Entities that can't be picked, don't write to the texture, entities that can be picked, write to the texture their id. Whatever is closer to the camera will be the id that stays there (same as a color pixel, but instead of the object color you can think object id).
So you are limited at one ID per pixel, but for me that works.
I played lots of quake2-3 but that wasn't the golden age. Now you have even better selection for competitive gaming, like CS Go, valorant with their 128 ticks/s servers.
It was so hard for him to act like an adult and be considerate about the way he speaks. Such a tragedy requiring immense sacrifice from this poor soul.