Tnt: Avoid divide-by-zero errors in calc_velocity()

This uses a vmanip to count adjacent tnt nodes and explodes them
all at once, using an inverse square law to recalculate the radius.
The maximum explosion becomes 125 nodes of tnt yielding a radius of
15 nodes, which does not break my machine and makes it return
in under a second.

This makes both bigger explosions and less stability issues.

The drop code has been simplified and now drops at all times a
reasonable amount of drops, never blanketing the area with drops,
even at the larges explosion level.

Particles are scaled up according to explosion size as well - a
bigger explosion will show bigger particles.

To scale the tnt:boom particle, we move it to the _effects() function.

README.txt

@@ -1,4 +1,5 @@
-=== TNT mod for Minetest ===
+Minetest Game mod: tnt
+======================
 by PilzAdam and ShadowNinja
 
 Introduction:

init.lua

@@ -1,4 +1,4 @@
-
+tnt = {}
 -- Default to enabled in singleplayer and disabled in multiplayer
 local singleplayer = minetest.is_singleplayer()
 local setting = minetest.setting_getbool("enable_tnt")
@@ -23,36 +23,48 @@ minetest.after(0, function()
 			name = name,
 			drops = def.drops,
 			flammable = def.groups.flammable,
+			on_blast = def.on_blast,
 		}
 	end
 end)
 
 local function rand_pos(center, pos, radius)
+	local def
+	local reg_nodes = minetest.registered_nodes
+	local i = 0
+	repeat
+		-- Give up and use the center if this takes too long
+		if i > 4 then
+			pos.x, pos.z = center.x, center.z
+			break
+		end
 		pos.x = center.x + math.random(-radius, radius)
 		pos.z = center.z + math.random(-radius, radius)
+		def = reg_nodes[minetest.get_node(pos).name]
+		i = i + 1
+	until def and not def.walkable
 end
 
 local function eject_drops(drops, pos, radius)
 	local drop_pos = vector.new(pos)
 	for _, item in pairs(drops) do
 		local count = item:get_count()
-		local max = item:get_stack_max()
-		if count > max then
-			item:set_count(max)
-		end
 		while count > 0 do
-			if count < max then
-				item:set_count(count)
-			end
+			local take = math.max(1,math.min(radius * radius,
+					count,
+					item:get_stack_max()))
 			rand_pos(pos, drop_pos, radius)
-			local obj = minetest.add_item(drop_pos, item)
+			local dropitem = ItemStack(item)
+			dropitem:set_count(take)
+			local obj = minetest.add_item(drop_pos, dropitem)
 			if obj then
 				obj:get_luaentity().collect = true
-				obj:setacceleration({x=0, y=-10, z=0})
-				obj:setvelocity({x=math.random(-3, 3), y=10,
-						z=math.random(-3, 3)})
+				obj:setacceleration({x = 0, y = -10, z = 0})
+				obj:setvelocity({x = math.random(-3, 3),
+						y = math.random(0, 10),
+						z = math.random(-3, 3)})
 			end
-			count = count - max
+			count = count - take
 		end
 	end
 end
@@ -72,28 +84,37 @@ local function add_drop(drops, item)
 	end
 end
 
-local fire_node = {name="fire:basic_flame"}
 
-local function destroy(drops, pos, cid)
-	if minetest.is_protected(pos, "") then
-		return
+local function destroy(drops, npos, cid, c_air, c_fire, on_blast_queue, ignore_protection, ignore_on_blast)
+	if not ignore_protection and minetest.is_protected(npos, "") then
+		return cid
 	end
+
 	local def = cid_data[cid]
-	if def and def.flammable then
-		minetest.set_node(pos, fire_node)
+
+	if not def then
+		return c_air
+	elseif not ignore_on_blast and def.on_blast then
+		on_blast_queue[#on_blast_queue + 1] = {pos = vector.new(npos), on_blast = def.on_blast}
+		return cid
+	elseif def.flammable then
+		return c_fire
 	else
-		minetest.remove_node(pos)
-		if def then
 		local node_drops = minetest.get_node_drops(def.name, "")
 		for _, item in ipairs(node_drops) do
 			add_drop(drops, item)
 		end
-		end
+		return c_air
 	end
 end
 
 
 local function calc_velocity(pos1, pos2, old_vel, power)
+	-- Avoid errors caused by a vector of zero length
+	if vector.equals(pos1, pos2) then
+		return old_vel
+	end
+
 	local vel = vector.direction(pos1, pos2)
 	vel = vector.normalize(vel)
 	vel = vector.multiply(vel, power)
@@ -105,61 +126,179 @@ local function calc_velocity(pos1, pos2, old_vel, power)
 
 	-- Add old velocity
 	vel = vector.add(vel, old_vel)
+
+	-- randomize it a bit
+	vel = vector.add(vel, {
+		x = math.random() - 0.5,
+		y = math.random() - 0.5,
+		z = math.random() - 0.5,
+	})
+
+	-- Limit to terminal velocity
+	dist = vector.length(vel)
+	if dist > 250 then
+		vel = vector.divide(vel, dist / 250)
+	end
 	return vel
 end
 
-local function entity_physics(pos, radius)
-	-- Make the damage radius larger than the destruction radius
-	radius = radius * 2
+local function entity_physics(pos, radius, drops)
 	local objs = minetest.get_objects_inside_radius(pos, radius)
 	for _, obj in pairs(objs) do
 		local obj_pos = obj:getpos()
-		local obj_vel = obj:getvelocity()
 		local dist = math.max(1, vector.distance(pos, obj_pos))
 
-		if obj_vel ~= nil then
+		local damage = (4 / dist) * radius
+		if obj:is_player() then
+			-- currently the engine has no method to set
+			-- player velocity. See #2960
+			-- instead, we knock the player back 1.0 node, and slightly upwards
+			local dir = vector.normalize(vector.subtract(obj_pos, pos))
+			local moveoff = vector.multiply(dir, dist + 1.0)
+			local newpos = vector.add(pos, moveoff)
+			local newpos = vector.add(newpos, {x = 0, y = 0.2, z = 0})
+			obj:setpos(newpos)
+
+			obj:set_hp(obj:get_hp() - damage)
+		else
+			local do_damage = true
+			local do_knockback = true
+			local entity_drops = {}
+			local luaobj = obj:get_luaentity()
+			local objdef = minetest.registered_entities[luaobj.name]
+
+			if objdef and objdef.on_blast then
+				do_damage, do_knockback, entity_drops = objdef.on_blast(luaobj, damage)
+			end
+
+			if do_knockback then
+				local obj_vel = obj:getvelocity()
 				obj:setvelocity(calc_velocity(pos, obj_pos,
 						obj_vel, radius * 10))
 			end
-
-		local damage = (4 / dist) * radius
-		obj:set_hp(obj:get_hp() - damage)
+			if do_damage then
+				if not obj:get_armor_groups().immortal then
+					obj:punch(obj, 1.0, {
+						full_punch_interval = 1.0,
+						damage_groups = {fleshy = damage},
+					}, nil)
+				end
+			end
+			for _, item in ipairs(entity_drops) do
+				add_drop(drops, item)
+			end
+		end
 	end
 end
 
-local function add_effects(pos, radius)
+local function add_effects(pos, radius, drops)
+	minetest.add_particle({
+		pos = pos,
+		velocity = vector.new(),
+		acceleration = vector.new(),
+		expirationtime = 0.4,
+		size = radius * 10,
+		collisiondetection = false,
+		vertical = false,
+		texture = "tnt_boom.png",
+	})
 	minetest.add_particlespawner({
-		amount = 128,
-		time = 1,
+		amount = 64,
+		time = 0.5,
 		minpos = vector.subtract(pos, radius / 2),
 		maxpos = vector.add(pos, radius / 2),
-		minvel = {x=-20, y=-20, z=-20},
-		maxvel = {x=20,  y=20,  z=20},
+		minvel = {x = -10, y = -10, z = -10},
+		maxvel = {x = 10, y = 10, z = 10},
 		minacc = vector.new(),
 		maxacc = vector.new(),
 		minexptime = 1,
-		maxexptime = 3,
-		minsize = 8,
-		maxsize = 16,
+		maxexptime = 2.5,
+		minsize = radius * 3,
+		maxsize = radius * 5,
 		texture = "tnt_smoke.png",
 	})
+
+	-- we just dropped some items. Look at the items entities and pick
+	-- one of them to use as texture
+	local texture = "tnt_blast.png" --fallback texture
+	local most = 0
+	for name, stack in pairs(drops) do
+		local count = stack:get_count()
+		if count > most then
+			most = count
+			local def = minetest.registered_nodes[name]
+			if def and def.tiles and def.tiles[1] then
+				texture = def.tiles[1]
+			end
+		end
+	end
+
+	minetest.add_particlespawner({
+		amount = 64,
+		time = 0.1,
+		minpos = vector.subtract(pos, radius / 2),
+		maxpos = vector.add(pos, radius / 2),
+		minvel = {x = -3, y = 0, z = -3},
+		maxvel = {x = 3, y = 5,  z = 3},
+		minacc = {x = 0, y = -10, z = 0},
+		maxacc = {x = 0, y = -10, z = 0},
+		minexptime = 0.8,
+		maxexptime = 2.0,
+		minsize = radius * 0.66,
+		maxsize = radius * 2,
+		texture = texture,
+		collisiondetection = true,
+	})
 end
 
-local function burn(pos)
+function tnt.burn(pos)
 	local name = minetest.get_node(pos).name
-	if name == "tnt:tnt" then
-		minetest.sound_play("tnt_ignite", {pos=pos})
-		minetest.set_node(pos, {name="tnt:tnt_burning"})
+	local group = minetest.get_item_group(name, "tnt")
+	if group > 0 then
+		minetest.sound_play("tnt_ignite", {pos = pos})
+		minetest.set_node(pos, {name = name .. "_burning"})
 		minetest.get_node_timer(pos):start(1)
 	elseif name == "tnt:gunpowder" then
-		minetest.sound_play("tnt_gunpowder_burning", {pos=pos, gain=2})
-		minetest.set_node(pos, {name="tnt:gunpowder_burning"})
-		minetest.get_node_timer(pos):start(1)
+		minetest.set_node(pos, {name = "tnt:gunpowder_burning"})
 	end
 end
 
-local function explode(pos, radius)
+local function tnt_explode(pos, radius, ignore_protection, ignore_on_blast)
 	local pos = vector.round(pos)
+	-- scan for adjacent TNT nodes first, and enlarge the explosion
+	local vm1 = VoxelManip()
+	local p1 = vector.subtract(pos, 2)
+	local p2 = vector.add(pos, 2)
+	local minp, maxp = vm1:read_from_map(p1, p2)
+	local a = VoxelArea:new({MinEdge = minp, MaxEdge = maxp})
+	local data = vm1:get_data()
+	local count = 0
+	local c_tnt = minetest.get_content_id("tnt:tnt")
+	local c_tnt_burning = minetest.get_content_id("tnt:tnt_burning")
+	local c_tnt_boom = minetest.get_content_id("tnt:boom")
+	local c_air = minetest.get_content_id("air")
+
+	for z = pos.z - 2, pos.z + 2 do
+	for y = pos.y - 2, pos.y + 2 do
+		local vi = a:index(pos.x - 2, y, z)
+		for x = pos.x - 2, pos.x + 2 do
+			local cid = data[vi]
+			if cid == c_tnt or cid == c_tnt_boom or cid == c_tnt_burning then
+				count = count + 1
+				data[vi] = c_air
+			end
+			vi = vi + 1
+		end
+	end
+	end
+
+	vm1:set_data(data)
+	vm1:write_to_map()
+
+	-- recalculate new radius
+	radius = math.floor(radius * math.pow(count, 1/3))
+
+	-- perform the explosion
 	local vm = VoxelManip()
 	local pr = PseudoRandom(os.time())
 	local p1 = vector.subtract(pos, radius)
@@ -169,34 +308,21 @@ local function explode(pos, radius)
 	local data = vm:get_data()
 
 	local drops = {}
-	local p = {}
+	local on_blast_queue = {}
 
-	local c_air = minetest.get_content_id("air")
-	local c_tnt = minetest.get_content_id("tnt:tnt")
-	local c_tnt_burning = minetest.get_content_id("tnt:tnt_burning")
-	local c_gunpowder = minetest.get_content_id("tnt:gunpowder")
-	local c_gunpowder_burning = minetest.get_content_id("tnt:gunpowder_burning")
-	local c_boom = minetest.get_content_id("tnt:boom")
 	local c_fire = minetest.get_content_id("fire:basic_flame")
-
 	for z = -radius, radius do
 	for y = -radius, radius do
 	local vi = a:index(pos.x + (-radius), pos.y + y, pos.z + z)
 	for x = -radius, radius do
-		if (x * x) + (y * y) + (z * z) <=
-				(radius * radius) + pr:next(-radius, radius) then
+		local r = vector.length(vector.new(x, y, z))
+		if (radius * radius) / (r * r) >= (pr:next(80, 125) / 100) then
 			local cid = data[vi]
-			p.x = pos.x + x
-			p.y = pos.y + y
-			p.z = pos.z + z
-			if cid == c_tnt or cid == c_gunpowder then
-				burn(p)
-			elseif cid ~= c_tnt_burning and
-					cid ~= c_gunpowder_burning and
-					cid ~= c_air and
-					cid ~= c_fire and
-					cid ~= c_boom then
-				destroy(drops, p, cid)
+			local p = {x = pos.x + x, y = pos.y + y, z = pos.z + z}
+			if cid ~= c_air then
+				data[vi] = destroy(drops, p, cid, c_air, c_fire,
+					on_blast_queue, ignore_protection,
+					ignore_on_blast)
 			end
 		end
 		vi = vi + 1
@@ -204,87 +330,93 @@ local function explode(pos, radius)
 	end
 	end
 
-	return drops
-end
+	vm:set_data(data)
+	vm:write_to_map()
+	vm:update_map()
+	vm:update_liquids()
 
-
-local function boom(pos)
-	minetest.sound_play("tnt_explode", {pos=pos, gain=1.5, max_hear_distance=2*64})
-	minetest.set_node(pos, {name="tnt:boom"})
-	minetest.get_node_timer(pos):start(0.5)
-
-	local drops = explode(pos, radius)
-	entity_physics(pos, radius)
-	eject_drops(drops, pos, radius)
-	add_effects(pos, radius)
-end
-
-minetest.register_node("tnt:tnt", {
-	description = "TNT",
-	tiles = {"tnt_top.png", "tnt_bottom.png", "tnt_side.png"},
-	groups = {dig_immediate=2, mesecon=2},
-	sounds = default.node_sound_wood_defaults(),
-	on_punch = function(pos, node, puncher)
-		if puncher:get_wielded_item():get_name() == "default:torch" then
-			minetest.sound_play("tnt_ignite", {pos=pos})
-			minetest.set_node(pos, {name="tnt:tnt_burning"})
-			minetest.get_node_timer(pos):start(4)
+	-- call nodeupdate for everything within 1.5x blast radius
+	for z = -radius * 1.5, radius * 1.5 do
+	for x = -radius * 1.5, radius * 1.5 do
+	for y = -radius * 1.5, radius * 1.5 do
+		local s = vector.add(pos, {x = x, y = y, z = z})
+		local r = vector.distance(pos, s)
+		if r / radius < 1.4 then
+			nodeupdate(s)
+		end
+	end
+	end
 	end
-	end,
-	mesecons = {effector = {action_on = boom}},
-})
 
-minetest.register_node("tnt:tnt_burning", {
-	tiles = {
-		{
-			name = "tnt_top_burning_animated.png",
-			animation = {
-				type = "vertical_frames",
-				aspect_w = 16,
-				aspect_h = 16,
-				length = 1,
-			}
-		},
-		"tnt_bottom.png", "tnt_side.png"},
-	light_source = 5,
-	drop = "",
-	sounds = default.node_sound_wood_defaults(),
-	on_timer = boom,
-})
+	for _, data in ipairs(on_blast_queue) do
+		local dist = math.max(1, vector.distance(data.pos, pos))
+		local intensity = (radius * radius) / (dist * dist)
+		local node_drops = data.on_blast(data.pos, intensity)
+		if node_drops then
+			for _, item in ipairs(node_drops) do
+				add_drop(drops, item)
+			end
+		end
+	end
+
+	return drops, radius
+end
+
+function tnt.boom(pos, def)
+	minetest.sound_play("tnt_explode", {pos = pos, gain = 1.5, max_hear_distance = 2*64})
+	minetest.set_node(pos, {name = "tnt:boom"})
+	local drops, radius = tnt_explode(pos, def.radius, def.ignore_protection,
+			def.ignore_on_blast)
+	-- append entity drops
+	local damage_radius = (radius / def.radius) * def.damage_radius
+	entity_physics(pos, damage_radius, drops)
+	if not def.disable_drops then
+		eject_drops(drops, pos, radius)
+	end
+	add_effects(pos, radius, drops)
+end
 
 minetest.register_node("tnt:boom", {
-	drawtype = "plantlike",
-	tiles = {"tnt_boom.png"},
-	light_source = LIGHT_MAX,
+	drawtype = "airlike",
+	light_source = default.LIGHT_MAX,
 	walkable = false,
 	drop = "",
-	groups = {dig_immediate=3},
+	groups = {dig_immediate = 3},
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(0.4)
+	end,
 	on_timer = function(pos, elapsed)
 		minetest.remove_node(pos)
 	end,
+	-- unaffected by explosions
+	on_blast = function() end,
 })
 
 minetest.register_node("tnt:gunpowder", {
 	description = "Gun Powder",
 	drawtype = "raillike",
 	paramtype = "light",
+	is_ground_content = false,
 	sunlight_propagates = true,
 	walkable = false,
-	tiles = {"tnt_gunpowder.png",},
+	tiles = {"tnt_gunpowder_straight.png", "tnt_gunpowder_curved.png", "tnt_gunpowder_t_junction.png", "tnt_gunpowder_crossing.png"},
 	inventory_image = "tnt_gunpowder_inventory.png",
 	wield_image = "tnt_gunpowder_inventory.png",
 	selection_box = {
 		type = "fixed",
 		fixed = {-1/2, -1/2, -1/2, 1/2, -1/2+1/16, 1/2},
 	},
-	groups = {dig_immediate=2,attached_node=1},
+	groups = {dig_immediate = 2, attached_node = 1, connect_to_raillike = minetest.raillike_group("gunpowder")},
 	sounds = default.node_sound_leaves_defaults(),
 
 	on_punch = function(pos, node, puncher)
 		if puncher:get_wielded_item():get_name() == "default:torch" then
-			burn(pos)
+			tnt.burn(pos)
 		end
 	end,
+	on_blast = function(pos, intensity)
+		tnt.burn(pos)
+	end,
 })
 
 minetest.register_node("tnt:gunpowder_burning", {
@@ -294,7 +426,34 @@ minetest.register_node("tnt:gunpowder_burning", {
 	walkable = false,
 	light_source = 5,
 	tiles = {{
-		name = "tnt_gunpowder_burning_animated.png",
+		name = "tnt_gunpowder_burning_straight_animated.png",
+		animation = {
+			type = "vertical_frames",
+			aspect_w = 16,
+			aspect_h = 16,
+			length = 1,
+		}
+	},
+	{
+		name = "tnt_gunpowder_burning_curved_animated.png",
+		animation = {
+			type = "vertical_frames",
+			aspect_w = 16,
+			aspect_h = 16,
+			length = 1,
+		}
+	},
+	{
+		name = "tnt_gunpowder_burning_t_junction_animated.png",
+		animation = {
+			type = "vertical_frames",
+			aspect_w = 16,
+			aspect_h = 16,
+			length = 1,
+		}
+	},
+	{
+		name = "tnt_gunpowder_burning_crossing_animated.png",
 		animation = {
 			type = "vertical_frames",
 			aspect_w = 16,
@@ -307,14 +466,14 @@ minetest.register_node("tnt:gunpowder_burning", {
 		fixed = {-1/2, -1/2, -1/2, 1/2, -1/2+1/16, 1/2},
 	},
 	drop = "",
-	groups = {dig_immediate=2,attached_node=1},
+	groups = {dig_immediate = 2, attached_node = 1, connect_to_raillike = minetest.raillike_group("gunpowder")},
 	sounds = default.node_sound_leaves_defaults(),
 	on_timer = function(pos, elapsed)
 		for dx = -1, 1 do
 		for dz = -1, 1 do
 		for dy = -1, 1 do
 			if not (dx == 0 and dz == 0) then
-				burn({
+				tnt.burn({
 					x = pos.x + dx,
 					y = pos.y + dy,
 					z = pos.z + dz,
@@ -324,15 +483,21 @@ minetest.register_node("tnt:gunpowder_burning", {
 		end
 		end
 		minetest.remove_node(pos)
-	end
+	end,
+	-- unaffected by explosions
+	on_blast = function() end,
+	on_construct = function(pos)
+		minetest.sound_play("tnt_gunpowder_burning", {pos = pos, gain = 2})
+		minetest.get_node_timer(pos):start(1)
+	end,
 })
 
 minetest.register_abm({
-	nodenames = {"tnt:tnt", "tnt:gunpowder"},
+	nodenames = {"group:tnt", "tnt:gunpowder"},
 	neighbors = {"fire:basic_flame", "default:lava_source", "default:lava_flowing"},
-	interval = 1,
+	interval = 4,
 	chance = 1,
-	action = burn,
+	action = tnt.burn,
 })
 
 minetest.register_craft({
@@ -350,7 +515,79 @@ minetest.register_craft({
 	}
 })
 
-if minetest.setting_get("log_mods") then
-	minetest.debug("[TNT] Loaded!")
+function tnt.register_tnt(def)
+	local name = ""
+	if not def.name:find(':') then
+		name = "tnt:" .. def.name
+	else
+		name = def.name
+		def.name = def.name:match(":([%w_]+)")
+	end
+	if not def.tiles then def.tiles = {} end
+	local tnt_top = def.tiles.top or def.name .. "_top.png"
+	local tnt_bottom = def.tiles.bottom or def.name .. "_bottom.png"
+	local tnt_side = def.tiles.side or def.name .. "_side.png"
+	local tnt_burning = def.tiles.burning or def.name .. "_top_burning_animated.png"
+	if not def.damage_radius then def.damage_radius = def.radius * 2 end
+
+	minetest.register_node(":" .. name, {
+		description = def.description,
+		tiles = {tnt_top, tnt_bottom, tnt_side},
+		is_ground_content = false,
+		groups = {dig_immediate = 2, mesecon = 2, tnt = 1},
+		sounds = default.node_sound_wood_defaults(),
+		on_punch = function(pos, node, puncher)
+			if puncher:get_wielded_item():get_name() == "default:torch" then
+				minetest.set_node(pos, {name = name .. "_burning"})
+			end
+		end,
+		on_blast = function(pos, intensity)
+			minetest.after(0.1, function()
+				tnt.boom(pos, def)
+			end)
+		end,
+		mesecons = {effector =
+			{action_on =
+				function(pos)
+					tnt.boom(pos, def)
+				end
+			}
+		},
+	})
+
+	minetest.register_node(":" .. name .. "_burning", {
+		tiles = {
+			{
+				name = tnt_burning,
+				animation = {
+					type = "vertical_frames",
+					aspect_w = 16,
+					aspect_h = 16,
+					length = 1,
+				}
+			},
+			tnt_bottom, tnt_side
+			},
+		light_source = 5,
+		drop = "",
+		sounds = default.node_sound_wood_defaults(),
+		groups = {falling_node = 1},
+		on_timer = function(pos, elapsed)
+			tnt.boom(pos, def)
+		end,
+		-- unaffected by explosions
+		on_blast = function() end,
+		on_construct = function(pos)
+			minetest.sound_play("tnt_ignite", {pos = pos})
+			minetest.get_node_timer(pos):start(4)
+			nodeupdate(pos)
+		end,
+	})
 end
 
+tnt.register_tnt({
+	name = "tnt:tnt",
+	description = "TNT",
+	radius = radius,
+})
+