Currently, the RPCS3 emulator does not support reading PlayStation 3 game data directly from the disc. PS3 game discs are formatted in a such a way that the majority of disc drives on the market cannot read them. Therefore, you need either a PS3 console or a Blu-ray drive that is capable of reading the disc. Since most PC's do not have a Blu-ray drive that can read PS3 game discs, it is necessary to dump the PS3 game data first, then run that digital copy of the game with the RPCS3 emulator.