-- Use the movement gravity for the downwards acceleration. -- The setting may change in-game but for simplicity we don't support this. local movement_gravity = tonumber(minetest.settings:get("movement_gravity")) or 9.81 -- get_flow_raw determines the horizontal flow vector for a flowing liquid node, -- or returns nothing if the flow is zero local neighbour_offsets = { {x=-1, y=0, z=0}, {x=1, y=0, z=0}, {x=0, y=0, z=-1}, {x=0, y=0, z=1} } local function get_flow_raw(pos) -- FIXME: Do we need to treat nodes with special liquid_range differently? local param2 = minetest.get_node(pos).param2 if param2 == 15 then -- The liquid has full height and flows downwards return end local flow = {x = 0, y = 0, z = 0} local height = param2 % 8 for n = 1, 4 do local node = minetest.get_node(vector.add(pos, neighbour_offsets[n])) local def = minetest.registered_nodes[node.name] local height_other if not def or def.walkable then -- A solid node, so no flow happens height_other = height elseif def.liquidtype == "source" then -- Assume that relevant liquid comes from this source height_other = 8 elseif def.liquidtype == "flowing" then -- This neighbour is also a flowing liquid height_other = node.param2 % 8 else -- There is a free space, e.g. air or a plant height_other = 0 end local fl = vector.multiply(neighbour_offsets[n], height - height_other) flow = vector.add(flow, fl) end if vector.equals(flow, {x = 0, y = 0, z = 0}) then return end return vector.normalize(flow) end -- get_flow caches the results from get_flow_raw for 10 s local flow_cache = {} setmetatable(flow_cache, {__mode = "kv"}) local function get_flow(pos) local vi = minetest.hash_node_position(pos) local t = minetest.get_us_time() if flow_cache[vi] and t - flow_cache[vi][1] < 10 * 1000000 then return flow_cache[vi][2] end local flow = get_flow_raw(pos) flow_cache[vi] = {t, flow} return flow end local item_entity = minetest.registered_entities["__builtin:item"] local old_on_step = item_entity.on_step item_entity.makes_footstep_sound = true -- The "bt_" prefix shows that the value comes from builtin_item item_entity.bt_timer = 0 item_entity.on_step = function(self, dtime, ...) -- Remember the velocity before an original on_step can change it local vel_desired if self.bt_reset_velocity then vel_desired = self.object:get_velocity() end old_on_step(self, dtime, ...) -- Ignore the item if it should not interact with physics if not self.physical_state then return end -- Reset the velocity if needed if vel_desired and not vector.equals(self.object:get_velocity(), vel_desired) then self.object:set_velocity(vel_desired) end -- For performance reasons, skip the remaining code in frequent steps self.bt_timer = self.bt_timer + dtime if self.bt_timer < 0.1 then return end self.bt_timer = 0 local p = self.object:get_pos() local pos = vector.round(p) local nodename = minetest.get_node(pos).name if self.bt_reset_velocity then -- Set the item acceleration to its default (changed again below) self.object:set_acceleration({x=0, y=-movement_gravity, z=0}) self.bt_reset_velocity = nil end local def = minetest.registered_nodes[nodename] if not def or not def.liquidtype or def.liquidtype ~= "flowing" then return end local flow = get_flow(pos) if not flow then return end local vel_current = vel_desired or self.object:get_velocity() local acc if vector.dot(vel_current, flow) < 1.0 then acc = vector.multiply(flow, 2.0) else -- The item is already accelerated by the fluids acc = {x = 0, y = 0, z = 0} end acc.y = -movement_gravity self.object:set_acceleration(acc) self.bt_reset_velocity = true end minetest.register_entity(":__builtin:item", item_entity)