Rooting a device for the first time is exciting. However, that is unfortunately not where the battle for root typically ends, despite end user wishes. When new OS or bootloader updates are released, root access is often lost. Unfortunately, the push to root the new firmware isn’t always as fervent as on the original ROM.
Luckily this isn’t the case for the LG Optimus 3D, as XDA Member darkoctavius has posted about a method that will root those LG Optimus 3Ds that lost root when they were updated to Gingerbread. Unfortunately, it only works for the V20x firmwares, so if you’re running V21 or later, you may be out of luck for the time being. For those who are on V20x, you simply plug in your phone with charge only and USB Debugging on and run the run.bat file. Because it’s a .bat, that means it’s only compatible with Windows PC at this time.
For more information, the download link and additional information, you can find all that and more in the original thread. As usual, root methods can be pretty dangerous, so be sure you read all the instructions and are doing it right._________