From 06b14250a6a0d4cd6bd58e120bd91d0ea1bcd501 Mon Sep 17 00:00:00 2001
From: apollo-dw <83023433+apollo-dw@users.noreply.github.com>
Date: Tue, 19 Jul 2022 19:17:16 +0100
Subject: [PATCH] WIP

---
 .../Evaluators/CognitionEvaluator.cs          | 76 +++++++++++++------
 .../Preprocessing/DifficultyHitObject.cs      |  5 ++
 2 files changed, 57 insertions(+), 24 deletions(-)

diff --git a/osu.Game.Rulesets.Osu/Difficulty/Evaluators/CognitionEvaluator.cs b/osu.Game.Rulesets.Osu/Difficulty/Evaluators/CognitionEvaluator.cs
index 8686addbc4..b5cabb06d8 100644
--- a/osu.Game.Rulesets.Osu/Difficulty/Evaluators/CognitionEvaluator.cs
+++ b/osu.Game.Rulesets.Osu/Difficulty/Evaluators/CognitionEvaluator.cs
@@ -2,7 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
-using osu.Framework.Extensions.ObjectExtensions;
+using System.Collections.Generic;
 using osu.Game.Rulesets.Difficulty.Preprocessing;
 using osu.Game.Rulesets.Osu.Difficulty.Preprocessing;
 using osu.Game.Rulesets.Osu.Objects;
@@ -19,32 +19,22 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Evaluators
             var currObj = (OsuDifficultyHitObject)current;
             double currVelocity = currObj.LazyJumpDistance / currObj.StrainTime;
 
+            List<DifficultyHitObject> pastVisibleObjects = retrievePastVisibleObjects(currObj);
+            List<DifficultyHitObject> currentVisibleObjects = retrieveCurrentVisibleObjects(currObj);
+
+            // Rather than note density being the number of on-screen objects visible at the current object,
+            // consider it as how many objects the current object has been visible for.
             double noteDensity = 1.0;
 
-            // This loop sucks so much lol.
-            // Will be replaced in conjuction with the "objects with current visible" and the "currently visible objects" lists
-            // Also variable names like opacity and note density don't seem accurate anymore :face_with_monocole:...
-            for (int i = 0; i < 100; i++)
+            double loopOpacity = 1.0;
+            int previousIndex = 0;
+
+            while (loopOpacity > 0)
             {
-                if (currObj.Next(i + 1).IsNull())
-                    break;
-
-                var currLoopObj = (OsuDifficultyHitObject)currObj.Next(i);
-                var nextLoopObj = (OsuDifficultyHitObject)currObj.Next(i + 1);
-
-                double opacity = currLoopObj.OpacityAt(currObj.BaseObject.StartTime, false);
-
-                if (opacity == 0)
-                    break;
-
-                // Small distances means objects may be cheesed, so it doesn't matter whether they are arranged confusingly.
-                opacity *= logistic((currLoopObj.MinimumJumpDistance - 100) / 15);
-
-                // Objects that are arranged in a mostly-linear fashion should be easy to read (such as circles in a stream).
-                if (nextLoopObj.Angle.IsNotNull())
-                    opacity *= 1 - Math.Pow(Math.Sin(0.5 * nextLoopObj.Angle.Value), 5);
-
-                noteDensity += opacity;
+                var loopObj = (OsuDifficultyHitObject)currObj.Previous(previousIndex);
+                loopOpacity = currObj.OpacityAt(loopObj.StartTime, false);
+                noteDensity += loopOpacity;
+                previousIndex++;
             }
 
             double noteDensityDifficulty = Math.Pow(Math.Max(0, noteDensity - 2), 2);
@@ -71,6 +61,44 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Evaluators
             return difficulty;
         }
 
+        // Returns a list of objects that are visible on screen at
+        // the point in time at which the current object becomes visible.
+        private static List<DifficultyHitObject> retrievePastVisibleObjects(OsuDifficultyHitObject current)
+        {
+            List<DifficultyHitObject> objects = new List<DifficultyHitObject>();
+
+            for (int i = 0; i < current.Index; i++)
+            {
+                DifficultyHitObject currentObj = current.Previous(i);
+
+                if (current.OpacityAt(currentObj.StartTime, false) <= 0)
+                    break;
+
+                objects.Add(currentObj);
+            }
+
+            return objects;
+        }
+
+        // Returns a list of objects that are visible on screen at
+        // the point in time at which the current object needs is clicked.
+        private static List<DifficultyHitObject> retrieveCurrentVisibleObjects(OsuDifficultyHitObject current)
+        {
+            List<DifficultyHitObject> objects = new List<DifficultyHitObject>();
+
+            for (int i = 0; i < current.Count; i++)
+            {
+                OsuDifficultyHitObject currentObj = (OsuDifficultyHitObject)current.Next(i);
+
+                if (currentObj.OpacityAt(current.StartTime, false) <= 0)
+                    break;
+
+                objects.Add(currentObj);
+            }
+
+            return objects;
+        }
+
         private static double logistic(double x) => 1 / (1 + Math.Pow(Math.E, -x));
     }
 }
diff --git a/osu.Game/Rulesets/Difficulty/Preprocessing/DifficultyHitObject.cs b/osu.Game/Rulesets/Difficulty/Preprocessing/DifficultyHitObject.cs
index 9ce0906dea..3da9c5ef0a 100644
--- a/osu.Game/Rulesets/Difficulty/Preprocessing/DifficultyHitObject.cs
+++ b/osu.Game/Rulesets/Difficulty/Preprocessing/DifficultyHitObject.cs
@@ -16,6 +16,11 @@ namespace osu.Game.Rulesets.Difficulty.Preprocessing
     {
         private readonly IReadOnlyList<DifficultyHitObject> difficultyHitObjects;
 
+        /// <summary>
+        /// The index of this <see cref="DifficultyHitObject"/> in the list of all <see cref="DifficultyHitObject"/>s.
+        /// </summary>
+        public int Count => difficultyHitObjects.Count;
+
         /// <summary>
         /// The index of this <see cref="DifficultyHitObject"/> in the list of all <see cref="DifficultyHitObject"/>s.
         /// </summary>