1VoxelArea = {
2	MinEdge = {x=1, y=1, z=1},
3	MaxEdge = {x=0, y=0, z=0},
4	ystride = 0,
5	zstride = 0,
6}
7
8function VoxelArea:new(o)
9	o = o or {}
10	setmetatable(o, self)
11	self.__index = self
12
13	local e = o:getExtent()
14	o.ystride = e.x
15	o.zstride = e.x * e.y
16
17	return o
18end
19
20function VoxelArea:getExtent()
21	local MaxEdge, MinEdge = self.MaxEdge, self.MinEdge
22	return {
23		x = MaxEdge.x - MinEdge.x + 1,
24		y = MaxEdge.y - MinEdge.y + 1,
25		z = MaxEdge.z - MinEdge.z + 1,
26	}
27end
28
29function VoxelArea:getVolume()
30	local e = self:getExtent()
31	return e.x * e.y * e.z
32end
33
34function VoxelArea:index(x, y, z)
35	local MinEdge = self.MinEdge
36	local i = (z - MinEdge.z) * self.zstride +
37			  (y - MinEdge.y) * self.ystride +
38			  (x - MinEdge.x) + 1
39	return math.floor(i)
40end
41
42function VoxelArea:indexp(p)
43	local MinEdge = self.MinEdge
44	local i = (p.z - MinEdge.z) * self.zstride +
45			  (p.y - MinEdge.y) * self.ystride +
46			  (p.x - MinEdge.x) + 1
47	return math.floor(i)
48end
49
50function VoxelArea:position(i)
51	local p = {}
52	local MinEdge = self.MinEdge
53
54	i = i - 1
55
56	p.z = math.floor(i / self.zstride) + MinEdge.z
57	i = i % self.zstride
58
59	p.y = math.floor(i / self.ystride) + MinEdge.y
60	i = i % self.ystride
61
62	p.x = math.floor(i) + MinEdge.x
63
64	return p
65end
66
67function VoxelArea:contains(x, y, z)
68	local MaxEdge, MinEdge = self.MaxEdge, self.MinEdge
69	return (x >= MinEdge.x) and (x <= MaxEdge.x) and
70		   (y >= MinEdge.y) and (y <= MaxEdge.y) and
71		   (z >= MinEdge.z) and (z <= MaxEdge.z)
72end
73
74function VoxelArea:containsp(p)
75	local MaxEdge, MinEdge = self.MaxEdge, self.MinEdge
76	return (p.x >= MinEdge.x) and (p.x <= MaxEdge.x) and
77		   (p.y >= MinEdge.y) and (p.y <= MaxEdge.y) and
78		   (p.z >= MinEdge.z) and (p.z <= MaxEdge.z)
79end
80
81function VoxelArea:containsi(i)
82	return (i >= 1) and (i <= self:getVolume())
83end
84
85function VoxelArea:iter(minx, miny, minz, maxx, maxy, maxz)
86	local i = self:index(minx, miny, minz) - 1
87	local xrange = maxx - minx + 1
88	local nextaction = i + 1 + xrange
89
90	local y = 0
91	local yrange = maxy - miny + 1
92	local yreqstride = self.ystride - xrange
93
94	local z = 0
95	local zrange = maxz - minz + 1
96	local multistride = self.zstride - ((yrange - 1) * self.ystride + xrange)
97
98	return function()
99		-- continue i until it needs to jump
100		i = i + 1
101		if i ~= nextaction then
102			return i
103		end
104
105		-- continue y until maxy is exceeded
106		y = y + 1
107		if y ~= yrange then
108			-- set i to index(minx, miny + y, minz + z) - 1
109			i = i + yreqstride
110			nextaction = i + xrange
111			return i
112		end
113
114		-- continue z until maxz is exceeded
115		z = z + 1
116		if z == zrange then
117			-- cuboid finished, return nil
118			return
119		end
120
121		-- set i to index(minx, miny, minz + z) - 1
122		i = i + multistride
123
124		y = 0
125		nextaction = i + xrange
126		return i
127	end
128end
129
130function VoxelArea:iterp(minp, maxp)
131	return self:iter(minp.x, minp.y, minp.z, maxp.x, maxp.y, maxp.z)
132end
133