People, they don't mean 'you see 6000 zombies', obviously. They mean that there are 6000 being rendered in the area you're in.

Should be epic.

I think most people realise that , but would it be worth rendering 6000 zombies at a time if only 1500-2000 were visible at any one time ... i'm not even sure it would be possible to fit as many as a 1000 zombies on screen.

If it's like stickball said and it's from a rooftop or something then it's likely the Zombies won't be interactive but procedural.

1500 of them on each side would certainly scare the daylights out of me  

If I remember right, you could throw a propane tank down into the ones outside. They were "real".

That said, 6000 being rendered in any given area is necesarry if this is really going to be multiplayer-- maybe not couch side co-op, but actual multiplayer-- as people coudl be running around all over, and you don't want zombie pop-up.

Using "real" is right here, but why you're using it isn't right.

It's "real" in the sense that you probably can throw something into a sea of zombies you can't really interact with and "kill" them but it isn't "real" in that you can run up to them and hit them with a sword.

As I said, I would be willing to be if there are 6000 zombies on screen then those are all zombies that are far away that you will never be able to touch and have ridiculously low textures and poly's.  They're "real" in the sense you can throw a propane tank out there and trigger an event that makes zombie gibs appear and the zombies around it disappear but the zombies aren't the same ones you interact with.

And don't get me wrong, having 6000 of anything on screen doing something is significant, just don't assume it's 6000 you can actually interact with.

 This I hope for. That would be cool.

It's really not that big of a deal.  Having different AI for them would be a big deal.  There was a simulation with over 15,000 objects (chickens) with their own A.I. on the Cell (page 5).  Without individual A.I. (i.e. minimal crowd A.I.), MLB 09:The Show has around 50,000 people in the stadium stands moving around.

Anyone who is going to count if it are really 6.000 zombies on the screen?

April fools?

But did you read the whole sentence?

"In fact, when the number of chickens was increased to a total of 15,000 birds the Cell B./E. processor was still able to perform the simulation with interactive speed, but the graphics rendering was not able to keep pace, even on a state-of-the-art NVidia GPU and started dropping 2 out of 3 frames, resulting in 10fps "sluggish" video output."