From 4a2d0ce9d32eac0df2acb116e6242490b2adf868 Mon Sep 17 00:00:00 2001
From: 12xx12 <44411062+12xx12@users.noreply.github.com>
Date: Fri, 23 Apr 2021 21:00:02 +0200
Subject: Fixing grass not generating below trees (#5199)

* moves the y-Position below the tree on grass generation
---
 src/Generating/FinishGen.cpp | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/Generating/FinishGen.cpp b/src/Generating/FinishGen.cpp
index e9bf69f55..ef4af91c5 100644
--- a/src/Generating/FinishGen.cpp
+++ b/src/Generating/FinishGen.cpp
@@ -542,6 +542,32 @@ void cFinishGenTallGrass::GenFinish(cChunkDesc & a_ChunkDesc)
 				continue;
 			}
 
+			// Walk below trees:
+			auto BlockBelow = a_ChunkDesc.GetBlockType(x, y - 1, z);
+			bool failed = false;  // marker if the search for a valid position was successful
+
+			while (
+				(BlockBelow == E_BLOCK_LEAVES) ||
+				(BlockBelow == E_BLOCK_NEW_LEAVES) ||
+				(BlockBelow == E_BLOCK_LOG) ||
+				(BlockBelow == E_BLOCK_NEW_LOG) ||
+				(BlockBelow == E_BLOCK_AIR)
+			)
+			{
+				y--;
+				if (!cChunkDef::IsValidHeight(y - 1))
+				{
+					failed = true;
+					break;
+				}
+				BlockBelow = a_ChunkDesc.GetBlockType(x, y - 1, z);
+			}
+
+			if (failed)
+			{
+				continue;
+			}
+
 			// Check if long grass can be placed:
 			if (
 				(a_ChunkDesc.GetBlockType(x, y, z) != E_BLOCK_AIR) ||
-- 
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