Implement mod for general purpose environmental physics effects

mods/ENTITIES/mcl_item_entity/init.lua

@@ -657,62 +657,6 @@ local function push_out_item_stuck_in_solid(self, dtime, p, def, is_in_water)
 	end
 end
 
-local function move_items_in_water (self, p, def, node, is_floating, is_in_water)
-	-- Move item around on flowing liquids; add 'source' check to allow items to continue flowing a bit in the source block of flowing water.
-	if def and not is_floating and (def.liquidtype == "flowing" or def.liquidtype == "source") then
-		self._flowing = true
-
-		--[[ Get flowing direction (function call from flowlib), if there's a liquid.
-        NOTE: According to Qwertymine, flowlib.quickflow is only reliable for liquids with a flowing distance of 7.
-        Luckily, this is exactly what we need if we only care about water, which has this flowing distance. ]]
-		local vec = flowlib.quick_flow(p, node)
-		-- Just to make sure we don't manipulate the speed for no reason
-		if vec.x ~= 0 or vec.y ~= 0 or vec.z ~= 0 then
-			-- Minecraft Wiki: Flowing speed is "about 1.39 meters per second"
-			local f = 1.2
-			-- Set new item moving speed into the direciton of the liquid
-			local newv = vector.multiply(vec, f)
-			-- Swap to acceleration instead of a static speed to better mimic MC mechanics.
-			self.object:set_acceleration(vector.new(newv.x, -0.22, newv.z))
-
-			self.physical_state = true
-			self._flowing = true
-			self.object:set_properties({
-				physical = true
-			})
-			return true
-		end
-		if is_in_water and def.liquidtype == "source" then
-			local cur_vec = self.object:get_velocity()
-			-- apply some acceleration in the opposite direction so it doesn't slide forever
-			local vec = {
-				x = 0 - cur_vec.x * 0.9,
-				y = 3 - cur_vec.y * 0.9,
-				z = 0 - cur_vec.z * 0.9
-			}
-			self.object:set_acceleration(vec)
-			-- slow down the item in water
-			local vel = self.object:get_velocity()
-			if vel.y < 0 then
-				vel.y = vel.y * 0.9
-			end
-			self.object:set_velocity(vel)
-			if self.physical_state ~= false or self._flowing ~= true then
-				self.physical_state = true
-				self._flowing = true
-				self.object:set_properties({
-					physical = true
-				})
-			end
-		end
-	elseif self._flowing == true and not is_in_water and not is_floating then
-		-- Disable flowing physics if not on/in flowing liquid
-		self._flowing = false
-		enable_physics(self.object, self, true)
-		return true
-	end
-end
-
 minetest.register_entity(":__builtin:item", {
 	initial_properties = {
 		hp_max = 1,
@@ -1053,7 +997,7 @@ minetest.register_entity(":__builtin:item", {
 
 		if push_out_item_stuck_in_solid(self, dtime, p, def, is_in_water) then return end
 
-		if move_items_in_water (self, p, def, node, is_floating, is_in_water) then return end
+		mcl_physics.apply_entity_environmental_physics(self)
 
 		-- If node is not registered or node is walkably solid and resting on nodebox
 		local nn = minetest.get_node(vector.offset(p, 0, -0.5, 0)).name

mods/ENTITIES/mcl_item_entity/mod.conf

@@ -1,4 +1,4 @@
 name = mcl_item_entity
 author = PilzAdam
 description = Dropped items will be attracted to the player like a magnet.
-depends = flowlib, mcl_enchanting
+depends = mcl_physics, mcl_enchanting

mods/ENTITIES/mcl_mobs/api.lua

@@ -411,7 +411,8 @@ local function on_step_work (self, dtime)
 	local player_in_active_range = self:player_in_active_range()
 	self:check_suspend(player_in_active_range)
 
-	self:check_water_flow()
+	-- Handle environmental physics
+	mcl_physics.apply_entity_environmental_physics(self)
 
 	if not self._jumping_cliff then
 		self._can_jump_cliff = self:can_jump_cliff()

mods/ENTITIES/mcl_mobs/mod.conf

@@ -2,4 +2,4 @@ name = mcl_mobs
 author = PilzAdam
 description = Adds a mob API for mods to add animals or monsters, etc.
 depends = mcl_particles, mcl_luck
-optional_depends = mcl_weather, mcl_explosions, mcl_hunger, mcl_worlds, invisibility, lucky_block, cmi, doc_identifier, mcl_armor, mcl_portals, mcl_experience, mcl_sculk
+optional_depends = mcl_weather, mcl_explosions, mcl_hunger, mcl_worlds, invisibility, lucky_block, cmi, doc_identifier, mcl_armor, mcl_portals, mcl_experience, mcl_sculk, mcl_physics

mods/ENTITIES/mcl_mobs/physics.lua

@@ -996,43 +996,7 @@ function mob_class:falling(pos)
 end
 
 function mob_class:check_water_flow()
-	-- Add water flowing for mobs from mcl_item_entity
+	-- Deprecated. Do nothing
-	local p, node, nn, def
-	p = self.object:get_pos()
-	node = minetest.get_node_or_nil(p)
-	if node then
-		nn = node.name
-		def = minetest.registered_nodes[nn]
-	end
-
-	-- Move item around on flowing liquids
-	if def and def.liquidtype == "flowing" then
-
-		--[[ Get flowing direction (function call from flowlib), if there's a liquid.
-		NOTE: According to Qwertymine, flowlib.quickflow is only reliable for liquids with a flowing distance of 7.
-		Luckily, this is exactly what we need if we only care about water, which has this flowing distance. ]]
-		local vec = flowlib.quick_flow(p, node)
-		-- Just to make sure we don't manipulate the speed for no reason
-		if vec.x ~= 0 or vec.y ~= 0 or vec.z ~= 0 then
-			-- Minecraft Wiki: Flowing speed is "about 1.39 meters per second"
-			local f = 1.39
-			-- Set new item moving speed into the direciton of the liquid
-			local newv = vector.multiply(vec, f)
-			self.object:set_acceleration({x = 0, y = 0, z = 0})
-			self.object:set_velocity({x = newv.x, y = -0.22, z = newv.z})
-
-			self.physical_state = true
-			self._flowing = true
-			self.object:set_properties({
-				physical = true
-			})
-			return
-		end
-	elseif self._flowing == true then
-		-- Disable flowing physics if not on/in flowing liquid
-		self._flowing = false
-		return
-	end
 end
 
 function mob_class:check_dying()

mods/ENVIRONMENT/mcl_physics/api.lua

@@ -0,0 +1,53 @@
+local mod = mcl_physics
+
+local registered_environment_effects = {}
+
+function mod.register_enviornment_effect(effect)
+	local list = registered_effects
+	list[#list + 1] = effect
+end
+
+function mod.get_environment_effect(pos, vel, staticdata, mass)
+	local v = vector.new(0,0,0)
+	local a = vector.new(0,0,0)
+
+	-- Accumulate all enviornmental effects
+	for _,effect in ipairs(registered_environment_effects) do
+		local dv,da = effect(pos, vel, staticdata)
+		if dv then
+			v = v + dv
+		end
+		if da then
+			a = a + da
+		end
+	end
+
+	if vector.length(v) > 0.01 or vector.length(a) > vector.length(a) > 0.01 then
+		return v,a
+	else
+		return -- nil,nil
+	end
+end
+
+function mod.apply_entity_environmental_physics(self, data)
+	data = data or {}
+
+	local pos = self.object:get_pos()
+	local vel = self.object:get_velocity()
+	local new_velocity,new_acceleration = mcl_physics.get_environment_effect(pos, vel, data, 1)
+
+	-- Update entity states
+	self._flowing = data.flowing
+
+	-- Apply environmental effects if there are any
+	if new_velocity or new_acceleration then
+		if new_acceleration then self.object:set_acceleration(new_acceleration) end
+		if new_velocity then self.object:set_velocity(new_velocity) end
+
+		self.physical_state = true
+		self._flowing = true
+		self.object:set_properties({
+			physical = true
+		})
+	end
+end

mods/ENVIRONMENT/mcl_physics/init.lua

@@ -0,0 +1,40 @@
+local modname = minetest.get_current_modname()
+local modpath = minetest.get_modpath(modname)
+local mod = {}
+mcl_physics = mod
+
+dofile(modpath.."/api.lua")
+
+-- TODO: move to Flowlib
+local FLOW_SPEED = 1.39
+mod.register_effect(function(pos, vel, staticdata)
+	-- Get the node and node definition
+	local node = minetest.get_node_or_nil(pos)
+	if not node then return end
+	local nodedef = minetest.registered_nodes[node.name]
+	if not nodedef then return end
+
+	-- Make sure we are in a liquid before continuing
+	local is_flowing = (nodedef.liquidtype == "flowing")
+	staticdata.flowing = is_flowing
+	if not is_flowing then
+		-- Apply decelleration if the entity moved from flowing water to 
+		-- stationary water
+		if nodedef.liquidtype == "source" then
+			return nil,vector.new(
+				0 - vel.x * 0.9,
+				3 - vel.y * 0.9,
+				0 - vel.z * 0.9
+			)
+		end
+		return
+	end
+
+	-- Get liquid flow direction
+	local vec = vector.multiply(flowlib.quick_flow(pos, node), FLOW_SPEED)
+	return vector.new(vec.x, -0.22, vec.z),nil
+end)
+
+-- Node effects
+mod.register_effect
+

mods/ENVIRONMENT/mcl_physics/mod.conf

@@ -0,0 +1,4 @@
+name = mcl_physics
+author = teknomunk
+description = Environmental physics
+depends = flowlib