Fix creeper explosions only doing 1/2 heart damage

The solution was to move the creeper explosions to originate from the
center of the creepers collisionbox and not its entity position.

mods/CORE/mcl_util/init.lua

@@ -395,4 +395,13 @@ function mcl_util.generate_on_place_plant_function(condition)
 	end
 end
 
-
+-- adjust the y level of an object to the center of its collisionbox
+-- used to get the origin position of entity explosions
+function mcl_util.get_object_center(obj)
+	local collisionbox = obj:get_properties().collisionbox
+	local pos = obj:get_pos()
+	local ymin = collisionbox[2]
+	local ymax = collisionbox[5]
+	pos.y = pos.y + (ymax - ymin) / 2.0
+	return pos
+end

mods/ENTITIES/mcl_mobs/api.lua

@@ -2258,7 +2258,6 @@ local dogswitch = function(self, dtime)
 	return self.dogshoot_switch
 end
 
-
 -- execute current state (stand, walk, run, attacks)
 -- returns true if mob has died
 local do_states = function(self, dtime)
@@ -2550,7 +2549,7 @@ local do_states = function(self, dtime)
 
 					if mod_explosions then
 					if mobs_griefing and not minetest.is_protected(pos, "") then
-						mcl_explosions.explode(self.object:get_pos(), self.explosion_strength, { drop_chance = 1.0 }, self.object)
+						mcl_explosions.explode(mcl_util.get_object_center(self.object), self.explosion_strength, { drop_chance = 1.0 }, self.object)
 					else
 						minetest.sound_play(self.sounds.explode, {
 							pos = pos,

mods/ENTITIES/mobs_mc/creeper.lua

@@ -71,7 +71,7 @@ mobs:register_mob("mobs_mc:creeper", {
 		if self._forced_explosion_countdown_timer ~= nil then
 			self._forced_explosion_countdown_timer = self._forced_explosion_countdown_timer - dtime
 			if self._forced_explosion_countdown_timer <= 0 then
-				mobs:boom(self, self.object:get_pos(), self.explosion_strength)
+				mobs:boom(self, mcl_util.get_object_center(self.object), self.explosion_strength)
 				self.object:remove()
 			end
 		end