objloader.lua

local path = ... .. "."
local loader = {}

loader.version = "0.0.2"

function loader.load(path, filename)
	loader.object = {
		v	= {}, -- List of vertices - x, y, z, [w]=1.0
		vt	= {}, -- Texture coordinates - u, v, [w]=0
		vn	= {}, -- Normals - x, y, z
		vp	= {}, -- Parameter space vertices - u, [v], [w]
		f	= {}, -- Faces
		materials = {}
	}

	assert(file_exists(path .. "/" .. filename), "File not found: " .. path .. "/" .. filename)

	local get_lines

	if love then
		get_lines = love.filesystem.lines
	else
		get_lines = io.lines
	end

	local lines = {}

	for line in get_lines(path .. "/" .. filename) do 
		table.insert(lines, line)
	end

	loader.parse(path, filename, lines)

	return loader.object
end

function loader.parse(path, filename, lines)
	for _, line in ipairs(lines) do
		local l = string_split(line, "%s+")
		if l[1] == "mtllib" then
			local mtllibfilename = l[2]
			loader.parseMaterial(path, mtllibfilename)
		elseif l[1] == "v" then
			local v = {
				x = tonumber(l[2]),
				y = tonumber(l[3]),
				z = tonumber(l[4]),
				w = tonumber(l[5]) or 1.0
			}
			table.insert(loader.object.v, v)
		elseif l[1] == "vt" then
			local vt = {
				u = tonumber(l[2]),
				v = tonumber(l[3]),
				w = tonumber(l[4]) or 0
			}
			table.insert(loader.object.vt, vt)
		elseif l[1] == "vn" then
			local vn = {
				x = tonumber(l[2]),
				y = tonumber(l[3]),
				z = tonumber(l[4]),
			}
			table.insert(loader.object.vn, vn)
		elseif l[1] == "vp" then
			local vp = {
				u = tonumber(l[2]),
				v = tonumber(l[3]),
				w = tonumber(l[4]),
			}
			table.insert(loader.object.vp, vp)
		elseif l[1] == "f" then
			local f = {}

			for i=2, #l do
				local line = string.gsub(l[i], "//", "/")
				local split = string_split(line, "/")
				local v = {}

				if #split == 1 then
					v.v = tonumber(split[1])
				elseif #split == 2 then
					v.v = tonumber(split[1])
					v.vn = tonumber(split[2])
				elseif #split == 3 then
					v.v = tonumber(split[1])
					v.vt = tonumber(split[2])
					v.vn = tonumber(split[3])
				end


				table.insert(f, v)
			end

			table.insert(loader.object.f, f)
		end
	end
end

function loader.parseMaterial(path, mtllibfilename)
	assert(file_exists(path .. "/" .. mtllibfilename), "File not found: " .. path .. "/" .. mtllibfilename)

	local lines = {}
	for line in love.filesystem.lines(path .. "/" .. mtllibfilename) do 
		table.insert(lines, line)
	end

	local materials = {}
	local currentMaterialIndex = 0
	for k,v in pairs(lines) do
		local parts = string_split(v, "%s+")
		if parts[1] == "newmtl" then
			currentMaterialIndex = currentMaterialIndex + 1
			materials[currentMaterialIndex] = {
				Name = parts[2]
			}
		elseif parts[1] == "Ka" then
			materials[currentMaterialIndex].Ambient = {
				R = tonumber(parts[2]),
				G = tonumber(parts[3]),
				B = tonumber(parts[4])
			}
		elseif parts[1] == "Kd" then
			materials[currentMaterialIndex].Diffuse = {
				R = tonumber(parts[2]),
				G = tonumber(parts[3]),
				B = tonumber(parts[4])
			}
		elseif parts[1] == "Ks" then
			materials[currentMaterialIndex].Specular = {
				R = tonumber(parts[2]),
				G = tonumber(parts[3]),
				B = tonumber(parts[4])
			}
		elseif parts[1] == "Ns" then
			materials[currentMaterialIndex].Shininess = tonumber(parts[2])
		elseif parts[1] == "map_Kd" then
			materials[currentMaterialIndex].DiffuseTexture = path .. "/" .. parts[2]
		end	
	end

	loader.object.materials = materials
end

function file_exists(file)
	if love then return love.filesystem.exists(file) end

	local f = io.open(file, "r")
	if f then f:close() end
	return f ~= nil
end

-- http://wiki.interfaceware.com/534.html
function string_split(s, d)
	local t = {}
	local i = 0
	local f
	local match = '(.-)' .. d .. '()'
	
	if string.find(s, d) == nil then
		return {s}
	end
	
	for sub, j in string.gmatch(s, match) do
		i = i + 1
		t[i] = sub
		f = j
	end
	
	if i ~= 0 then
		t[i+1] = string.sub(s, f)
	end
	
	return t
end

return loader