Liquids: Preserve flow state if 'ignore' is a neighbour

Prevent waterfalls from falling down or streams from flowing away when the
source node is in an unloaded block - Nodes near a CONTENT_IGNORE node will
be interpreted as if the ignored node is a liquid node that just supports
the current state of the nodes in question.

diff --git a/src/map.cpp b/src/map.cpp
index 3c135cd4843f151d36086d16c18110131986f6b5..28d650276054cb31a3e5ba6b214b50f6bd6b5699 100644 (file)
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -1309,6 +1309,7 @@ void Map::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks)
                NodeNeighbor neutrals[6]; // nodes that are solid or another kind of liquid
                int num_neutrals = 0;
                bool flowing_down = false;
+               bool ignored_sources = false;
                for (u16 i = 0; i < 6; i++) {
                        NeighborType nt = NEIGHBOR_SAME_LEVEL;
                        switch (i) {
@@ -1336,10 +1337,15 @@ void Map::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks)
                                                        flowing_down = true;
                                        } else {
                                                neutrals[num_neutrals++] = nb;
-                                               // If neutral below is ignore prevent water spreading outwards
-                                               if (nb.t == NEIGHBOR_LOWER &&
-                                                               nb.n.getContent() == CONTENT_IGNORE)
-                                                       flowing_down = true;
+                                               if (nb.n.getContent() == CONTENT_IGNORE) {
+                                                       // If node below is ignore prevent water from
+                                                       // spreading outwards and otherwise prevent from
+                                                       // flowing away as ignore node might be the source
+                                                       if (nb.t == NEIGHBOR_LOWER)
+                                                               flowing_down = true;
+                                                       else
+                                                               ignored_sources = true;
+                                               }
                                        }
                                        break;
                                case LIQUID_SOURCE:
@@ -1392,6 +1398,11 @@ void Map::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks)
                                new_node_content = liquid_kind;
                        else
                                new_node_content = floodable_node;
+               } else if (ignored_sources && liquid_level >= 0) {
+                       // Maybe there are neighbouring sources that aren't loaded yet
+                       // so prevent flowing away.
+                       new_node_level = liquid_level;
+                       new_node_content = liquid_kind;
                } else {
                        // no surrounding sources, so get the maximum level that can flow into this node
                        for (u16 i = 0; i < num_flows; i++) {