From 98c3f97eea2dccb67f32192ce6b91c208e7e95d7 Mon Sep 17 00:00:00 2001
From: Maximilian Giller <m.giller.dev@gmail.com>
Date: Tue, 24 Jan 2023 07:04:58 +0100
Subject: [PATCH] Huge optimization

---
 common/noise/worleynoise.cpp | 55 ++++++++++++++++++++++++++++--------
 common/noise/worleynoise.h   |  6 ++--
 2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/common/noise/worleynoise.cpp b/common/noise/worleynoise.cpp
index b256c8f..7c8633e 100644
--- a/common/noise/worleynoise.cpp
+++ b/common/noise/worleynoise.cpp
@@ -11,9 +11,25 @@ void WorleyNoise::generateNoise()
 
     // Generate random points
     points.clear();
-    for (int i = 0; i < numberOfPoints * 3; i++)
+    points.reserve(pow(numberOfPoints, 3));
+    for (int x = 0; x < numberOfPoints; x++)
     {
-        points.emplace_back(getRandomPoint());
+        for (int y = 0; y < numberOfPoints; y++)
+        {
+            for (int z = 0; z < numberOfPoints; z++)
+            {
+                Vector3d point = getRandomPoint();
+
+                // Scale and translate into subcell
+                point /= (float) numberOfPoints;
+
+                Vector3d offset = Vector3d(x, y, z);
+                offset /= (float) numberOfPoints;
+                point += offset;
+
+                points[x + y * numberOfPoints + z * numberOfPoints * numberOfPoints] = point;
+            }
+        }
     }
 
     // Generate getNoise map
@@ -28,7 +44,7 @@ void WorleyNoise::generateNoise()
             {
                 Vector3d point = Vector3d(x, y, z);
                 point /= (float) size;
-                setNoise(x, y, z, repeatableDistanceToClosestPoint(point));
+                setNoise(x, y, z, distanceToClosestPoint(point));
             }
         }
     }
@@ -50,7 +66,7 @@ void WorleyNoise::generateNoise()
               << duration.count() << " seconds" << std::endl;
 }
 
-WorleyNoise::WorleyNoise(int size, int numberOfPoints) : numberOfPoints(pow(numberOfPoints, 3)), Noise(size)
+WorleyNoise::WorleyNoise(int size, int numberOfPoints) : numberOfPoints(numberOfPoints), Noise(size)
 {
     // Init random
     std::random_device rd;
@@ -67,8 +83,11 @@ Vector3d WorleyNoise::getRandomPoint()
 
 float WorleyNoise::distanceToClosestPoint(Vector3d point)
 {
+    std::vector<Vector3d> closePoints = getSubcellPoints(point);
+
+    // Iterate over all subcells
     float minDistance = INFINITY;
-    for (Vector3d p: points)
+    for (Vector3d p: closePoints)
     {
         float distance = length(p - point);
         if (distance < minDistance)
@@ -79,22 +98,34 @@ float WorleyNoise::distanceToClosestPoint(Vector3d point)
     return minDistance;
 }
 
-float WorleyNoise::repeatableDistanceToClosestPoint(Vector3d point)
+std::vector<Vector3d> WorleyNoise::getSubcellPoints(Vector3d point)
 {
-    std::set<float> distances;
+    std::vector<Vector3d> closePoints;
 
-    // Move point around to get distance to closest point in all 27 cells
+    point.x = std::floor(point.x * numberOfPoints);
+    point.y = std::floor(point.y * numberOfPoints);
+    point.z = std::floor(point.z * numberOfPoints);
+
+    // Iterate over all subcells
     for (int x = -1; x <= 1; x++)
     {
         for (int y = -1; y <= 1; y++)
         {
             for (int z = -1; z <= 1; z++)
             {
-                Vector3d offsetPoint = point + Vector3d(x, y, z);
-                distances.insert(distanceToClosestPoint(offsetPoint));
+                Vector3d offset = Vector3d(x, y, z);
+                Vector3d subcell = point + offset;
+
+                // Wrap around
+                subcell.x = std::fmod(subcell.x + numberOfPoints, numberOfPoints);
+                subcell.y = std::fmod(subcell.y + numberOfPoints, numberOfPoints);
+                subcell.z = std::fmod(subcell.z + numberOfPoints, numberOfPoints);
+
+                // Get points in subcell
+                int index = subcell.x + subcell.y * numberOfPoints + subcell.z * numberOfPoints * numberOfPoints;
+                closePoints.push_back(points[index]);
             }
         }
     }
-
-    return *std::min_element(distances.begin(), distances.end());
+    return closePoints;
 }
diff --git a/common/noise/worleynoise.h b/common/noise/worleynoise.h
index d3a0768..0bba3ed 100644
--- a/common/noise/worleynoise.h
+++ b/common/noise/worleynoise.h
@@ -14,7 +14,7 @@ public:
 
 protected:
     int numberOfPoints;
-    std::vector<Vector3d> points;   // Points in 3D space in [0, 1]
+    std::vector<Vector3d> points;   // 3D-Array, each cell represents a subcell. There are numberOfPoints^3 subcells.
 
     std::uniform_real_distribution<float> distribution;
     std::mt19937 generator;
@@ -23,9 +23,9 @@ protected:
 
     float distanceToClosestPoint(Vector3d point);
 
-    float repeatableDistanceToClosestPoint(Vector3d point);
-
     void generateNoise();
+
+    std::vector<Vector3d> getSubcellPoints(Vector3d point);
 };