minetest-australopithecus-utils/utils/scatterer.lua

--[[
Copyright (c) 2014, Robert 'Bobby' Zenz
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--- The Scatterer is a (simple) object that allows to scatter objects in
-- a 2D plane.
Scatterer = {}


function Scatterer:new()
	local instance = {
		height = 0,
		items_counter = 0,
		items = {},
		minx = 0,
		miny = 0,
		offset = 0,
		scattered_items = nil,
		source = nil,
		width = 0
	}
	
	setmetatable(instance, self)
	self.__index = self
	
	return instance
end


function Scatterer:check(origin_x, origin_y, item)
	if item.min_distance == nil and item.max_distance == nil then
		return true
	end
	
	local distance = item.min_distance or 0
	if item.max_distance ~= nil then
		distance = math.random(distance, item.max_distance)
	end
	
	for x = origin_x - distance, origin_x + distance, 1 do
		for y = origin_y - distance, origin_y + distance, 1 do
			if x ~= origin_x or y ~= origin_y then
				local index = noiseutil.index2d(x, y, self.width)
			
				if self.scattered_items[index] == item then
					return false
				end
			end
		end
	end
	
	return true
end

function Scatterer:get(x, y)
	x = math.abs(x - self.minx)
	y = math.abs(y - self.miny)
	
	return self.scattered_items[noiseutil.index2d(x, y, self.width) + self.offset]
end

function Scatterer:get_item(x, y, value)
	for idx = 0, self.items_counter - 1, 1 do
		local item = self.items[idx]
		if (item.threshold == nil or value >= item.threshold)
			and (item.probability == nil or self:next_random_probability() <= item.probability)
			and self:check(x, y, item) then
			return item
		end
	end
	
	return nil
end

function Scatterer:init(source, minx, miny, width, height, offset)
	self.source = source
	self.minx = minx or 0
	self.miny = miny or 0
	self.width = width or 112
	self.height = height or 112
	self.offset = offset or 0
	
	self.scattered_items = {}
	
	local max_counter = self.width * self.height - 1
	
	local numbers = {}
	
	for counter = self.offset, max_counter + self.offset, 1 do
		numbers[counter] = counter
	end
	
	for counter = self.offset, max_counter + self.offset, 1 do
		local swap_index = math.random(counter, max_counter + self.offset)
		
		local temp = numbers[counter]
		numbers[counter] = numbers[swap_index]
		numbers[swap_index] = temp
		
		local number = numbers[counter]
		local x = math.fmod(number, self.width)
		local y = math.floor(number / self.width)
		local index = noiseutil.index2d(x, y, self.width)
		local value = 1
		
		if self.source ~= nil then
			value = self.source[index]
		end
		
		self.scattered_items[index] = self:get_item(x, y, value)
	end
end

function Scatterer:next_random_probability()
	return (10000 - math.random(0, 10000)) / 10000
end

function Scatterer:register(item)
	self.items[self.items_counter] = item
	self.items_counter = self.items_counter + 1
end