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Farming: Convert plants to use node timers

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This PR requires @minetest/minetest#3677

Farming and plant growth has traditionally in minetest been
implemented using ABM's. These ABM's periodically tick and cause
plants to grow. The way these ABM's work has several side effects
that can be considered harmful.

Not to mention a comprehensive list of downsides here, but ABM's
are chance-dependent. That results in the chance that some nodes
potentially never get processed by the ABM action, and others get
processed always. One can easily find this effect by planting a large
field of crops, and seeing that some nodes are fully grown really
fast, and some just won't make it to fully grown status even after
hours or play time.

One could solve the problem by making the ABM's slower, and giving them
a 100% of action, but this would cause the entire field to grow a step
instantly at ABM intervals, and is both ugly, and a large number of
node updates that needs to be sent out to each client. Very un-ideal.

With NodeTimers though, each node will see a separate node timer event,
and they will likely not coalesce. This means that we can stop relying
on chance to distribute plant growth, and assign a single timer event
to grow the plant to the next phase.  Due to the timer implementation,
we won't ever miss a growth event, and we can re-scehdule them until
the plant has reached full size.

Previously, plants would attempt to grow every 9 seconds, with a
chance of 1/20. This means typically, a plant would need 9*20 seconds
to grow 1 phase, and since there are 8 steps, a typical plant growth
would require 9*20*8 ABM node events. (spread out over 9*8 ABM actual
underlying events per block, roughly).

because plants are likely not growing to full for a very long time
due to statistics working against it (5% of the crops take 20x longer
than the median to grow to full, we'd be seeing ABMs fire possibly
up to 9*20*8*20 with a 95% confidence interval (the actual math
is likely off, but the scale should be correct). That's incredibly
wasteful. We'd reach those conditions easily with 20 plant nodes.

Now, after we convert to NodeTimers, each plant node will see exactly
8 NodeTimer events, and no more. This scales lineairly per plant.

I've tuned the growth rate of crops to be mature in just under 3
whole days. That's about 1hr of game time. Previously, about half
the crops would grow to full in under 2 days, but many plants would
still not be mature by the end of day 3. This is more consistent.

An additional problem in the farming mod was that the final fully-grown
plant was also included in the ABM, causing infinite more ABM's even
after the entire field had grown to completion.

Now, we're left with the problem that none of the pre-existing plants
have actual node timers started on them, and we do not want a new ABM
to fix this issue, since that would be wasteful.  Fortunately, there
is now an LBM concept, and we can use it to assure that NodeTimers
on crop nodes are properly started, and only have to do the actual
conversion once per block, ever.

We want to provide a fairly similar growth rate after this conversion
and as such I've resorted to modelling some statistical data. For this
I created a virtual 32x32 crop field with 9 steps (8 transitions)
as is the default wheat crop. We then apply a step where 1 in 20
plants in the field grows a step (randomly chosen) and count the
number of steps needed to get to 25%, 50, 75% and 95% grown.

The resulting data looks as follows:

25% - ~120 steps * 9 sec / abm = 1080s
50% - ~152 steps               = 1368s
75% - ~194 steps               = 1746s
95% - ~255 steps               = 2295s

Next, we want to create a model where the chance that a crop grows
is 100% every node timer. Since there will only be 8 steps ever,
we want the slowest crops to grow in intervals of ~ 2300 / 8 seconds
and the fastest 1/4 of crops to grow 1080 / 8 seconds intervals.
We can roughly compare this to a normal distribution with a median
of 1400 with a stddev of ~350 (thick fingering this one here).

The rest is a bit of thick-fingering to get similar growth rates,
taking into account that ABM's fire regularly so if they're missed
it's fairly painless, but our timers are going to be 1-2 minutes
apart at minimum. I calculate the timer should be around 150s
median, and experimented with several jitter ranges.

Eventually I settled for now on [80,200] with a redo of [40,80],
meaning that each growth step at minimum takes (80 to 200) seconds,
and if a negative growth condition was found (darkness, soil not
wet, etc), then the growth step is retried every (40 to 80) seconds.

The end result is a growth period from seed to full in ~ 2.25
minetest days. This is a little bit shorter than the current
growth rate but the chances you'll miss timer ticks is a bit
larger, so in normal gameplay it should be fairly comparable.

A side effect is that fields grow to full yield fairly quickly
after crops make it to mature growth, and no crops are mature
a very long time before the majority grows to full. The spread
and view over a growing field is also fairly even, there's no
large updates with plenty of nodes. Just a node here or there
every second or so in large fields.

Ultimately, we get rid of ABM rollercoasters that cause tens of
node updates every 9 seconds. This will help multiplayer servers
likely a lot.
This commit is contained in:
Auke Kok 2016-02-22 22:28:17 -08:00 committed by paramat
parent fc902a77de
commit 70ef7864c1
1 changed files with 105 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

172
mods/farming/api.lua
View File

@ -1,3 +1,4 @@
-- Wear out hoes, place soil
-- TODO Ignore group:flower
farming.hoe_on_use = function(itemstack, user, pointed_thing, uses)
@ -9,11 +10,11 @@ farming.hoe_on_use = function(itemstack, user, pointed_thing, uses)
if pt.type ~= "node" then
return
end
local under = minetest.get_node(pt.under)
local p = {x=pt.under.x, y=pt.under.y+1, z=pt.under.z}
local above = minetest.get_node(p)
-- return if any of the nodes is not registered
if not minetest.registered_nodes[under.name] then
return
@ -21,23 +22,23 @@ farming.hoe_on_use = function(itemstack, user, pointed_thing, uses)
if not minetest.registered_nodes[above.name] then
return
end
-- check if the node above the pointed thing is air
if above.name ~= "air" then
return
end
-- check if pointing at soil
if minetest.get_item_group(under.name, "soil") ~= 1 then
return
end
-- check if (wet) soil defined
local regN = minetest.registered_nodes
if regN[under.name].soil == nil or regN[under.name].soil.wet == nil or regN[under.name].soil.dry == nil then
return
end
if minetest.is_protected(pt.under, user:get_player_name()) then
minetest.record_protection_violation(pt.under, user:get_player_name())
return
@ -47,14 +48,13 @@ farming.hoe_on_use = function(itemstack, user, pointed_thing, uses)
return
end
-- turn the node into soil, wear out item and play sound
minetest.set_node(pt.under, {name = regN[under.name].soil.dry})
minetest.sound_play("default_dig_crumbly", {
pos = pt.under,
gain = 0.5,
})
if not minetest.setting_getbool("creative_mode") then
itemstack:add_wear(65535/(uses-1))
end
@ -119,6 +119,15 @@ farming.register_hoe = function(name, def)
end
end
-- how often node timers for plants will tick, +/- some random value
local function tick(pos)
minetest.get_node_timer(pos):start(math.random(166, 286))
end
-- how often a growth failure tick is retried (e.g. too dark)
local function tick_again(pos)
minetest.get_node_timer(pos):start(math.random(40, 80))
end
-- Seed placement
farming.place_seed = function(itemstack, placer, pointed_thing, plantname)
local pt = pointed_thing
@ -129,10 +138,10 @@ farming.place_seed = function(itemstack, placer, pointed_thing, plantname)
if pt.type ~= "node" then
return
end
local under = minetest.get_node(pt.under)
local above = minetest.get_node(pt.above)
if minetest.is_protected(pt.under, placer:get_player_name()) then
minetest.record_protection_violation(pt.under, placer:get_player_name())
return
@ -142,7 +151,6 @@ farming.place_seed = function(itemstack, placer, pointed_thing, plantname)
return
end
-- return if any of the nodes is not registered
if not minetest.registered_nodes[under.name] then
return
@ -150,30 +158,86 @@ farming.place_seed = function(itemstack, placer, pointed_thing, plantname)
if not minetest.registered_nodes[above.name] then
return
end
-- check if pointing at the top of the node
if pt.above.y ~= pt.under.y+1 then
return
end
-- check if you can replace the node above the pointed node
if not minetest.registered_nodes[above.name].buildable_to then
return
end
-- check if pointing at soil
if minetest.get_item_group(under.name, "soil") < 2 then
return
end
-- add the node and remove 1 item from the itemstack
minetest.add_node(pt.above, {name = plantname, param2 = 1})
tick(pt.above)
if not minetest.setting_getbool("creative_mode") then
itemstack:take_item()
end
return itemstack
end
farming.grow_plant = function(pos, elapsed)
local node = minetest.get_node(pos)
local name = node.name
local def = minetest.registered_nodes[name]
if not def.next_plant then
-- disable timer for fully grown plant
return
end
-- grow seed
if minetest.get_item_group(node.name, "seed") and def.fertility then
local soil_node = minetest.get_node_or_nil({x = pos.x, y = pos.y - 1, z = pos.z})
if not soil_node then
tick_again(pos)
return
end
-- omitted is a check for light, we assume seeds can germinate in the dark.
for _, v in pairs(def.fertility) do
if minetest.get_item_group(soil_node.name, v) ~= 0 then
minetest.swap_node(pos, {name = def.next_plant})
if minetest.registered_nodes[def.next_plant].next_plant then
tick(pos)
return
end
end
end
return
end
-- check if on wet soil
local below = minetest.get_node({x = pos.x, y = pos.y - 1, z = pos.z})
if minetest.get_item_group(below.name, "soil") < 3 then
tick_again(pos)
return
end
-- check light
local light = minetest.get_node_light(pos)
if not light or light < def.minlight or light > def.maxlight then
tick_again(pos)
return
end
-- grow
minetest.swap_node(pos, {name = def.next_plant})
-- new timer needed?
if minetest.registered_nodes[def.next_plant].next_plant then
tick(pos)
end
return
end
-- Register plants
farming.register_plant = function(name, def)
local mname = name:split(":")[1]
@ -200,6 +264,7 @@ farming.register_plant = function(name, def)
end
-- Register seed
local lbm_nodes = {mname .. ":seed_" .. pname}
local g = {seed = 1, snappy = 3, attached_node = 1}
for k, v in pairs(def.fertility) do
g[v] = 1
@ -228,6 +293,10 @@ farming.register_plant = function(name, def)
on_place = function(itemstack, placer, pointed_thing)
return farming.place_seed(itemstack, placer, pointed_thing, mname .. ":seed_" .. pname)
end,
next_plant = mname .. ":" .. pname .. "_1",
on_timer = farming.grow_plant,
minlight = def.minlight,
maxlight = def.maxlight,
})
-- Register harvest
@ -237,7 +306,7 @@ farming.register_plant = function(name, def)
})
-- Register growing steps
for i=1,def.steps do
for i = 1, def.steps do
local drop = {
items = {
{items = {mname .. ":" .. pname}, rarity = 9 - i},
@ -248,6 +317,16 @@ farming.register_plant = function(name, def)
}
local nodegroups = {snappy = 3, flammable = 2, plant = 1, not_in_creative_inventory = 1, attached_node = 1}
nodegroups[pname] = i
local next_plant = nil
local on_timer = nil
if i < def.steps then
next_plant = mname .. ":" .. pname .. "_" .. (i + 1)
on_timer = farming.grow_plant
lbm_nodes[#lbm_nodes + 1] = mname .. ":" .. pname .. "_" .. i
end
minetest.register_node(mname .. ":" .. pname .. "_" .. i, {
drawtype = "plantlike",
waving = 1,
@ -262,61 +341,20 @@ farming.register_plant = function(name, def)
},
groups = nodegroups,
sounds = default.node_sound_leaves_defaults(),
next_plant = next_plant,
on_timer = farming.grow_plant,
minlight = def.minlight,
maxlight = def.maxlight,
})
end
-- Growing ABM
minetest.register_abm({
nodenames = {"group:" .. pname, "group:seed"},
neighbors = {"group:soil"},
interval = 9,
chance = 20,
-- replacement LBM for pre-nodetimer plants
minetest.register_lbm({
name = "farming:start_nodetimer_" .. mname .. "_" .. pname,
nodenames = lbm_nodes,
action = function(pos, node)
local plant_height = minetest.get_item_group(node.name, pname)
-- return if already full grown
if plant_height == def.steps then
return
end
local node_def = minetest.registered_items[node.name] or nil
-- grow seed
if minetest.get_item_group(node.name, "seed") and node_def.fertility then
local can_grow = false
local soil_node = minetest.get_node_or_nil({x = pos.x, y = pos.y - 1, z = pos.z})
if not soil_node then
return
end
for _, v in pairs(node_def.fertility) do
if minetest.get_item_group(soil_node.name, v) ~= 0 then
can_grow = true
end
end
if can_grow then
minetest.set_node(pos, {name = node.name:gsub("seed_", "") .. "_1"})
end
return
end
-- check if on wet soil
pos.y = pos.y - 1
local n = minetest.get_node(pos)
if minetest.get_item_group(n.name, "soil") < 3 then
return
end
pos.y = pos.y + 1
-- check light
local ll = minetest.get_node_light(pos)
if not ll or ll < def.minlight or ll > def.maxlight then
return
end
-- grow
minetest.set_node(pos, {name = mname .. ":" .. pname .. "_" .. plant_height + 1})
end
tick_again(pos)
end,
})
-- Return