From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: JellySquid <jellysquid+atwork@protonmail.com>
Date: Sat, 26 Sep 2020 14:25:07 -0500
Subject: [PATCH] lithium NoiseChunkGeneratorMixin

Original code by SuperCoder79, licensed under LGPLv3
you can find the original code on https://github.com/jellysquid3/lithium-fabric/ (Yarn mappings)

diff --git a/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java b/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
index 119804e5c12aca3f4fbfeaf424f46152f43b3941..100b53e95eeb9582a629fccf5022a527c07a5f86 100644
--- a/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
+++ b/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
@@ -112,7 +112,15 @@ public final class ChunkGeneratorAbstract extends ChunkGenerator {
         return this.w == i && ((GeneratorSettingBase) this.h.get()).a(resourcekey);
     }
 
+    // Yatopia start
+    private static double sampleOctave(NoiseGeneratorPerlin sampler, double x, double y, double z, double scaledVerticalSize, double scaledY, double frequency) {
+        return sampler.sample(x, y, z, scaledVerticalSize, scaledY) / frequency;
+    }
+    // Yatopia end
+
     private double a(int i, int j, int k, double d0, double d1, double d2, double d3) {
+        // Yatopia start - replaced logic
+        /*
         double d4 = 0.0D;
         double d5 = 0.0D;
         double d6 = 0.0D;
@@ -148,6 +156,83 @@ public final class ChunkGeneratorAbstract extends ChunkGenerator {
         }
 
         return MathHelper.b(d4 / 512.0D, d5 / 512.0D, (d6 / 10.0D + 1.0D) / 2.0D);
+         */
+        double frequency = 1.0;
+        double interpolationValue = 0.0;
+
+        for (int octave = 0; octave < 8; octave++) {
+            double scaledVerticalScale = d3 * frequency;
+            double scaledY = j * scaledVerticalScale;
+
+            interpolationValue += sampleOctave(this.s.a(octave),
+                    NoiseGeneratorOctaves.a(i * d2 * frequency),
+                    NoiseGeneratorOctaves.a(scaledY),
+                    NoiseGeneratorOctaves.a(k * d2 * frequency), scaledVerticalScale, scaledY, frequency);
+
+            frequency /= 2.0;
+        }
+
+        double clampedInterpolation = (interpolationValue / 10.0 + 1.0) / 2.0;
+
+        if (clampedInterpolation >= 1) {
+            // Sample only upper noise, as the lower noise will be interpolated out.
+            frequency = 1.0;
+            double noise = 0.0;
+            for (int octave = 0; octave < 16; octave++) {
+                double scaledVerticalScale = d1 * frequency;
+                double scaledY = j * scaledVerticalScale;
+
+                noise += sampleOctave(this.r.a(octave),
+                        NoiseGeneratorOctaves.a(i * d0 * frequency),
+                        NoiseGeneratorOctaves.a(scaledY),
+                        NoiseGeneratorOctaves.a(k * d0 * frequency), scaledVerticalScale, scaledY, frequency);
+
+                frequency /= 2.0;
+            }
+
+            return noise / 512.0;
+        } else if (clampedInterpolation <= 0) {
+            // Sample only lower noise, as the upper noise will be interpolated out.
+            frequency = 1.0;
+            double noise = 0.0;
+            for (int octave = 0; octave < 16; octave++) {
+                double scaledVerticalScale = d1 * frequency;
+                double scaledY = j * scaledVerticalScale;
+                noise += sampleOctave(this.q.a(octave),
+                        NoiseGeneratorOctaves.a(i * d0 * frequency),
+                        NoiseGeneratorOctaves.a(scaledY),
+                        NoiseGeneratorOctaves.a(k * d0 * frequency), scaledVerticalScale, scaledY, frequency);
+
+                frequency /= 2.0;
+            }
+
+            return noise / 512.0;
+        } else {
+            // [VanillaCopy] SurfaceChunkGenerator#sampleNoise
+            // Sample both and interpolate, as in vanilla.
+
+            frequency = 1.0;
+            double lowerNoise = 0.0;
+            double upperNoise = 0.0;
+
+            for (int octave = 0; octave < 16; octave++) {
+                // Pre calculate these values to share them
+                double scaledVerticalScale = d1 * frequency;
+                double scaledY = j * scaledVerticalScale;
+                double xVal = NoiseGeneratorOctaves.a(i * d0 * frequency);
+                double yVal = NoiseGeneratorOctaves.a(scaledY);
+                double zVal = NoiseGeneratorOctaves.a(k * d0 * frequency);
+
+                upperNoise += sampleOctave(this.r.a(octave), xVal, yVal, zVal, scaledVerticalScale, scaledY, frequency);
+                lowerNoise += sampleOctave(this.q.a(octave), xVal, yVal, zVal, scaledVerticalScale, scaledY, frequency);
+
+                frequency /= 2.0;
+            }
+
+            // Vanilla behavior, return interpolated noise
+            return MathHelper.b(clampedInterpolation, lowerNoise / 512.0, upperNoise / 512.0);
+        }
+        // Yatopia end
     }
 
     private double[] b(int i, int j) {