nether/mapgen_geodes.lua

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2023-01-26 15:59:05 +01:00
--[[
Nether mod for minetest
This file contains helper functions for generating geode interiors,
a proof-of-concept to demonstrate how the secondary/spare region
in the nether might be put to use by someone.
Copyright (C) 2021 Treer
Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
]]--
local debugf = nether.debug
local mapgen = nether.mapgen
-- Content ids
local c_air = minetest.get_content_id("air")
local c_crystal = minetest.get_content_id("nether:geodelite") -- geodelite has a faint glow
local c_netherrack = minetest.get_content_id("nether:rack")
local c_glowstone = minetest.get_content_id("nether:glowstone")
-- Math funcs
local math_max, math_min, math_abs, math_floor, math_pi = math.max, math.min, math.abs, math.floor, math.pi -- avoid needing table lookups each time a common math function is invoked
-- Create a tiling space of close-packed spheres, using Hexagonal close packing
-- of spheres with radius 0.5.
-- With a layer of spheres on a flat surface, if the pack-z distance is 1 due to 0.5
-- radius then the pack-x distance will be the height of an equilateral triangle: sqrt(3) / 2,
-- and the pack-y distance between each layer will be sqrt(6) / 3,
-- The tessellating space will be a rectangular box of 2*pack-x by 1*pack-z by 3*pack-y
local xPack = math.sqrt(3)/2 -- 0.866, height of an equalateral triangle
local xPack2 = xPack * 2 -- 1.732
local yPack = math.sqrt(6) / 3 -- 0.816, y height of each layer
local yPack2 = yPack * 2
local yPack3 = yPack * 3
local layer2offsetx = xPack / 3 -- 0.289, height to center of equalateral triangle
local layer3offsetx = xPack2 / 3 -- 0.577
local structureSize = 50 -- magic numbers may need retuning if this changes too much
local layer1 = {
{0, 0, 0},
{0, 0, 1},
{xPack, 0, -0.5},
{xPack, 0, 0.5},
{xPack, 0, 1.5},
{xPack2, 0, 0},
{xPack2, 0, 1},
}
local layer2 = {
{layer2offsetx - xPack, yPack, 0},
{layer2offsetx - xPack, yPack, 1},
{layer2offsetx, yPack, -0.5},
{layer2offsetx, yPack, 0.5},
{layer2offsetx, yPack, 1.5},
{layer2offsetx + xPack, yPack, 0},
{layer2offsetx + xPack, yPack, 1},
{layer2offsetx + xPack2, yPack, -0.5},
{layer2offsetx + xPack2, yPack, 0.5},
{layer2offsetx + xPack2, yPack, 1.5},
}
local layer3 = {
{layer3offsetx - xPack, yPack2, -0.5},
{layer3offsetx - xPack, yPack2, 0.5},
{layer3offsetx - xPack, yPack2, 1.5},
{layer3offsetx, yPack2, 0},
{layer3offsetx, yPack2, 1},
{layer3offsetx + xPack, yPack2, -0.5},
{layer3offsetx + xPack, yPack2, 0.5},
{layer3offsetx + xPack, yPack2, 1.5},
{layer3offsetx + xPack2, yPack2, 0},
{layer3offsetx + xPack2, yPack2, 1},
}
local layer4 = {
{0, yPack3, 0},
{0, yPack3, 1},
{xPack, yPack3, -0.5},
{xPack, yPack3, 0.5},
{xPack, yPack3, 1.5},
{xPack2, yPack3, 0},
{xPack2, yPack3, 1},
}
local layers = {
{y = layer1[1][2], points = layer1}, -- layer1[1][2] is the y value of the first point in layer1, and all spheres in a layer have the same y
{y = layer2[1][2], points = layer2},
{y = layer3[1][2], points = layer3},
{y = layer4[1][2], points = layer4},
}
-- Geode mapgen functions (AKA proof of secondary/spare region concept)
-- fast for small lists
function insertionSort(array)
local i
for i = 2, #array do
local key = array[i]
local j = i - 1
while j > 0 and array[j] > key do
array[j + 1] = array[j]
j = j - 1
end
array[j + 1] = key
end
return array
end
local distSquaredList = {}
local adj_x = 0
local adj_y = 0
local adj_z = 0
local lasty, lastz
local warpx, warpz
-- It's quite a lot to calculate for each air node, but its not terribly slow and
-- it'll be pretty darn rare for chunks in the secondary region to ever get emerged.
mapgen.getGeodeInteriorNodeId = function(x, y, z)
if z ~= lastz then
lastz = z
-- Calculate structure warping
-- To avoid calculating this for each node there's no warping as you look along the x axis :(
adj_y = math.sin(math_pi / 222 * y) * 30
if y ~= lasty then
lasty = y
warpx = math.sin(math_pi / 100 * y) * 10
warpz = math.sin(math_pi / 43 * y) * 15
end
local twistRadians = math_pi / 73 * y
local sinTwist, cosTwist = math.sin(twistRadians), math.cos(twistRadians)
adj_x = cosTwist * warpx - sinTwist * warpz
adj_z = sinTwist * warpx + cosTwist * warpz
end
-- convert x, y, z into a position in the tessellating space
local cell_x = (((x + adj_x) / xPack2 + 0.5) % structureSize) / structureSize * xPack2
local cell_y = (((y + adj_y) / yPack3 + 0.5) % structureSize) / structureSize * yPack3
local cell_z = (((z + adj_z) + 0.5) % structureSize) / structureSize -- zPack = 1, so can be omitted
local iOut = 1
local i, j
local canSkip = false
for i = 1, #layers do
local layer = layers[i]
local dy = cell_y - layer.y
if dy > -0.71 and dy < 0.71 then -- optimization - don't include points to far away to make a difference. (0.71 comes from sin(45°))
local points = layer.points
for j = 1, #points do
local point = points[j]
local dx = cell_x - point[1]
local dz = cell_z - point[3]
local distSquared = dx*dx + dy*dy + dz*dz
if distSquared < 0.25 then
-- optimization - point is inside a sphere, so cannot be a wall edge. (0.25 comes from radius of 0.5 squared)
return c_air
end
distSquaredList[iOut] = distSquared
iOut = iOut + 1
end
end
end
-- clear the rest of the array instead of creating a new one to hopefully reduce luajit mem leaks.
while distSquaredList[iOut] ~= nil do
rawset(distSquaredList, iOut, nil)
iOut = iOut + 1
end
insertionSort(distSquaredList)
local d3_1 = distSquaredList[3] - distSquaredList[1]
local d3_2 = distSquaredList[3] - distSquaredList[2]
--local d4_1 = distSquaredList[4] - distSquaredList[1]
--local d4_3 = distSquaredList[4] - distSquaredList[3]
-- Some shape formulas (tuned for a structureSize of 50)
-- (d3_1 < 0.05) gives connective lines
-- (d3_1 < 0.05 or d3_2 < .02) give fancy elven bridges - prob doesn't need the d3_1 part
-- ((d3_1 < 0.05 or d3_2 < .02) and distSquaredList[1] > .3) tapers the fancy connections in the middle
-- (d4_3 < 0.03 and d3_2 < 0.03) produces caltrops at intersections
-- (d4_1 < 0.1) produces spherish balls at intersections
-- The idea is voronoi based - edges in a voronoi diagram are where each nearby point is at equal distance.
-- In this case we use squared distances to avoid calculating square roots.
if (d3_1 < 0.05 or d3_2 < .02) and distSquaredList[1] > .3 then
return c_crystal
elseif (distSquaredList[4] - distSquaredList[1]) < 0.08 then
return c_glowstone
else
return c_air
end
end