Add mcl_explosions for ray traced explosions
Code has been adapted from the Minetest explosions API mod to have Minecraft-like explosion mechanics and work with MineClone 2.objects
Elias Åström
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1d5c11f683
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This mod adds a common API to create explosions.
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--[[ .__ .__
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____ ___ _________ | | ____ _____|__| ____ ____ ______
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_/ __ \\ \/ /\____ \| | / _ \/ ___/ |/ _ \ / \ / ___/
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\ ___/ > < | |_> > |_( <_> )___ \| ( <_> ) | \\___ \
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\___ >__/\_ \| __/|____/\____/____ >__|\____/|___| /____ >
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\/ \/|__| \/ \/ \/
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Explosion API mod for Minetest (adapted to MineClone 2)
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This mod is based on the Minetest explosion API mod, but has been changed
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to have the same explosion mechanics as Minecraft and work with MineClone.
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The computation-intensive parts of the mod has been optimized to allow for
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larger explosions and faster world updating.
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This mod was created by Elias Astrom <ryvnf@riseup.net> and is released
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under the LGPLv2.1 license.
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--]]
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mcl_explosions = {}
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-- Saved sphere explosion shapes for various radiuses
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local sphere_shapes = {}
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-- Saved node definitions in table using cid-keys for faster look-up.
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local node_br = {}
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local AIR_CID = minetest.get_content_id('air')
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-- The step length for the rays (Minecraft uses 0.3)
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local STEP_LENGTH = 0.3
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minetest.after(0, function()
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-- Store blast resistance values by content ids to improve performance.
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for name, def in pairs(minetest.registered_nodes) do
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node_br[minetest.get_content_id(name)] = def._mcl_blast_resistance or 0
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end
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end)
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-- Compute the rays which make up a sphere with radius. Returns a list of rays
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-- which can be used to trace explosions. This function is not efficient
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-- (especially for larger radiuses), so the generated rays for various radiuses
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-- should be cached and reused.
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--
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-- Should be possible to improve by using a midpoint circle algorithm multiple
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-- times to create the sphere, currently uses more of a brute-force approach.
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local function compute_sphere_rays(radius)
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local rays = {}
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local sphere = {}
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for y = -radius, radius do
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for z = -radius, radius do
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for x = -radius, 0, 1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for y = -radius, radius do
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for z = -radius, radius do
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for x = radius, 0, -1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for x = -radius, radius do
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for z = -radius, radius do
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for y = -radius, 0, 1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for x = -radius, radius do
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for z = -radius, radius do
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for y = radius, 0, -1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for x = -radius, radius do
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for y = -radius, radius do
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for z = -radius, 0, 1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for x = -radius, radius do
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for y = -radius, radius do
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for z = radius, 0, -1 do
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local d = x * x + y * y + z * z
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if d <= radius * radius then
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local pos = { x = x, y = y, z = z }
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sphere[minetest.hash_node_position(pos)] = pos
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break
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end
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end
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end
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end
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for _, pos in pairs(sphere) do
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rays[#rays + 1] = vector.normalize(pos)
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end
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return rays
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end
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-- Get position from hash. This should be identical to
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-- 'minetest.get_position_from_hash' but is used in case the hashing function
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-- would change.
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local function get_position_from_hash(hash)
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local pos = {}
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pos.x = (hash % 65536) - 32768
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hash = math.floor(hash / 65536)
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pos.y = (hash % 65536) - 32768
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hash = math.floor(hash / 65536)
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pos.z = (hash % 65536) - 32768
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return pos
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end
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-- Traces the rays of an explosion, and updates the environment.
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--
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-- Parameters:
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-- pos - Where the rays in the explosion should start from
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-- strength - The strength of each ray
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-- raydirs - The directions for each ray
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-- radius - The maximum distance each ray will go
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-- drop_chance - Chance that destroy nodes drop their items
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-- (becomes '1.0 / strength' if unspecified)
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--
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-- Note that this function has been optimized, it contains code which has been
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-- inlined to avoid function calls and unnecessary table creation. This was
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-- measured to give a significant performance increase.
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local function trace_explode(pos, strength, raydirs, radius, drop_chance)
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local vm = minetest.get_voxel_manip()
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local emin, emax = vm:read_from_map(vector.subtract(pos, radius),
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vector.add(pos, radius))
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local emin_x = emin.x
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local emin_y = emin.y
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local emin_z = emin.z
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local ystride = (emax.x - emin_x + 1)
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local zstride = ystride * (emax.y - emin_y + 1)
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local pos_x = pos.x
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local pos_y = pos.y
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local pos_z = pos.z
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local area = VoxelArea:new {
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MinEdge = emin,
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MaxEdge = emax
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}
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local data = vm:get_data()
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local destroy = {}
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-- Trace rays
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for i = 1, #raydirs do
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local rpos_x = pos.x
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local rpos_y = pos.y
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local rpos_z = pos.z
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local rdir_x = raydirs[i].x
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local rdir_y = raydirs[i].y
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local rdir_z = raydirs[i].z
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local rstr = (0.7 + math.random() * 0.6) * strength
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for r = 0, math.ceil(radius * (1.0 / STEP_LENGTH)) do
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local npos_x = math.floor(rpos_x + 0.5)
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local npos_y = math.floor(rpos_y + 0.5)
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local npos_z = math.floor(rpos_z + 0.5)
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local idx = (npos_z - emin_z) * zstride + (npos_y - emin_y) * ystride +
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npos_x - emin_x + 1
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local cid = data[idx]
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local br = node_br[cid]
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local hash = (npos_z + 32768) * 65536 * 65536 +
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(npos_y + 32768) * 65536 +
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npos_x + 32768
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rpos_x = rpos_x + STEP_LENGTH * rdir_x
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rpos_y = rpos_y + STEP_LENGTH * rdir_y
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rpos_z = rpos_z + STEP_LENGTH * rdir_z
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rstr = rstr - 0.75 * STEP_LENGTH - (br + 0.3) * STEP_LENGTH
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if rstr <= 0 then
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break
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end
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if cid ~= AIR_CID then
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destroy[hash] = idx
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end
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end
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end
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if drop_chance == nil then
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drop_chance = 1 / strength
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end
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-- Remove destroyed blocks and drop items
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for hash, idx in pairs(destroy) do
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if math.random() <= drop_chance then
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local name = minetest.get_name_from_content_id(data[idx])
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local drop = minetest.get_node_drops(name, "")
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for _, item in ipairs(drop) do
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if type(item) == "string" then
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minetest.add_item(get_position_from_hash(hash), item)
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end
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end
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end
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data[idx] = AIR_CID
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end
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-- Log explosion
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minetest.log('action', 'Explosion at ' .. minetest.pos_to_string(pos) ..
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' with strength ' .. strength .. ' and radius ' .. radius)
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-- Update environment
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vm:set_data(data)
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vm:write_to_map(data)
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vm:update_liquids()
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end
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-- Create an explosion with strength at pos.
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--
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-- Parameters:
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-- pos - The position where the explosion originates from
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-- strength - The blast strength of the explosion (a TNT explosion uses 4)
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function mcl_explosions.explode(pos, strength)
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-- The maximum blast radius (in the air)
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local radius = math.ceil(1.3 * strength / (0.3 * 0.75) * 0.3)
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if not sphere_shapes[radius] then
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sphere_shapes[radius] = compute_sphere_rays(radius)
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end
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shape = sphere_shapes[radius]
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trace_explode(pos, strength, shape, radius)
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end
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