Add Mesh & Face classes for #59

Together, these classes provide a way to represent a mesh of faces
generated from the Minetest world. This way, the generation of a mesh
can be abstracted away from any potential output file writers, thereby
allowing for multiple different output file formats to be supported.

worldeditadditions/init.lua

@@ -9,6 +9,7 @@ worldeditadditions = {}
 worldeditadditions.modpath = minetest.get_modpath("worldeditadditions")
 dofile(worldeditadditions.modpath.."/utils/vector.lua")
 dofile(worldeditadditions.modpath.."/utils/vector3.lua")
+dofile(worldeditadditions.modpath.."/utils/mesh.lua")
 
 dofile(worldeditadditions.modpath.."/utils/strings/init.lua")
 dofile(worldeditadditions.modpath.."/utils/format/init.lua")

worldeditadditions/utils/mesh.lua

@@ -0,0 +1,99 @@
+local wea = worldeditadditions
+
+
+-- ███████  █████   ██████ ███████
+-- ██      ██   ██ ██      ██
+-- █████   ███████ ██      █████
+-- ██      ██   ██ ██      ██
+-- ██      ██   ██  ██████ ███████
+
+--- A single face of a Mesh.
+local Face = {}
+Face.__index = Face
+
+--- Creates a new face from a list of vertices.
+-- The list of vertices should be anti-clockwise.
+-- @param	vertices	Vector3[]	A list of Vector3 vertices that define the face.
+function Face.new(vertices)
+	local result = { vertices = vertices }
+	setmetatable(result, Face)
+	return result
+end
+
+--- Determines whether this face is equal to another face or not.
+-- @param	a	Face	The first face to compare.
+-- @param	b	Face	The second face to compare.
+-- @returns	bool		Whether the 2 faces are equal or not.
+function Face.equal(a, b)
+	if #a.vertices ~= #b.vertices then return false end
+	for i,vertex in ipairs(a) do
+		if vertex ~= b.vertices[i] then return false end
+	end
+	return true
+end
+function Face.__eq(a, b) return Face.equal(a, b) end
+
+
+-- ███    ███ ███████ ███████ ██   ██
+-- ████  ████ ██      ██      ██   ██
+-- ██ ████ ██ █████   ███████ ███████
+-- ██  ██  ██ ██           ██ ██   ██
+-- ██      ██ ███████ ███████ ██   ██
+
+--- A mesh of faces.
+local Mesh = {}
+Mesh.__index = Mesh
+
+--- Creates a new empty mesh object container.
+-- @returns	Mesh
+function Mesh.new()
+	local result = { faces = {} }
+	setmetatable(result, Mesh)
+end
+
+--- Adds a face to this mesh.
+-- @param	self	Mesh	The mesh instance to operate on.
+-- @param	face	Face	The face to add.
+-- @returns	void
+function Mesh.add_face(self, face)
+	table.insert(self.faces, face)
+end
+
+--- Deduplicate the list of faces in this Mesh.
+-- Removes all faces that are exactly equal to one another. This reduces the
+-- filesize.
+-- @returns	number	The number of faces removed.
+function Mesh.dedupe(self)
+	-- Find the faces to remove
+	local toremove = {}
+	for i,face_check in ipairs(self.faces) do
+		for j,face_next in ipairs(self.faces) do
+			if i ~= j	-- If we're not comparing a face to itself...
+				and face_check == face_next -- ....and the 2 faces are equal....
+				and not wea.table_contains(toremove, j) then -- ...and we haven't already marked it for removal...
+				-- Mark it for removal
+				table.insert(toremove, j)
+			end
+		end
+	end
+	-- Sort the list of indexes marked for removal from largest to smallest
+	-- This way, removing smaller items doesn't alter the index of larger ones
+	table.sort(toremove, function(a, b) return a > b end)
+	
+	-- Remove the faces marked for removal
+	for i, remove_index in ipairs(toremove) do
+		table.remove(self.faces, remove_index)
+	end
+	return #toremove
+end
+
+
+if worldeditadditions then
+	worldeditadditions.Face = Face
+	worldeditadditions.Mesh = Mesh
+else
+	return {
+		Face = Face,
+		Mesh = Mesh
+	}
+end

worldeditadditions/utils/tables/init.lua

@@ -20,3 +20,4 @@ dofile(worldeditadditions.modpath.."/utils/tables/table_map.lua")
 dofile(worldeditadditions.modpath.."/utils/tables/table_tostring.lua")
 dofile(worldeditadditions.modpath.."/utils/tables/table_unique.lua")
 dofile(worldeditadditions.modpath.."/utils/tables/table_unpack.lua")
+dofile(worldeditadditions.modpath.."/utils/tables/table_contains.lua")

worldeditadditions/utils/tables/table_contains.lua

@@ -0,0 +1,18 @@
+
+--- Looks to see whether a given table contains a given value.
+-- @param	tbl		table	The table to look in.
+-- @param	target	any		The target to look for.
+-- @returns	bool	Whether the table contains the given target or not.
+local function table_contains(tbl, target)
+	for key, value in ipairs(tbl) do
+		if value == target then return true end
+	end
+	return false
+end
+
+
+if worldeditadditions then
+	worldeditadditions.table_contains = table_contains
+else
+	return table_contains
+end

worldeditadditions/utils/vector3.lua

@@ -1,3 +1,4 @@
+--- A 3-dimensional vector.
 local Vector3 = {}
 Vector3.__index = Vector3