Biome API: Fix absent water decorations and dust, in deep water (#7470)

Previously, the biomemap was 'BIOME_NONE' for a mapchunk column if a
stone surface was not found in it, causing water surface decorations
and water surface dust to fail.

Store the biome ID of the biome calculated at a water surface and add
it to the biomemap if the biomemap is 'BIOME_NONE' for the mapchunk
column. The biome calculated at a stone surface still has priority
for the biomemap entry, as it should.

Edit an incorrect comment.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/mapgen/mg_biome.cpp b/src/mapgen/mg_biome.cpp
index e02eee703..7f717011c 100644
--- a/src/mapgen/mg_biome.cpp
+++ b/src/mapgen/mg_biome.cpp
@@ -194,9 +194,9 @@ BiomeGenOriginal::BiomeGenOriginal(BiomeManager *biomemgr,
 	humidmap = noise_humidity->result;
 
 	biomemap = new biome_t[m_csize.X * m_csize.Z];
-	// Initialise with the ID of the default biome so that cavegen can get
-	// biomes when biome generation (which calculates the biomemap IDs) is
-	// disabled.
+	// Initialise with the ID of 'BIOME_NONE' so that cavegen can get the
+	// fallback biome when biome generation (which calculates the biomemap IDs)
+	// is disabled.
 	memset(biomemap, 0, sizeof(biome_t) * m_csize.X * m_csize.Z);
 }