I was using my MBP and all of a sudden all these artifacts, coloured lines etc came across my screen. I think I have the dedicated GPU model. Does it sound like the GPU is dying/died? Are GPUs replaceable?
That sounds like a GPU issue for sure. Beyond that, I don't know. I'd run the Apple Hardware Test, but that may only be available at the apple store. Do you have coverage still? The GPU is *not* replaceable, it would be the full logic board.
OK.. that's not great but I would still book an appointment (if you are able) and take it in. Just be truthful with them, be polite, and don't be demanding or anything, I would not be surprised if they fix it for you.