Node placement client-side prediction

builtin/item.lua

@@ -342,6 +342,7 @@ minetest.nodedef_default = {
 	usable = false,
 	liquids_pointable = false,
 	tool_capabilities = nil,
+	node_placement_prediction = nil,
 
 	-- Interaction callbacks
 	on_place = redef_wrapper(minetest, 'item_place'), -- minetest.item_place

doc/lua_api.txt

@@ -1100,6 +1100,13 @@ Item definition (register_node, register_craftitem, register_tool)
             choppy={times={[3]=0.90}, maxwear=0.05, maxlevel=0}
         }
     }
+    node_placement_prediction = nil,
+    ^ If nil and item is node, prediction is made automatically
+    ^ If nil and item is not a node, no prediction is made
+    ^ If "" and item is anything, no prediction is made
+    ^ Otherwise should be name of node which the client immediately places
+      on ground when the player places the item. Server will always update
+      actual result to client in a short moment.
 
     on_place = func(itemstack, placer, pointed_thing),
     ^ default: minetest.item_place

src/game.cpp

@@ -2366,8 +2366,41 @@ void the_game(
 				// Otherwise report right click to server
 				else
 				{
+					// Report to server
 					client.interact(3, pointed);
 					camera.setDigging(1);  // right click animation
+					
+					// If the wielded item has node placement prediction,
+					// make that happen
+					const ItemDefinition &def =
+							playeritem.getDefinition(itemdef);
+					if(def.node_placement_prediction != "")
+					do{ // breakable
+						verbosestream<<"Node placement prediction for "
+								<<playeritem.name<<" is "
+								<<def.node_placement_prediction<<std::endl;
+						v3s16 p = neighbourpos;
+						content_t id;
+						bool found =
+							nodedef->getId(def.node_placement_prediction, id);
+						if(!found){
+							errorstream<<"Node placement prediction failed for "
+									<<playeritem.name<<" (places "
+									<<def.node_placement_prediction
+									<<") - Name not known"<<std::endl;
+							break;
+						}
+						MapNode n(id);
+						try{
+							// This triggers the required mesh update too
+							client.addNode(p, n);
+						}catch(InvalidPositionException &e){
+							errorstream<<"Node placement prediction failed for "
+									<<playeritem.name<<" (places "
+									<<def.node_placement_prediction
+									<<") - Position not loaded"<<std::endl;
+						}
+					}while(0);
 				}
 			}
 		}

src/itemdef.cpp

@@ -70,6 +70,7 @@ ItemDefinition& ItemDefinition::operator=(const ItemDefinition &def)
 				*def.tool_capabilities);
 	}
 	groups = def.groups;
+	node_placement_prediction = def.node_placement_prediction;
 #ifndef SERVER
 	inventory_texture = def.inventory_texture;
 	if(def.wield_mesh)
@@ -115,6 +116,8 @@ void ItemDefinition::reset()
 	}
 	groups.clear();
 
+	node_placement_prediction = "";
+	
 #ifndef SERVER
 	inventory_texture = NULL;
 	if(wield_mesh)
@@ -150,6 +153,7 @@ void ItemDefinition::serialize(std::ostream &os) const
 		os<<serializeString(i->first);
 		writeS16(os, i->second);
 	}
+	os<<serializeString(node_placement_prediction);
 }
 
 void ItemDefinition::deSerialize(std::istream &is)
@@ -184,6 +188,11 @@ void ItemDefinition::deSerialize(std::istream &is)
 		int value = readS16(is);
 		groups[name] = value;
 	}
+	// If you add anything here, insert it primarily inside the try-catch
+	// block to not need to increase the version.
+	try{
+		node_placement_prediction = deSerializeString(is);
+	}catch(SerializationError &e) {};
 }
 
 /*

src/itemdef.h

@@ -67,6 +67,11 @@ struct ItemDefinition
 	ToolCapabilities *tool_capabilities;
 	ItemGroupList groups;
 
+	// Client shall immediately place this node when player places the item.
+	// Server will update the precise end result a moment later.
+	// "" = no prediction
+	std::string node_placement_prediction;
+
 	/*
 		Cached stuff
 	*/

src/nodedef.cpp

@@ -633,6 +633,7 @@ public:
 			std::string wrapper = deSerializeString(is2);
 			std::istringstream wrapper_is(wrapper, std::ios::binary);
 			f->deSerialize(wrapper_is);
+			verbosestream<<"deserialized "<<f->name<<std::endl;
 			if(f->name != "")
 				addNameIdMapping(i, f->name);
 		}

src/scriptapi.cpp

@@ -930,13 +930,14 @@ static void read_object_properties(lua_State *L, int index,
 	ItemDefinition
 */
 
-static ItemDefinition read_item_definition(lua_State *L, int index)
+static ItemDefinition read_item_definition(lua_State *L, int index,
+		ItemDefinition default_def = ItemDefinition())
 {
 	if(index < 0)
 		index = lua_gettop(L) + 1 + index;
 
 	// Read the item definition
-	ItemDefinition def;
+	ItemDefinition def = default_def;
 
 	def.type = (ItemType)getenumfield(L, index, "type",
 			es_ItemType, ITEM_NONE);
@@ -981,6 +982,12 @@ static ItemDefinition read_item_definition(lua_State *L, int index)
 	read_groups(L, -1, def.groups);
 	lua_pop(L, 1);
 
+	// Client shall immediately place this node when player places the item.
+	// Server will update the precise end result a moment later.
+	// "" = no prediction
+	getstringfield(L, index, "node_placement_prediction",
+			def.node_placement_prediction);
+
 	return def;
 }
 
@@ -3891,9 +3898,10 @@ static int l_register_item_raw(lua_State *L)
 			get_server(L)->getWritableNodeDefManager();
 
 	// Check if name is defined
+	std::string name;
 	lua_getfield(L, table, "name");
 	if(lua_isstring(L, -1)){
-		std::string name = lua_tostring(L, -1);
+		name = lua_tostring(L, -1);
 		verbosestream<<"register_item_raw: "<<name<<std::endl;
 	} else {
 		throw LuaError(L, "register_item_raw: name is not defined or not a string");
@@ -3901,8 +3909,20 @@ static int l_register_item_raw(lua_State *L)
 
 	// Check if on_use is defined
 
-	// Read the item definition and register it
+	ItemDefinition def;
-	ItemDefinition def = read_item_definition(L, table);
+	// Set a distinctive default value to check if this is set
+	def.node_placement_prediction = "__default";
+
+	// Read the item definition
+	def = read_item_definition(L, table, def);
+
+	// Default to having client-side placement prediction for nodes
+	// ("" in item definition sets it off)
+	if(def.type == ITEM_NODE && def.node_placement_prediction == "__default"){
+		def.node_placement_prediction = name;
+	}
+	
+	// Register item definition
 	idef->registerItem(def);
 
 	// Read the node definition (content features) and register it

src/server.cpp

@@ -2971,8 +2971,16 @@ void Server::ProcessData(u8 *data, u32 datasize, u16 peer_id)
 					<<std::endl;
 			// Re-send block to revert change on client-side
 			RemoteClient *client = getClient(peer_id);
-			v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_under, BS));
+			// Digging completed -> under
-			client->SetBlockNotSent(blockpos);
+			if(action == 2){
+				v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_under, BS));
+				client->SetBlockNotSent(blockpos);
+			}
+			// Placement -> above
+			if(action == 3){
+				v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_above, BS));
+				client->SetBlockNotSent(blockpos);
+			}
 			return;
 		}
 
@@ -3104,7 +3112,14 @@ void Server::ProcessData(u8 *data, u32 datasize, u16 peer_id)
 				if(g_settings->getBool("creative_mode") == false)
 					playersao->setWieldedItem(item);
 			}
-
+			
+			// If item has node placement prediction, always send the above
+			// node to make sure the client knows what exactly happened
+			if(item.getDefinition(m_itemdef).node_placement_prediction != ""){
+				RemoteClient *client = getClient(peer_id);
+				v3s16 blockpos = getNodeBlockPos(floatToInt(pointed_pos_above, BS));
+				client->SetBlockNotSent(blockpos);
+			}
 		} // action == 3
 
 		/*