Initial checkin.

This mostly already works - It's at the stage where I'm debugging
the tricky bits and most of the error and edge case handling, and
some of the lua tricks.

1 files changed, 457 insertions, 0 deletions

diff --git a/init.lua b/init.lua
new file mode 100644
index 0000000..e1c1892
--- /dev/null
+++ b/init.lua
@@ -0,0 +1,457 @@
+--
+-- Minetest Sedimentology Mod
+--
+local interval = 1.0
+local count = 20
+local radius = 100
+
+local stat_considered = 0
+local stat_displaced = 0
+local stat_degraded = 0
+
+local function round(f) 
+	if f >= 0 then
+		return math.floor(f + 0.5)
+	else
+		return math.ceil(f - 0.5)
+	end
+end
+
+local walker = {
+	[0] = {x = 0, z = 1},  {x = 1, z = 0},   {x = 0, z = -1}, {x = -1, z = 0},
+	{x = 1, z = 1},  {x = 1, z = -1},  {x = -1, z = 1}, {x = -1, z = -1},
+	{x = 2, z = 0},  {x = -2, z = 0},  {x = 0, z = 2},  {x = 0, z = -2},
+	{x = 2, z = 1},  {x = 2, z = -1},  {x = 1, z = 2},  {x = 1, z = -2},
+	{x = -1, z = 2}, {x = -1, z = -2}, {x = -2, z = 1}, {x = -2, z = -1},
+	{x = 2, z = 2},  {x = -2, z = 2},  {x = 2, z = -2}, {x = -2, z = -2}
+}
+local walker_step = 0
+local walker_start = 0
+local walker_phase = 4
+
+local function walker_f(x, y)
+	if x == 0 and y == 0 then
+		walker_step = 0
+	end
+
+	if walker_step == 0 or walker_step == 4 or walker_step == 8 or walker_step == 24 then
+		walker_start = math.floor(math.random() * 4.0)
+		walker_phase = 4
+	elseif walker_step == 12 then
+		walker_start = math.floor(math.random() * 8.0)
+		walker_phase = 8
+	end
+
+	local section_start = walker_step - (walker_step % walker_phase)
+	local section_part = ((walker_step - section_start) + walker_start) % walker_phase
+
+	walker_step = walker_step + 1
+	return walker[section_start + section_part]
+end
+
+local function roll(chance)
+	return (math.random() >= chance)
+end
+
+local function node_above(node)
+	local pos = minetest.get_pos(node)
+	return {x = pos.x, y = pos.y + 1, z = pos.z}
+end
+
+local function node_below(node)
+	local pos = minetest.get_pos(node)
+	return {x = pos.x, y = pos.y - 1, z = pos.z}
+end
+
+local function pos_is_node(pos)
+	return minetest.get_node_or_nil(pos)
+end
+
+local function node_is_air(node)
+	return node.name == "air"
+end
+
+local function node_is_plant(node)
+	if not node then
+		return false
+	end
+
+	local name = node.name
+	local drawtype = minetest.registered_nodes[name].drawtype
+	if drawtype == "plantlike" then
+		return true
+	end
+
+	if minetest.registered_nodes[node.name].groups.flora == 1 then
+		return true
+	end
+
+	return ((name == "default:leaves") or
+	        (name == "default:jungleleaves") or
+	        (name == "default:pine_needles") or
+	        (name == "default:cactus"))
+end
+
+local function node_is_water(node)
+	if not node then
+		return false
+	end
+
+	print(dump(node))
+
+	return ((node.name == "default:water_source") or
+	        (node.name == "default:water_flowing"))
+end
+
+local function node_is_lava(node)
+	if not node then
+		return false
+	end
+
+	return ((node.name == "default:lava_source") or
+	        (node.name == "default:lava_flowing"))
+end
+
+local function node_is_liquid(node)
+	if not node then
+		return false
+	end
+
+	local name = node.name
+	local drawtype = minetest.registered_nodes[name].drawtype
+	if drawtype then
+		if (drawtype == "liquid") or (drawtype == "flowingliquid") then
+			return true
+		end
+	end
+
+	return false
+end
+
+local function scan_for_water(pos, waterfactor)
+	local w = waterfactor
+	for xx = pos.x - 2,pos.x + 2,1 do
+		for yy = pos.y - 2,pos.y + 2,1 do
+			for zz = pos.z - 2,pos.z + 2,1 do
+				local nn = minetest.get_node({xx, yy, zz})
+				if nn.name == "default:water_flowing" then
+					return 0.25
+				elseif nn.name == "default:water_source" then
+					w = 0.125
+					break
+				end
+			end
+		end
+	end
+	return w
+end
+
+local function scan_for_vegetation(pos)
+	local v = 1.0
+	for xx = pos.x - 3,pos.x + 3,1 do
+		for yy = pos.y - 3,pos.y + 3,1 do
+			for zz = pos.z - 3,pos.z + 3,1 do
+				local nn = minetest.get_node({xx, yy, zz})
+				if node_is_plant(nn) then
+					-- factor distance to plant
+					local d = (math.abs(xx - pos.x) + math.abs(yy - pos.y) + math.abs(zz - pos.z)) / 3.0
+					-- scale it
+					local vv = 0.5 / (4.0 - d)
+					-- only take the lowest value
+					if (vv < v) then
+						v = vv
+					end
+				end
+			end
+		end
+	end
+	return v
+end
+
+local function node_is_valid_target_for_displacement(pos)
+	local node = minetest.get_node(pos)
+
+	if node_is_liquid(node) then
+		return true
+	elseif node_is_air(node) then
+		return true
+	elseif node_is_plant(node) then
+		return true
+	end
+	return false
+end
+
+local function node_is_locked_in(pos)
+	if
+		node_is_valid_target_for_displacement({x = pos.x - 1, y = pos.y, z = pos.z}) or
+		node_is_valid_target_for_displacement({x = pos.x + 1, y = pos.y, z = pos.z}) or
+		node_is_valid_target_for_displacement({x = pos.x, y = pos.y, z = pos.z - 1}) or
+		node_is_valid_target_for_displacement({x = pos.x, y = pos.y, z = pos.z + 1})
+	then
+		return false
+	end
+	return true
+end
+
+local function find_deposit_location(x, y, z)
+	local yy = y
+	while true do
+		if node_is_valid_target_for_displacement({x = x, y = yy, z = z}) then
+			yy = yy - 1
+			if yy < -32768 then
+				return y
+			end
+		else
+			return yy + 1
+		end
+	end
+end
+
+local function sed()
+	local underliquid = 0
+
+	-- pick a random block in (radius) around (random online player)
+	local playerlist = minetest.get_connected_players()
+	local playercount = table.getn(playerlist)
+	if playercount == 0 then
+		return
+	end
+	local r = math.random(playercount)
+	local randomplayer = playerlist[r]
+	local playerpos = randomplayer:getpos()
+	local pos = {
+		x = math.random(playerpos.x - radius, playerpos.x + radius),
+		y = 0,
+		z = math.random(playerpos.z - radius, playerpos.z + radius)
+	}
+	local node = minetest.get_pos(pos)
+
+	stat_considered = stat_considered + 1
+
+	-- now go find the topmost non-air block
+	repeat
+		node = node_above(node)
+	until node_is_air(node)
+
+	repeat
+		node = node_below(node)
+	until not node_is_air(node)
+
+	-- then search under water/lava and any see-through plant stuff
+	while (node_is_liquid(node)) do
+		underliquid = underliquid + 1
+		node = node_below(node)
+	end
+
+	-- check if we're material that we can do something with
+	local hardness = 1.0
+	local resistance = 1.0
+
+	if      node.name == "default:dirt" or
+		node.name == "default:dirt_with_grass" or
+		node.name == "default:dirt_with_grass_footsteps" or
+		node.name == "default:dirt_with_snow" then
+		-- default hardness (very soft) here
+	elseif node.name == "default:sand" or node.name == "default:desert_sand" then
+		-- sand is "hard" to break into clay, but moves easily
+		hardness = 0.01
+	elseif node.name == "default:gravel" then
+		hardness = 0.15
+		resistance = 0.70
+	elseif node.name == "default:clay" then
+		resistance = 0.3
+	elseif node.name == "default:sandstone" or
+		node.name == "default:cobble" or
+		node.name == "default:mossycobble" or
+		node.name == "default:desert_cobble" then
+		hardness = 0.05
+		resistance = 0.05
+	elseif node.name == "default:desert_stone" or
+		node.name == "default:stone" then
+		hardness = 0.01
+		resistance = 0.01
+	elseif node.name == "default:stone_with_coal" or
+		node.name == "default:stone_with_iron" or
+		node.name == "default:stone_with_copper" or
+		node.name == "default:stone_with_gold" or
+		node.name == "default:stone_with_mese" or
+		node.name == "default:stone_with_diamond" then
+		hardness = 0.0001
+		resistance = 0.01
+	else
+		-- we don't do anything with this node type
+		return
+	end
+
+	-- determine nearby water scaling
+	local waterfactor = 0.01
+	if underliquid > 0 then
+		waterfactor = 0.5
+	else
+		waterfactor = scan_for_water(pos, waterfactor)
+	end
+
+	if roll(waterfactor) then
+		return
+	end
+
+	-- slow down deeper under sea level (wave action reduced energy)
+	if underliquid and pos.y < 0.0 then
+		if roll(2.0 * math.pow(0.5, 0.0 - pos.y)) then
+			return
+		end
+	end
+
+	-- factor in vegetation that slows erosion down
+	if roll(scan_for_vegetation(pos)) then
+		return
+	end
+
+
+	-- displacement - before we erode this material, we check to see if
+	-- it's not easier to move the material first. If that fails, we'll
+	-- end up degrading the material as calculated
+
+	if not node_is_locked_in(pos) then
+		local steps = 8
+
+		if node.name == "default:sand" or
+		   node.name == "default:desert_sand" or
+		   (underliquid > 0) then
+			steps = 24
+		else
+			steps = 8
+		end
+
+		-- walker algorithm here
+		local lowest = pos.y
+		local lowesto = {x = pos.x, z = pos.z}
+		local o = {x = 0, z = 0}
+
+		for step = 1, steps, 1 do
+			o = walker_f(o.x, o.z)
+			local h = find_deposit_location(pos.x + o.x, lowest, pos.z + o.z)
+print("walking step " .. step .. " to " .. pos.x + o.x .. ", " .. pos.z + o.z .. " -> lowest = " .. h)
+
+			if h < lowest then
+				lowest = h
+				lowesto = o
+			end
+		end
+
+		if lowest < pos.y then
+			local tpos = {x = pos.x + o.x, y = lowest, z = pos.z + o.z}
+
+			if not roll(resistance) then
+				local tnode = minetest.get_node(tpos)
+
+				if node_is_air(tnode) or node_is_plant(tnode) or node_is_liquid(tnode) then
+					-- time to displace the node from pos to tpos
+					minetest.place_node(tpos, node)
+					minetest.get_meta(tpos):from_table(minetest.get_meta(pos):to_table())
+					minetest.remove_node(pos)
+
+					-- FIXME
+					-- fix water at source location
+					-- fix water at target location
+
+					print("Moved:", node.name, pos.x, pos.y, pos.z, "to:", tnode.name, tpos.x, tpos.y, tpos.z)
+					stat_displaced = stat_displaced + 1
+
+					-- done - don't degrade this block further
+					return
+				else
+					--debug
+					print("displacement failed: target has something:", tpos.x, tpos.y, tpos.z)
+				end
+			end
+		end
+	end
+
+	-- degrade
+
+	-- compensate speed for grass/dirt cycle
+
+	-- sand only becomes clay under sealevel
+	if ((node.name == "default:sand" or node.name == "default:desert_sand") and (underliquid > 0) and pos.y >= 0.0) then
+		return
+	end
+
+	-- prevent dirt-to-sand outside deserts
+	-- FIXME should account for Biome here too
+	if (underliquid < 1) and (node.name == "default:sand" or node.name == "default:desert_sand") then
+		return
+	end
+
+	if roll(hardness) then
+		return
+	end
+
+	-- finally, determine new material type
+	local newmat = "air"
+
+	if node.name == "default:dirt" then
+		newmat = "default:sand"
+	elseif node.name == "default:dirt_with_grass" or
+	       node.name == "default:dirt_with_grass_footsteps" or
+	       node.name == "default:dirt_with_snow" then
+		newmat = "default:dirt"
+	elseif node.name == "default:sand" or node.name == "default:desert_sand" then
+		newmat = "default:clay"
+	elseif node.name == "default:gravel" then
+		newmat = "default:dirt"
+	elseif node.name == "default:clay" then
+		return
+	elseif node.name == "default:sandstone" or
+	       node.name == "default:cobble" or
+	       node.name == "default:mossycobble" or
+	       node.name == "default:desert_cobble" then
+		newmat = "default:gravel"
+	elseif node.name == "default:desert_stone" or
+	       node.name == "default:stone" then
+		newmat = "default:cobble"
+	elseif node.name == "default:stone_with_coal" or
+	       node.name == "default:stone_with_iron" or
+	       node.name == "default:stone_with_copper" or
+	       node.name == "default:stone_with_gold" or
+	       node.name == "default:stone_with_mese" or
+	       node.name == "default:stone_with_diamond" then
+		newmat = "default:stone"
+	else
+		print("wut", node.name)
+		return
+	end
+
+	minetest.set_node(pos, {name = newmat})
+
+	stat_degraded = stat_degraded + 1
+end
+
+local function sedimentology()
+	-- select a random point that is loaded in the game
+	for c=1,count,1 do
+		sed()
+	end
+	-- requeue a timer to call again
+	minetest.after(interval, sedimentology)
+end
+
+local function sedcmd(name, param)
+	if param == "stats" then
+		local output = "Sedimentology mod statistics:" ..
+			"\nconsidered: " .. stat_considered ..
+			"\ndisplaced: " .. stat_displaced ..
+			"\ndegraded: " .. stat_degraded
+		return true, output
+	end
+	return true, "Command completed succesfully"
+end
+
+minetest.register_chatcommand("sed", {
+	params = "stats|...",
+	description = "Various action commands for the sedimentology mod",
+	func = sedcmd
+})
+
+minetest.after(interval, sedimentology)
+print("Initialized Sedimentology")