function decode_obj(data)

    local vertices = {}
    local normals = {}
    local uvs = {}

    local function insert_triangle(output, indexes)
        local triangle = {}

        local vertex_i, uv_i, normal_i = indexes:match("(%d+)/(%d+)/(%d+)")

        vertex_i = tonumber(vertex_i)
        uv_i = tonumber(uv_i)
        normal_i = tonumber(normal_i)

        if vertex_i then
            triangle.pos = vertices[vertex_i]
        end

        if uv_i then
            triangle.uv = uvs[uv_i]
        end

        if normal_i then
            triangle.normal = normals[normal_i]
        end

        table.insert(output, triangle)
    end

    -- get all the types
    for type, x, y, z in data:gmatch("(.-)%s+(.-)%s+(.-)%s+(.-)\n") do
        if type == "v" then
            table.insert(vertices, Vec3(tonumber(x),tonumber(y),tonumber(z)))
        end

        if type == "vn" then
            table.insert(normals, Vec3(tonumber(x),tonumber(y),tonumber(z)))
        end

        if type == "vt" then
            table.insert(uvs, Vec2(tonumber(x),tonumber(y)))
        end
    end

    local output = {}

    -- assemble them
    for type, a, b, c, d in data:gmatch("(.-)%s+(.-)%s+(.-)%s+(.-)\n") do
        if type == "f" then
            if a and b and c then
                insert_triangle(output, a)
                insert_triangle(output, c)
                insert_triangle(output, b)
            elseif a and b and c and d then
                error("quad is not implemented!", 2)
            end
        end
    end

    return output
end