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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.
This commit is contained in:
Elias Åström 2020-04-15 14:15:07 +02:00
parent 063595ac3c
commit 1d5c11f683
2 changed files with 267 additions and 0 deletions
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1
mods/CORE/mcl_explosions/description.txt Normal file
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This mod adds a common API to create explosions.

266
mods/CORE/mcl_explosions/init.lua Normal file
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--[[ .__ .__
____ ___ _________ | | ____ _____|__| ____ ____ ______
_/ __ \\ \/ /\____ \| | / _ \/ ___/ |/ _ \ / \ / ___/
\ ___/ > < | |_> > |_( <_> )___ \| ( <_> ) | \\___ \
\___ >__/\_ \| __/|____/\____/____ >__|\____/|___| /____ >
\/ \/|__| \/ \/ \/
Explosion API mod for Minetest (adapted to MineClone 2)
This mod is based on the Minetest explosion API mod, but has been changed
to have the same explosion mechanics as Minecraft and work with MineClone.
The computation-intensive parts of the mod has been optimized to allow for
larger explosions and faster world updating.
This mod was created by Elias Astrom <ryvnf@riseup.net> and is released
under the LGPLv2.1 license.
--]]
mcl_explosions = {}
-- Saved sphere explosion shapes for various radiuses
local sphere_shapes = {}
-- Saved node definitions in table using cid-keys for faster look-up.
local node_br = {}
local AIR_CID = minetest.get_content_id('air')
-- The step length for the rays (Minecraft uses 0.3)
local STEP_LENGTH = 0.3
minetest.after(0, function()
-- Store blast resistance values by content ids to improve performance.
for name, def in pairs(minetest.registered_nodes) do
node_br[minetest.get_content_id(name)] = def._mcl_blast_resistance or 0
end
end)
-- Compute the rays which make up a sphere with radius. Returns a list of rays
-- which can be used to trace explosions. This function is not efficient
-- (especially for larger radiuses), so the generated rays for various radiuses
-- should be cached and reused.
--
-- Should be possible to improve by using a midpoint circle algorithm multiple
-- times to create the sphere, currently uses more of a brute-force approach.
local function compute_sphere_rays(radius)
local rays = {}
local sphere = {}
for y = -radius, radius do
for z = -radius, radius do
for x = -radius, 0, 1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for y = -radius, radius do
for z = -radius, radius do
for x = radius, 0, -1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for x = -radius, radius do
for z = -radius, radius do
for y = -radius, 0, 1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for x = -radius, radius do
for z = -radius, radius do
for y = radius, 0, -1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for x = -radius, radius do
for y = -radius, radius do
for z = -radius, 0, 1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for x = -radius, radius do
for y = -radius, radius do
for z = radius, 0, -1 do
local d = x * x + y * y + z * z
if d <= radius * radius then
local pos = { x = x, y = y, z = z }
sphere[minetest.hash_node_position(pos)] = pos
break
end
end
end
end
for _, pos in pairs(sphere) do
rays[#rays + 1] = vector.normalize(pos)
end
return rays
end
-- Get position from hash. This should be identical to
-- 'minetest.get_position_from_hash' but is used in case the hashing function
-- would change.
local function get_position_from_hash(hash)
local pos = {}
pos.x = (hash % 65536) - 32768
hash = math.floor(hash / 65536)
pos.y = (hash % 65536) - 32768
hash = math.floor(hash / 65536)
pos.z = (hash % 65536) - 32768
return pos
end
-- Traces the rays of an explosion, and updates the environment.
--
-- Parameters:
-- pos - Where the rays in the explosion should start from
-- strength - The strength of each ray
-- raydirs - The directions for each ray
-- radius - The maximum distance each ray will go
-- drop_chance - Chance that destroy nodes drop their items
-- (becomes '1.0 / strength' if unspecified)
--
-- Note that this function has been optimized, it contains code which has been
-- inlined to avoid function calls and unnecessary table creation. This was
-- measured to give a significant performance increase.
local function trace_explode(pos, strength, raydirs, radius, drop_chance)
local vm = minetest.get_voxel_manip()
local emin, emax = vm:read_from_map(vector.subtract(pos, radius),
vector.add(pos, radius))
local emin_x = emin.x
local emin_y = emin.y
local emin_z = emin.z
local ystride = (emax.x - emin_x + 1)
local zstride = ystride * (emax.y - emin_y + 1)
local pos_x = pos.x
local pos_y = pos.y
local pos_z = pos.z
local area = VoxelArea:new {
MinEdge = emin,
MaxEdge = emax
}
local data = vm:get_data()
local destroy = {}
-- Trace rays
for i = 1, #raydirs do
local rpos_x = pos.x
local rpos_y = pos.y
local rpos_z = pos.z
local rdir_x = raydirs[i].x
local rdir_y = raydirs[i].y
local rdir_z = raydirs[i].z
local rstr = (0.7 + math.random() * 0.6) * strength
for r = 0, math.ceil(radius * (1.0 / STEP_LENGTH)) do
local npos_x = math.floor(rpos_x + 0.5)
local npos_y = math.floor(rpos_y + 0.5)
local npos_z = math.floor(rpos_z + 0.5)
local idx = (npos_z - emin_z) * zstride + (npos_y - emin_y) * ystride +
npos_x - emin_x + 1
local cid = data[idx]
local br = node_br[cid]
local hash = (npos_z + 32768) * 65536 * 65536 +
(npos_y + 32768) * 65536 +
npos_x + 32768
rpos_x = rpos_x + STEP_LENGTH * rdir_x
rpos_y = rpos_y + STEP_LENGTH * rdir_y
rpos_z = rpos_z + STEP_LENGTH * rdir_z
rstr = rstr - 0.75 * STEP_LENGTH - (br + 0.3) * STEP_LENGTH
if rstr <= 0 then
break
end
if cid ~= AIR_CID then
destroy[hash] = idx
end
end
end
if drop_chance == nil then
drop_chance = 1 / strength
end
-- Remove destroyed blocks and drop items
for hash, idx in pairs(destroy) do
if math.random() <= drop_chance then
local name = minetest.get_name_from_content_id(data[idx])
local drop = minetest.get_node_drops(name, "")
for _, item in ipairs(drop) do
if type(item) == "string" then
minetest.add_item(get_position_from_hash(hash), item)
end
end
end
data[idx] = AIR_CID
end
-- Log explosion
minetest.log('action', 'Explosion at ' .. minetest.pos_to_string(pos) ..
' with strength ' .. strength .. ' and radius ' .. radius)
-- Update environment
vm:set_data(data)
vm:write_to_map(data)
vm:update_liquids()
end
-- Create an explosion with strength at pos.
--
-- Parameters:
-- pos - The position where the explosion originates from
-- strength - The blast strength of the explosion (a TNT explosion uses 4)
function mcl_explosions.explode(pos, strength)
-- The maximum blast radius (in the air)
local radius = math.ceil(1.3 * strength / (0.3 * 0.75) * 0.3)
if not sphere_shapes[radius] then
sphere_shapes[radius] = compute_sphere_rays(radius)
end
shape = sphere_shapes[radius]
trace_explode(pos, strength, shape, radius)
end