A modification of the builtin items in Minetest
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-- 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)