-- thegrid 0.2.1 by paramat
-- For latest stable Minetest and back to 0.4.8
-- Depends default
-- License: code WTFPL

-- Parameters

local YMIN    = 5000 -- Approximate base of realm
local TERCEN  = 5500 -- Terrain centre y, average surface level
local YMAX    = 6000 -- Approximate top of atmosphere
local TERSCA  =   64 -- Terrain scale in nodes, controls height of mountains
local BLEND   =   40 -- Flat to rough blend distance in nodes
local FLATRAD =  345 -- Flat area radius in nodes

-- White grid limits in units of chunk (chunk = 80 nodes)
local WXMIN = -3
local WXMAX = -1
local WZMIN = -3
local WZMAX = -1
-- Orange grid
local OXMIN = -3
local OXMAX = -1
local OZMIN = 0
local OZMAX = 2
-- Blue grid
local BXMIN = 0
local BXMAX = 2
local BZMIN = -3
local BZMAX = -1
-- Green grid
local GXMIN = 0
local GXMAX = 2
local GZMIN = 0
local GZMAX = 2

-- 3D noise for terrain

local np_terrain = {
    offset = 0,
    scale = 1,
    spread = {x=512, y=256, z=512}, -- scale of largest structures
    seed = -230023, -- any number, defines the terrain pattern like a seed growing into a plant
    octaves = 6, -- level of finest detail, 5 = smoother
    persist = 0.63 -- balance of fine detail relative to coarse detail
}           -- 0.4 = smooth, 0.6 = rough and Minetest default
            -- 0.67 = science fiction, more overhangs and floating rocks

-- Stuff

thegrid = {}

-- On generated function

minetest.register_on_generated(function(minp, maxp, seed)
    if minp.y < YMIN or maxp.y > YMAX then
        return
    end

    local t1 = os.clock()
    local x1 = maxp.x
    local y1 = maxp.y
    local z1 = maxp.z
    local x0 = minp.x
    local y0 = minp.y
    local z0 = minp.z
    local chux = (x0 + 32) / 80 -- co-ordinates in chunks, chunk zero is x/z = -32 to x/z = 47
    local chuz = (z0 + 32) / 80

    print ("[thegrid] chunk minp ("..x0.." "..y0.." "..z0..")")

    local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
    local area = VoxelArea:new{MinEdge=emin, MaxEdge=emax}
    local data = vm:get_data()

    local c_air = minetest.get_content_id("air")
    local c_tronstone = minetest.get_content_id("tronblocks:stone")
    local c_tile = minetest.get_content_id("tronblocks:tile")
    local c_tileor = minetest.get_content_id("tronblocks:tile_orange")
    local c_tilebl = minetest.get_content_id("tronblocks:tile_blue")
    local c_tilegr = minetest.get_content_id("tronblocks:tile_green")

    local sidelen = x1 - x0 + 1
    local chulens = {x=sidelen, y=sidelen, z=sidelen}
    local minpos = {x=x0, y=y0, z=z0}

    local nvals_terrain = minetest.get_perlin_map(np_terrain, chulens):get3dMap_flat(minpos)

    local ni = 1
    for z = z0, z1 do -- for each xy plane progressing northwards
        for y = y0, y1 do -- for each x row progressing upwards
            local vi = area:index(x0, y, z) -- get voxel index for first node in x row
            for x = x0, x1 do -- for each node do
                local nodrad = math.sqrt((x + 32) ^ 2 + (z + 32) ^ 2) -- centre is at -32 -32
                local grad = (TERCEN - y) / TERSCA
                local namp
                if nodrad > FLATRAD + BLEND then
                    namp = 1
                elseif nodrad < FLATRAD then
                    namp = 0
                else
                    namp = (1 - math.cos((nodrad - FLATRAD) / BLEND * math.pi)) / 2
                end
                local n_terrain = nvals_terrain[ni]
                local density = (n_terrain ^ 2 + n_terrain * 0.5) * namp + grad
                if namp == 0 and y == TERCEN then
                    if chux >= WXMIN and chux <= WXMAX and chuz >= WZMIN and chuz <= WZMAX then
                        data[vi] = c_tile
                    elseif chux >= OXMIN and chux <= OXMAX and chuz >= OZMIN and chuz <= OZMAX then
                        data[vi] = c_tileor
                    elseif chux >= BXMIN and chux <= BXMAX and chuz >= BZMIN and chuz <= BZMAX then
                        data[vi] = c_tilebl
                    elseif chux >= GXMIN and chux <= GXMAX and chuz >= GZMIN and chuz <= GZMAX then
                        data[vi] = c_tilegr
                    else
                        data[vi] = c_tronstone
                    end
                elseif density >= 0 then
                    data[vi] = c_tronstone
                else
                    data[vi] = c_air
                end
                ni = ni + 1 -- increment perlinmap noise index
                vi = vi + 1 -- increment voxel index along x row
            end
        end
    end

    vm:set_data(data)
    vm:set_lighting({day=0, night=0})
    vm:calc_lighting()
    vm:write_to_map(data)
    local chugent = math.ceil((os.clock() - t1) * 1000)
    print ("[thegrid] "..chugent.." ms")
end)