From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: David Slovikosky <davidslovikosky@gmail.com>
Date: Tue, 9 Jun 2020 00:10:03 -0700
Subject: [PATCH] Fix missing chunks due to integer overflow

This patch fixes a bug in the EndIslandDensityFunction class where the distance
from 0,0 squared overflows the maximum size of an integer. The overflow leads
to hard chunk borders around 370,000 blocks from 0,0. After this cutoff there
is a few hundred thousand block gap before end land resuming to generate at
530,000 blocks from spawn. This is due to the integer flipping back and forth.

The fix for the issue is quite simple, casting chunk coordinates to longs
allows the distance calculation to avoid overflow and work as intended.

This issue is being tracked in Mojira ticket MC-159283

diff --git a/src/main/java/net/minecraft/world/level/levelgen/DensityFunctions.java b/src/main/java/net/minecraft/world/level/levelgen/DensityFunctions.java
index 8a5826d80f9275de1a2a6a2e23369dd1920f560f..6825feea42667a0f14c4c730e5f1ac970c654c56 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/DensityFunctions.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/DensityFunctions.java
@@ -501,7 +501,7 @@ public final class DensityFunctions {
             int l = j / 2;
             int m = i % 2;
             int n = j % 2;
-            float f = 100.0F - Mth.sqrt((float)(i * i + j * j)) * 8.0F;
+            float f = 100.0F - Mth.sqrt((long) i * (long) i + (long) j * (long) j) * 8.0F; // Paper - cast ints to long to avoid integer overflow
             f = Mth.clamp(f, -100.0F, 80.0F);
 
             for(int o = -12; o <= 12; ++o) {