My friend is a GTA obsessive fan like how I am for Hitman.
He shared me this video of a youtuber who explained the technical gameplay/animation for upcoming GTA 6 based on 5 technical patients.
It’s in Hindi and there is audio option to change to English.
In short - the npc are going to be more realistic. I personally liked their “Runtime Animation Retargeting” concept (US20250095261A1 - System and method for runtime retargeting - Google Patents). More description in the video.
