SampleInfo>());
-                for (int i = 0; i < repeats; i++)
-                    repeatSamples.Add(new List<SampleInfo>());
-            }
 
             var slider = new Slider
             {

osu.Game.Rulesets.Taiko/Beatmaps/TaikoBeatmapConverter.cs

@@ -84,7 +84,8 @@ namespace osu.Game.Rulesets.Taiko.Beatmaps
 
             if (distanceData != null)
             {
-                int repeats = repeatsData?.RepeatCount ?? 1;
+                // Number of spans of the object - one for the initial length and for each repeat
+                int spans = repeatsData?.SpanCount() ?? 1;
 
                 TimingControlPoint timingPoint = beatmap.ControlPointInfo.TimingPointAt(obj.StartTime);
                 DifficultyControlPoint difficultyPoint = beatmap.ControlPointInfo.DifficultyPointAt(obj.StartTime);
@@ -93,7 +94,7 @@ namespace osu.Game.Rulesets.Taiko.Beatmaps
                 double speedAdjustedBeatLength = timingPoint.BeatLength / speedAdjustment;
 
                 // The true distance, accounting for any repeats. This ends up being the drum roll distance later
-                double distance = distanceData.Distance * repeats * legacy_velocity_multiplier;
+                double distance = distanceData.Distance * spans * legacy_velocity_multiplier;
 
                 // The velocity of the taiko hit object - calculated as the velocity of a drum roll
                 double taikoVelocity = taiko_base_distance * beatmap.BeatmapInfo.BaseDifficulty.SliderMultiplier * legacy_velocity_multiplier / speedAdjustedBeatLength;
@@ -111,7 +112,7 @@ namespace osu.Game.Rulesets.Taiko.Beatmaps
                 double osuDuration = distance / osuVelocity;
 
                 // If the drum roll is to be split into hit circles, assume the ticks are 1/8 spaced within the duration of one beat
-                double tickSpacing = Math.Min(speedAdjustedBeatLength / beatmap.BeatmapInfo.BaseDifficulty.SliderTickRate, taikoDuration / repeats);
+                double tickSpacing = Math.Min(speedAdjustedBeatLength / beatmap.BeatmapInfo.BaseDifficulty.SliderTickRate, taikoDuration / spans);
 
                 if (!isForCurrentRuleset && tickSpacing > 0 && osuDuration < 2 * speedAdjustedBeatLength)
                 {

osu.Game/Rulesets/Objects/Legacy/ConvertHitObjectParser.cs

@@ -77,6 +77,10 @@ namespace osu.Game.Rulesets.Objects.Legacy
                     if (repeatCount > 9000)
                         throw new ArgumentOutOfRangeException(nameof(repeatCount), @"Repeat count is way too high");
 
+                    // osu-stable treated the first span of the slider as a repeat, but no repeats are happening
+                    repeatCount = Math.Max(0, repeatCount - 1);
+
+
                     if (split.Length > 7)
                         length = Convert.ToDouble(split[7], CultureInfo.InvariantCulture);
 
@@ -84,8 +88,7 @@ namespace osu.Game.Rulesets.Objects.Legacy
                         readCustomSampleBanks(split[10], bankInfo);
 
                     // One node for each repeat + the start and end nodes
-                    // Note that the first length of the slider is considered a repeat, but there are no actual repeats happening
+                    int nodes = repeatCount + 2;
-                    int nodes = Math.Max(0, repeatCount - 1) + 2;
 
                     // Populate node sample bank infos with the default hit object sample bank
                     var nodeBankInfos = new List<SampleBankInfo>();
@@ -128,7 +131,7 @@ namespace osu.Game.Rulesets.Objects.Legacy
 
                     // Generate the final per-node samples
                     var nodeSamples = new List<List<SampleInfo>>(nodes);
-                    for (int i = 0; i <= repeatCount; i++)
+                    for (int i = 0; i < nodes; i++)
                         nodeSamples.Add(convertSoundType(nodeSoundTypes[i], nodeBankInfos[i]));
 
                     result = CreateSlider(new Vector2(int.Parse(split[0]), int.Parse(split[1])), combo, points, length, curveType, repeatCount, nodeSamples);

osu.Game/Rulesets/Objects/Legacy/ConvertSlider.cs

@@ -2,7 +2,6 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using osu.Game.Rulesets.Objects.Types;
-using System;
 using System.Collections.Generic;
 using OpenTK;
 using osu.Game.Audio;
@@ -18,34 +17,23 @@ namespace osu.Game.Rulesets.Objects.Legacy
         /// </summary>
         private const float base_scoring_distance = 100;
 
+        /// <summary>
+        /// <see cref="ConvertSlider"/>s don't need a curve since they're converted to ruleset-specific hitobjects.
+        /// </summary>
+        public SliderCurve Curve { get; } = null;
         public List<Vector2> ControlPoints { get; set; }
         public CurveType CurveType { get; set; }
 
         public double Distance { get; set; }
 
         public List<List<SampleInfo>> RepeatSamples { get; set; }
-        public int RepeatCount { get; set; } = 1;
+        public int RepeatCount { get; set; }
 
-        public double EndTime => StartTime + RepeatCount * Distance / Velocity;
+        public double EndTime => StartTime + this.SpanCount() * Distance / Velocity;
         public double Duration => EndTime - StartTime;
 
         public double Velocity = 1;
 
-        public Vector2 PositionAt(double progress)
-        {
-            throw new NotImplementedException();
-        }
-
-        public double ProgressAt(double progress)
-        {
-            throw new NotImplementedException();
-        }
-
-        public int RepeatAt(double progress)
-        {
-            throw new NotImplementedException();
-        }
-
         protected override void ApplyDefaultsToSelf(ControlPointInfo controlPointInfo, BeatmapDifficulty difficulty)
         {
             base.ApplyDefaultsToSelf(controlPointInfo, difficulty);

osu.Game/Rulesets/Objects/Types/IHasCurve.cs

@@ -11,6 +11,11 @@ namespace osu.Game.Rulesets.Objects.Types
     /// </summary>
     public interface IHasCurve : IHasDistance, IHasRepeats
     {
+        /// <summary>
+        /// The curve.
+        /// </summary>
+        SliderCurve Curve { get; }
+
         /// <summary>
         /// The control points that shape the curve.
         /// </summary>
@@ -20,7 +25,10 @@ namespace osu.Game.Rulesets.Objects.Types
         /// The type of curve.
         /// </summary>
         CurveType CurveType { get; }
+    }
 
+    public static class HasCurveExtensions
+    {
         /// <summary>
         /// Computes the position on the curve at a given progress, accounting for repeat logic.
         /// <para>
@@ -28,20 +36,28 @@ namespace osu.Game.Rulesets.Objects.Types
         /// </para>
         /// </summary>
         /// <param name="progress">[0, 1] where 0 is the beginning of the curve and 1 is the end of the curve.</param>
-        Vector2 PositionAt(double progress);
+        public static Vector2 PositionAt(this IHasCurve obj, double progress)
+            => obj.Curve.PositionAt(obj.ProgressAt(progress));
 
         /// <summary>
         /// Finds the progress along the curve, accounting for repeat logic.
         /// </summary>
         /// <param name="progress">[0, 1] where 0 is the beginning of the curve and 1 is the end of the curve.</param>
         /// <returns>[0, 1] where 0 is the beginning of the curve and 1 is the end of the curve.</returns>
-        double ProgressAt(double progress);
+        public static double ProgressAt(this IHasCurve obj, double progress)
+        {
+            double p = progress * obj.SpanCount() % 1;
+            if (obj.SpanAt(progress) % 2 == 1)
+                p = 1 - p;
+            return p;
+        }
 
         /// <summary>
-        /// Determines which repeat of the curve the progress point is on.
+        /// Determines which span of the curve the progress point is on.
         /// </summary>
         /// <param name="progress">[0, 1] where 0 is the beginning of the curve and 1 is the end of the curve.</param>
-        /// <returns>[0, RepeatCount] where 0 is the first run.</returns>
+        /// <returns>[0, SpanCount) where 0 is the first run.</returns>
-        int RepeatAt(double progress);
+        public static int SpanAt(this IHasCurve obj, double progress)
+            => (int)(progress * obj.SpanCount());
     }
 }

osu.Game/Rulesets/Objects/Types/IHasRepeats.cs

@@ -21,4 +21,13 @@ namespace osu.Game.Rulesets.Objects.Types
         /// </summary>
         List<List<SampleInfo>> RepeatSamples { get; }
     }
+
+    public static class HasRepeatsExtensions
+    {
+        /// <summary>
+        /// The amount of times the length of this <see cref="IHasRepeats"/> spans.
+        /// </summary>
+        /// <param name="obj">The object that has repeats.</param>
+        public static int SpanCount(this IHasRepeats obj) => obj.RepeatCount + 1;
+    }
 }