factorio/data/core/lualib/resource-autoplace.lua

local noise = require("noise")
local expression_to_ascii_math = require("noise.expression-to-ascii-math")
local tne = noise.to_noise_expression
local litexp = noise.literal_expression

local function get_patch_metaset_patch_set_index(patch_metaset, patch_set_name)
  if patch_metaset.patch_set_indexes[patch_set_name] == nil then
    patch_metaset.patch_set_indexes[patch_set_name] = patch_metaset.next_patch_set_index
    patch_metaset.next_patch_set_index = patch_metaset.next_patch_set_index + 1
    data.raw["noise-expression"][patch_metaset.count_expression_name].expression = tne(patch_metaset.next_patch_set_index)
  end
  return patch_metaset.patch_set_indexes[patch_set_name]
end

local function new_patch_metaset(params)
  data.raw["noise-expression"][params.count_expression_name] =
  {
    type = "noise-expression",
    name = params.count_expression_name,
    expression = tne(0)
  }

  return
  {
    count_expression_name = params.count_expression_name,
    next_patch_set_index = 0,
    patch_set_indexes = {},
    get_patch_set_index = get_patch_metaset_patch_set_index
  }
end

-- This has to be global so that all calls into this library
-- use the same object and get unique patchset indexes.
-- It is not indended to be used directly from outside of this library.
if not resource_autoplace__patch_metasets then
  resource_autoplace__patch_metasets =
  {
    regular = new_patch_metaset{ count_expression_name = "regular-resource-patch-set-count" },
    starting = new_patch_metaset{ count_expression_name = "starting-resource-patch-set-count" }
  }
end

local regular_patch_metaset = resource_autoplace__patch_metasets.regular
local starting_patch_metaset = resource_autoplace__patch_metasets.starting

-- Indicate that a patch set exists and optionally that it also needs a separate starting patch set.
-- Call this to initialize patch sets' indexes in a more deterministic order
-- (see resources.lua for an example) before calling resource_autoplace_settings.
local function initialize_patch_set(patch_set_name, has_starting_area_placement)
  regular_patch_metaset:get_patch_set_index(patch_set_name)
  if has_starting_area_placement then
    starting_patch_metaset:get_patch_set_index(patch_set_name)
  end
end

local pointillist_mode = false
local patch_blobbiness_enabled = true

local function dump_expression(name, expr)
  log(name..":\n"..tostring(expression_to_ascii_math(expr)))
end

local onethird = tne(1)/3 -- Looks nicer in output than 0.333333

--- Creates and returns an AutoplaceSpecification that will generate spot-based ore patches.
-- Required parameters:
-- - name - name for the type, used as the default autoplace control name and patch set name
--   (each of which can be overridden separately)
-- - base_density - amount of stuff, on average, to be placed per tile
-- Optional parameters:
-- - patch_set_name - name of the patch set; patches sets of the same name and seed1 will overlap; default: name
-- - autoplace_control_name - name of the corresponding autoplace control; default: name
-- - random_probability - probability of placement at any given tile within a patch; default: 1
-- - base_spots_per_km2 - number of patches per square kilometer near the starting area
-- - has_starting_area_placement - true|false|nil - yes, no, and there is no special starting area, respectively
-- - seed1 - random seed to use when generating patch positions; default: 100
-- More obscure parameters can be read about in the inline comments.
local function resource_autoplace_settings(params)
  local name = params.name
  local order = params.order or "d"

  local patch_set_name = params.patch_set_name or name
  local autoplace_control_name = params.autoplace_control_name or name

  -- How much of this stuff (probability * richness) should occur per tile on average near the starting area?
  local base_density = params.base_density
  -- Random probability that this stuff is placed when probability is otherwise positive
  -- This IS automatically compensated for by richness, so you don't need to adjust base_density
  local random_probability = params.random_probability or 1
  local base_spots_per_km2 = params.base_spots_per_km2 or 2.5
  local random_spot_size_minimum = params.random_spot_size_minimum or 0.25
  local random_spot_size_maximum = params.random_spot_size_maximum or 2.00
  -- Amplitude of spot 'blob noise' relative to typical spot amplitude
  local regular_blob_amplitude_multiplier = 1/8 * (params.regular_blob_amplitude_multiplier or 1)
  local starting_blob_amplitude_multiplier = 1/8 * (params.starting_blob_amplitude_multiplier or 1)

  local control_setting = noise.get_control_setting(autoplace_control_name)
  local frequency_multiplier = control_setting.frequency_multiplier
  local size_multiplier = control_setting.size_multiplier
  local density_multiplier = frequency_multiplier * size_multiplier

  -- The following are more dangerous, since they'll throw total quantities off if you don't compensate for them:

  -- additional_richness will be added to richness but does not affect probability of anything being placed at all.
  -- This is NOT automatically compensated for, because that would be difficult to calculate.
  -- The caller will need to compensate for any additional_richness by adjusting base_density.
  local additional_richness = params.additional_richness or 0
   -- richness will be clamped to minimum_richness at the low end anywhere the stuff is otherwise placed
   -- Not automatically compensated for.
  local minimum_richness = params.minimum_richness or 0
  -- 'post' as in multiplied after everything else is calculated, including additional_richness
  -- and minimum_richness.
  local richness_post_multiplier = (params.richness_post_multiplier or 1) * control_setting.richness_multiplier

  local seed1 = params.seed1 or 100

  -- rq_factor is the ratio of the radius of a patch to the cube root of its quantity,
  -- i.e. radius of a quantity=1 patch; higher values = fatter, shallower patches
  -- Watch out!  Shallower patches are more heavily thrown off by noise,
  -- so adjust noise amplitude accordingly!
  -- (this is automatically done -- se *_blob_amplitude, below)
  local regular_rq_factor = (params.regular_rq_factor_multiplier or 1) * 1 / 10
  local starting_rq_factor = (params.starting_rq_factor_multiplier or 1) * 1 / 7

  local elevation = noise.var("elevation")
  local distance = noise.var("distance")

  -- > I just realized because of the new rule of "keep ores outside the
  -- > starting area", the starting area size setting should not affect ore
  -- > placement. The ore's starting area should be it's own fixed value
  -- > that ignores the setting.
  -- Twinsen, August 2018
  local starting_resource_placement_radius = 120
  local regular_modulation
  -- has_starting_area_placement values:
  -- - true  - place in starting area and outside starting area independently
  -- - false - place outside starting area but not inside
  -- - nil   - place everywhere as if there is no starting area

  local regular_patch_fade_in_distance = 300
  local regular_ns_multiplier_at
  if params.has_starting_area_placement == nil then
    regular_ns_multiplier_at = function(dist) return 1 end
  else
    regular_ns_multiplier_at = function(dist)
      return noise.clamp((dist - starting_resource_placement_radius) / regular_patch_fade_in_distance, 0, 1)
    end
  end
  local double_density_distance = 1300 -- distance at which patches have twice as much stuff in them

  -- Maximum distance at which blob amplitude should keep increasing along with spot height
  local regular_blob_amplitude_maximum_distance = double_density_distance
  local spot_enlargement_maximum_distance = regular_blob_amplitude_maximum_distance

  -- Get distance for purposes of calculating regular ore density, patch size, and richness
  local function size_effective_distance_at(dist)
    if params.has_starting_area_placement == nil then
      return dist
    else
      -- If there's a starting area measure from the edge of the fade-in radius
      return dist - regular_patch_fade_in_distance
    end
  end

  local function regular_density_at(dist)
    -- Don't increase density beyond spot_enlargement_maximum_distance
    -- because large spots get unwieldy.  We'll increase richness after that, instead.
    effective_distance = noise.clamp(size_effective_distance_at(dist), 0, spot_enlargement_maximum_distance)
    local distance_density_multiplier = 1 + effective_distance / double_density_distance
    return base_density * density_multiplier * distance_density_multiplier * regular_ns_multiplier_at(dist)
  end
  local spots_per_km2_near_start = base_spots_per_km2 * frequency_multiplier
  local candidate_spot_count = params.candidate_spot_count or 21

  if pointillist_mode then
    -- Split ore into lots and lots and lots of little patches
    -- so that we can get a better idea of the underlying distribution
    candidate_spot_count = 10000 -- hardcoded max so we don't melt the player's CPU
    spots_per_km2_near_start = candidate_spot_count
  end

  -- Regular spot quantity without randomization added
  local function regular_spot_quantity_base_at(dist)
    return regular_density_at(dist) * 1000000 / spots_per_km2_near_start
  end
  -- Regular spot quantity averaging over randomization
  local function regular_spot_quantity_typical_at(dist)
    local average_random_size_multiplier = (random_spot_size_minimum + random_spot_size_maximum) / 2
    return average_random_size_multiplier * regular_spot_quantity_base_at(dist)
  end
  local function regular_spot_height_typical_at(dist)
    return regular_spot_quantity_typical_at(dist)^(onethird) / ((math.pi/3) * regular_rq_factor^2)
  end

  local regular_density_expression = regular_density_at(distance)
  local regular_spot_quantity_expression = noise.random_between(random_spot_size_minimum, random_spot_size_maximum) * regular_spot_quantity_base_at(distance)
  local regular_spot_radius_expression = noise.min(32, regular_rq_factor * regular_spot_quantity_expression ^ (onethird))

  if params.has_starting_area_placement ~= nil then
    regular_blob_amplitude_maximum_distance = regular_blob_amplitude_maximum_distance + regular_patch_fade_in_distance
  end
  local function regular_blob_amplitude_at(dist)
    return regular_blob_amplitude_multiplier * noise.min(
      regular_spot_height_typical_at(regular_blob_amplitude_maximum_distance),
      regular_spot_height_typical_at(dist)
    )
  end
  local regular_blob_amplitude_maximum = regular_blob_amplitude_at(regular_blob_amplitude_maximum_distance)
  local regular_blob_amplitude_expression = regular_blob_amplitude_at(distance)

  -- Values for starting spots.
  -- Simpler calculations than for regular spots because they are only placed
  -- in one place and therefore there are fewer variables!

  -- reduce the influence of the frequency slider over the amount of ore in the starting area.
  -- note that starting_spot_count is still set to frequency_multiplier below, so we still split the ore to a fairly high amount of patches.
  local starting_frequency_multiplier = ((frequency_multiplier - 1) * 0.5) + 1
  local starting_amount = 40000 * base_density * starting_frequency_multiplier * size_multiplier
  --local starting_amount = 1000000 -- nicer for testing - just check that all spots have ~1.0M
  local starting_area_sharpness = tne(math.huge)
  local starting_resource_placement_area = math.pi*starting_resource_placement_radius*starting_resource_placement_radius
  local starting_density = starting_amount / starting_resource_placement_area
  -- Goes < 0 outside of starting area and at negative elevations
  local starting_modulation =
    noise.clamp((starting_resource_placement_radius - distance) * starting_area_sharpness, 0, 1)
  local starting_feasibility =
    noise.clamp((elevation - 1) / 10, 0, 1) * starting_modulation
     -- Allow resources at lower elevations for starting

  -- Set minimum_favorability_for_full_placement to lower numbers to decrease the likelihood that the starting patches get split.
  -- Quantity will automatically be clamped by the spot noise function
  -- and radius will be automatically adjusted, too,
  -- so it's fine for the spot quantity to be more than the region target quantity.
  local minimum_favorability_for_full_placement = 1/2
  local starting_spot_count = frequency_multiplier
  local starting_area_spot_quantity = starting_amount / minimum_favorability_for_full_placement / starting_spot_count
  local starting_spot_height = starting_area_spot_quantity ^ (1/3) / ((math.pi/3) * starting_rq_factor^2)
  local starting_blob_amplitude = starting_blob_amplitude_multiplier * starting_spot_height

  -- since starting and regular spots get maxed together,
  -- the basement value should be the lower of the two.
  -- This value needs to be low enough that any noise added to it is still below zero
  -- so that we don't get bits of ores sticking out between spot noise spots.
  -- It also needs to be constant because that's how the spot noise op works.
  -- Simply using -infinity would work, but calculating it based on blob amplitude:
  -- a) looks nicer if you render the value on a map preview
  -- b) acts as a check on our blob_amplitude calculations
  local basement_value = noise.min(-6 * regular_blob_amplitude_maximum,
                                   -6 * starting_blob_amplitude)

  local regular_spots = tne{
    type = "function-application",
    function_name = "spot-noise",
    arguments =
    {
      x = noise.var("x"),
      y = noise.var("y"),
      seed0 = noise.var("map_seed"),
      seed1 = tne(seed1),
      region_size = tne(1024),
      candidate_spot_count = tne(candidate_spot_count),
      suggested_minimum_candidate_point_spacing = tne(45.254833995939045), -- Magic number to match 0.17.50 spot placement, when candidate_point_count was always 128
      skip_span = noise.var("regular-resource-patch-set-count"),
      skip_offset = tne(regular_patch_metaset:get_patch_set_index(patch_set_name)),
      density_expression = litexp(regular_density_expression), -- low-frequency noise evaluate for an entire region
      spot_quantity_expression = litexp(regular_spot_quantity_expression), -- used to figure out where spots go
      hard_region_target_quantity = tne(false), -- it's fine for large spots to push region quantity past the target
      spot_radius_expression = litexp(regular_spot_radius_expression),
      spot_favorability_expression = litexp(1),
      basement_value = basement_value,
      maximum_spot_basement_radius = tne(128)
    }
  }

  -- Don't want to distrurb starting_patch_metaset unless we actually need to.
  local starting_patch_set_index = 0
  if params.has_starting_area_placement == true then
    starting_patch_set_index = tne(starting_patch_metaset:get_patch_set_index(patch_set_name))
  end

  -- If you change starting area region size,
  -- also change the default starting area position in MapGenSettings
  local starting_spots = tne{
    type = "function-application",
    function_name = "spot-noise",
    arguments =
    {
      x = noise.var("x"),
      y = noise.var("y"),
      seed0 = noise.var("map_seed"),
      seed1 = tne(seed1+1),
      skip_span = noise.var("starting-resource-patch-set-count"),
      skip_offset = starting_patch_set_index,
      region_size = tne(starting_resource_placement_radius * 2),
      candidate_spot_count = tne(32),
      minimum_candidate_point_spacing = tne(32),
      density_expression = litexp(starting_density * starting_modulation),
      spot_quantity_expression = litexp(starting_area_spot_quantity),
      hard_region_target_quantity = tne(true), -- Since there's [usually] only one spot, clamp its quantity to the target quantity
      spot_radius_expression = litexp(starting_rq_factor * starting_area_spot_quantity ^ (onethird)),
      spot_favorability_expression = litexp(
        starting_feasibility * 2 -
        1 * distance / starting_resource_placement_radius +
        noise.random(0.5)
      ),
      basement_value = basement_value,
      maximum_spot_basement_radius = tne(128) -- does making this huge make a difference?
    }
  }

  if pointillist_mode or not patch_blobbiness_enabled then
    regular_blob_amplitude_expression = 0
  end
  if not patch_blobbiness_enabled then
    starting_blob_amplitude = 0
  end

  -- Add some blobbiness
  local blobs0 = tne{
    type = "function-application",
    function_name = "factorio-basis-noise",
    arguments =
    {
      x = noise.var("x"),
      y = noise.var("y"),
      seed0 = noise.var("map_seed"),
      seed1 = tne(seed1),
      input_scale = tne(1/8),
      output_scale = tne(1)
    }
  } + tne{
    type = "function-application",
    function_name = "factorio-basis-noise",
    arguments =
    {
      x = noise.var("x"),
      y = noise.var("y"),
      seed0 = noise.var("map_seed"),
      seed1 = tne(seed1),
      input_scale = tne(1/24),
      output_scale = tne(1)
    }
  }
  local blobs0f = blobs0 - 1/4

  local blobs1 = blobs0 + tne{
    type = "function-application",
    function_name = "factorio-basis-noise",
    arguments =
    {
      x = noise.var("x"),
      y = noise.var("y"),
      seed0 = noise.var("map_seed"),
      seed1 = tne(seed1),
      input_scale = tne(1/64),
      output_scale = tne(1.5)
    }
  }
  local blobs1f = blobs1 - onethird -- attempt to remove positive bias

  local regular_patches = regular_spots + blobs1f * regular_blob_amplitude_expression
  local starting_patches = starting_spots + blobs0f * starting_blob_amplitude

  local all_patches
  if params.has_starting_area_placement == true then
    all_patches = noise.max(starting_patches, regular_patches)
  elseif params.has_starting_area_placement == false then
    all_patches = regular_patches
  else -- nil or unspecified means just make it uniform everywhere
    all_patches = regular_patches
  end

  local richness_expression = noise.delimit_procedure(all_patches) -- Re-use all that stuff between richness/probability!
  local probability_expression = noise.clamp(richness_expression, 0, 1)
  if random_probability < 1 then
    richness_expression = richness_expression / random_probability
    probability_expression = probability_expression * tne{
      type = "function-application",
      function_name = "random-penalty",
      arguments =
      {
       source = tne(1),
       x = noise.var("x"),
       y = noise.var("y"),
       amplitude = tne(1/random_probability) -- put random_probability points with probability < 0
      }
    }
  end
  if additional_richness > 0 then
    richness_expression = richness_expression + additional_richness
  end
  if minimum_richness > 0 then
    richness_expression = noise.max(richness_expression, minimum_richness)
  end

  -- sed = size-effective distance
  local function post_semd_richness_distance_multiplier_at(sed)
    local ddd = double_density_distance
    local semd = spot_enlargement_maximum_distance
    -- density = pre-richness-mutliplied density * richness_distance_multiplier.
    -- Since pre-richness-multiplied density plateaus at semd,
    -- richness needs to increase at that point, and by this much:
    return (ddd + sed)/(ddd + semd)
  end
  local richness_distance_multiplier = noise.max(1, post_semd_richness_distance_multiplier_at(size_effective_distance_at(distance)))

  richness_expression = richness_expression * richness_distance_multiplier * richness_post_multiplier

  local ret =
  {
    order = order,
    control = autoplace_control_name,
    probability_expression = probability_expression,
    richness_expression = richness_expression
  }

  return ret
end

return
{
  initialize_patch_set = initialize_patch_set,
  resource_autoplace_settings = resource_autoplace_settings
}