Mobs: Add fall damage

mods/rp_mobs/API.md

@@ -36,7 +36,6 @@ You can use the following template:
 		drops = { ADD_YOUR_DROPS_HERE },
 		decider = function(self) --[[ do things ]] end,
 		entity_definition = {
-			-- Add 
 			on_activate = function(self)
 				rp_mobs.init_physics(self)
 				rp_mobs.init_tasks(self)
@@ -110,6 +109,15 @@ functions to learn more about how the node damage mechanic works.
 Node damage can be temporarily disabled during the mob’s lifetime by setting the
 entity field `_get_node_damage` to false.
 
+### Fall damage
+
+Fall damage hurts the mob when it hits the ground too hard.
+The fall damage calculation works differently than for players (see
+`rp_mobs.handle_fall_damage` for details.
+
+To enable fall damage , add `rp_mobs.init_fall_damage` in `on_activate` and
+`rp_mobs.handle_fall_damage` in `on_step`.
+
 ### Breath / drowning
 
 Drowning makes mobs take drowning damage when inside a particular node.
@@ -124,7 +132,7 @@ by manipulating the drowning fields (see the mob field reference).
 ### Breeding
 
 Breeding will make mobs mate and create offspring. To enable, add
-`rp_mobs.handle_breeding` in `on_step`. 
+`rp_mobs.handle_breeding` in `on_step`.
 
 In particular, to breed, two adult mobs of the same type need to be “horny” and close
 to each other. Then, a random mob of the pair gets pregnant and will soon
@@ -137,6 +145,7 @@ There are two ways to make a mob horny:
 
 Only adults should be horny.
 
+
 ## Mob field reference
 
 Mob entities use a bunch of custom fields. You may read and edit them at runtime.
@@ -155,6 +164,7 @@ These fields are available:
 ### Damage
 
 * `_get_node_damage`: `true` when mob can take damage from nodes (`damage_per_second`) (default: false)
+* `_get_fall_damage`: `true` when mob can take fall damage (default: false)
 * `_can_drown`: `true` when mob has breath and can drown in nodes with `drowning` attribute (default: false)
 * `_drowning_point`: See `rp_mobs.init_breath`.
 * `_breath_max`: Maximum breath (ignored if `_can_drown` isn’t true)
@@ -306,6 +316,21 @@ Parameters:
 * `self`: The mob
 * `get_node_damage`: If `true`, mob will receive damage from nodes
 
+### `rp_mobs.init_fall_damage(self, get_fall_damage)`
+
+Initializes the fall damage for the given mob,
+If you want the mob to have this, put this into `on_activate`.
+
+If this is the first time the function is called, the
+associated entity fields will be initialized. On subsequent
+calls, this function does nothing because the fields are already
+initialized.
+
+Parameters:
+
+* `self`: The mob
+* `get_fall_damage`: If `true`, mob will receive fall damage
+
 ### `rp_mobs.attempt_capture = function(mob, capturer, capture_chances, force_take, replace_with)`
 
 Attempt to capture mob by capturer (a player). This requires a mob to have a mob available as
@@ -355,6 +380,25 @@ Otherwise, no damage will be taken.
 Must be called in the `on_step` function in every step.
 `dtime` is the `dtime` argument of `on_step`.
 
+### `rp_mobs.handle_fall_damage(mob, dtime, moveresult)`
+
+Handles fall damage for the mob if the entity field
+`_get_fall_damage` is `true`.
+
+Fall damage is calculated differently than for
+players and there is no guarante the calculation
+algorithm will be forwards-compatible. It increases
+linearly with the fall height. Fall damage is further-
+more modified by the `add_fall_damage_percent` group
+if falling on a node. Adding the armor group
+`add_fall_damage_percent` will also modify the
+fall damage the mob will receive (like for players,
+see `lua_api.md`).
+
+This function must be called in the `on_step` function
+in every step. `dtime` and `moveresult` are the same as
+in `on_step`.
+
 ### `rp_mobs.handle_drowning(mob, dtime)`
 
 Handles breath and drowning damage for the mob
@@ -387,10 +431,18 @@ mob’s yaw.
 Must be called in the `on_step` function in every step.
 `dtime` is the `dtime` argument of `on_step`.
 
-### `rp_mobs.handle_environment_damage(mob, dtime)`
+### `rp_mobs.handle_environment_damage(mob, dtime, moveresult)`
 
 Handle all environment damages. This is is the same as
-calling `rp_mobs.handle_node_damage` and `rp_mobs.handle_drowning`.
+calling:
+
+* `rp_mobs.handle_fall_damage`
+* `rp_mobs.handle_node_damage`
+* `rp_mobs.handle_drowning`
+
+Must be called in `on_step` every step.
+`mob` is the mob. The `dtime` and `moveresult`
+arguments are the same as for `on_step`.
 
 ### `rp_mobs.on_death_default(mob, killer)`
 

mods/rp_mobs/api.lua

@@ -13,6 +13,8 @@ local NODE_DAMAGE_TIME = 1.0
 local DROWNING_TIME = 2.0
 -- Interval (seconds) at which mobs regenerate breath (if they have breath)
 local REBREATH_TIME = 0.5
+-- Minimum Y fall height before starting to take fall damage
+local FALL_DAMAGE_HEIGHT = 5
 
 -- List of entity variables to store in staticdata
 -- (so they are persisted when unloading)
@@ -395,15 +397,24 @@ function rp_mobs.init_breath(self, can_drown, def)
 		return
 	end
 	self._can_drown = can_drown
-	self._breath_max = breath_max
-	self._breath = breath_max
+	self._breath_max = def.breath_max
+	self._breath = def.breath_max
 	self._drowning_point = def.drowning_point
 end
 function rp_mobs.init_node_damage(self, get_node_damage)
 	if self._get_node_damage ~= nil then
 		return
 	end
-	self._get_node_damage = get_node_damagee
+	self._get_node_damage = get_node_damage
+end
+function rp_mobs.init_fall_damage(self, get_fall_damage)
+	if self._get_fall_damage ~= nil then
+		return
+	end
+	self._get_fall_damage = get_fall_damage
+	if not self._standing_y then
+		self._standing_y = self.object:get_pos().y
+	end
 end
 
 function rp_mobs.handle_node_damage(self, dtime)
@@ -501,14 +512,84 @@ function rp_mobs.handle_drowning(self, dtime)
 	end
 end
 
-function rp_mobs.handle_environment_damage(self, dtime)
+function rp_mobs.handle_fall_damage(self, dtime, moveresult)
+	if not self._get_fall_damage then
+		return
+	end
+	if not rp_mobs.is_alive(self) then
+		return
+	end
+
+	local mob_fall_factor = 1
+	local armor = self.object:get_armor_groups()
+	-- Apply mob’s fall_damage_add_percent modifier
+	if armor.fall_damage_add_percent then
+		mob_fall_factor = 1 + armor.fall_damage_add_percent/100
+	end
+	local is_immortal = armor.immortal ~= nil and armor.immortal ~= 0
+	if moveresult.collides then
+		local collisions = moveresult.collisions
+		for c=1, #collisions do
+			local collision = collisions[c]
+			local old_v = collision.old_velocity
+			local new_v = collision.new_velocity
+			local speed_diff = vector.subtract(new_v, old_v)
+
+			-- We only care about floor collision
+			if (not (speed_diff.y < 0 or old_v.y >= 0)) then
+
+				-- Apply node’s fall_damage_add_percent modifier
+				local node_fall_factor = 1.0
+				if collision.type == "node" then
+					local node = minetest.get_node(collision.node_pos)
+					local g = minetest.get_item_group(node.name, "fall_damage_add_percent")
+					if g ~= 0 then
+						node_fall_factor = 1 + g/100
+					end
+				end
+
+				-- Calculate final fall damage modifier
+				local pre_factor = mob_fall_factor * node_fall_factor
+
+				-- Fall damage is based on fall height. When falling at least the
+				-- FALL_DAMAGE_HEIGHT, mob may take 1 damage per extra node fallen
+				local y_diff = self._standing_y - self.object:get_pos().y
+
+				-- Apply damage modifier
+				y_diff = y_diff * pre_factor
+
+				if (y_diff >= FALL_DAMAGE_HEIGHT and (not is_immortal) and pre_factor > 0) then
+					local damage_f = y_diff - FALL_DAMAGE_HEIGHT
+					local damage = math.floor(math.min(damage_f + 0.5, 65535))
+					if damage > 0 then
+						local hp = self.object:get_hp() - damage
+						self.object:set_hp(hp, { type = "fall" })
+						if hp <= 0 then
+							self._dying = true
+							return
+						end
+					end
+				end
+			end
+		end
+	end
+	if moveresult.touching_ground then
+		self._standing_y = self.object:get_pos().y
+	end
+end
+
+function rp_mobs.handle_environment_damage(self, dtime, moveresult)
+	rp_mobs.handle_fall_damage(self, dtime, moveresult)
 	rp_mobs.handle_node_damage(self, dtime)
 	rp_mobs.handle_drowning(self, dtime)
 end
 
+
 -- Entity variables to persist:
 rp_mobs.add_persisted_entity_vars({
 	"_get_node_damage",	-- true when mob can take damage from nodes (damage_per_second)
+	"_get_fall_damage",	-- true when mob can take fall damage
+	"_standing_y",		-- Y coordinate when mob was standing on ground. Internally used for fall damage calculations
 	"_can_drown",		-- true when mob has breath and can drown in nodes with `drowning` attribute
 	"_drowning_point",	-- The position offset that will be checked when doing the drowning check
 	"_breath_max",		-- Maximum breath

mods/rp_mobs_mobs/boar.lua

@@ -38,6 +38,7 @@ rp_mobs.register_mob("rp_mobs_mobs:boar", {
 		textures = { "mobs_boar.png" },
 		makes_footstep_sound = true,
 		on_activate = function(self)
+			rp_mobs.init_fall_damage(self, true)
 			rp_mobs.init_breath(self, true, {
 				breath_max = 10,
 				drowning_point = vector.new(0, -0.1, 0.49)
@@ -48,8 +49,8 @@ rp_mobs.register_mob("rp_mobs_mobs:boar", {
 			rp_mobs.activate_gravity(self)
 			rp_mobs.init_tasks(self)
 		end,
-		on_step = function(self, dtime)
-			rp_mobs.handle_environment_damage(self, dtime)
+		on_step = function(self, dtime, moveresult)
+			rp_mobs.handle_environment_damage(self, dtime, moveresult)
 			rp_mobs.handle_physics(self)
 			rp_mobs.handle_tasks(self, dtime)
 			rp_mobs.handle_breeding(self, dtime)

mods/rp_mobs_mobs/dummy.lua

@@ -7,17 +7,9 @@ local dummy_texture = "mobs_dummy.png"
 rp_mobs.register_mob("rp_mobs_mobs:dummy", {
 	description = S("Dummy"),
 	decider = function(self)
-		local task = rp_mobs.create_task({label="Dummy stuff"})
-		rp_mobs.add_microtask_to_task(self, rp_mobs.microtasks.set_yaw("random"), task)
-		local yaw = (math.random(0, 10000) / 10000) * (math.pi*2)
-		rp_mobs.add_microtask_to_task(self, rp_mobs.microtasks.walk_straight_towards(1, "pos", vector.zero(), 0.2), task)
-		local sleep_time = math.random(500, 2000)/1000
-		local mt_sleep = rp_mobs.microtasks.sleep(sleep_time)
-		rp_mobs.add_microtask_to_task(self, mt_sleep, task)
-		rp_mobs.add_task(self, task)
 	end,
 	entity_definition = {
-		hp_max = 1,
+		hp_max = 20,
 		physical = true,
 		collisionbox = {-0.5, -0.5, -0.5, 0.5, 0.5, 0.5},
 		selectionbox = {-0.5, -0.5, -0.5, 0.5, 0.5, 0.5, rotate=true},
@@ -25,10 +17,14 @@ rp_mobs.register_mob("rp_mobs_mobs:dummy", {
 		textures = { dummy_texture, dummy_texture, dummy_texture, dummy_texture, dummy_texture, dummy_texture },
 		makes_footstep_sound = false,
 		on_activate = function(self)
+			rp_mobs.init_fall_damage(self, true)
 			rp_mobs.init_physics(self)
 			rp_mobs.init_tasks(self)
+			rp_mobs.activate_gravity(self)
+			self._get_fall_damage = true
 		end,
-		on_step = function(self, dtime)
+		on_step = function(self, dtime, moveresult)
+			rp_mobs.handle_environment_damage(self, dtime, moveresult)
 			rp_mobs.handle_physics(self)
 			rp_mobs.handle_tasks(self, dtime)
 			rp_mobs.decide(self)

mods/rp_mobs_mobs/sheep.lua

@@ -80,6 +80,7 @@ rp_mobs.register_mob("rp_mobs_mobs:sheep", {
 				})
 			end
 
+			rp_mobs.init_fall_damage(self, true)
 			rp_mobs.init_breath(self, true, {
 				breath_max = 10,
 				drowning_point = vector.new(0, -0.5, 0.49)
@@ -91,8 +92,8 @@ rp_mobs.register_mob("rp_mobs_mobs:sheep", {
 			rp_mobs.init_tasks(self)
 		end,
 		get_staticdata = rp_mobs.get_staticdata_default,
-		on_step = function(self, dtime)
-			rp_mobs.handle_environment_damage(self, dtime)
+		on_step = function(self, dtime, moveresult)
+			rp_mobs.handle_environment_damage(self, dtime, moveresult)
 			rp_mobs.handle_physics(self)
 			rp_mobs.handle_tasks(self, dtime)
 			rp_mobs.handle_breeding(self, dtime)