Also add the liquids to the material cache key hash.

library/terrain_library_merger_pcm.cpp

@@ -83,6 +83,31 @@ void TerrainLibraryMergerPCM::_material_cache_get_key(Ref<TerrainChunk> chunk) {
 		}
 	}
 
+	uint8_t *liquid_ch = chunk->channel_get(TerrainChunkDefault::DEFAULT_CHANNEL_LIQUID_TYPE);
+
+	if (liquid_ch) {
+		for (uint32_t i = 0; i < size; ++i) {
+			uint8_t v = liquid_ch[i];
+
+			if (v == 0) {
+				continue;
+			}
+
+			int ssize = surfaces.size();
+			bool found = false;
+			for (uint8_t j = 0; j < ssize; ++j) {
+				if (surfaces[j] == v) {
+					found = true;
+					break;
+				}
+			}
+
+			if (!found) {
+				surfaces.push_back(v);
+			}
+		}
+	}
+
 	if (surfaces.size() == 0) {
 		chunk->material_cache_key_set(0);
 		chunk->material_cache_key_has_set(false);