The first version of AI I wrote for the zombies in Survius was more of a prototype for testing purposes. It was really simple, yet effective. However, it needed an overhaul and so I wrote a brand spanking new AI script.
The new AI gives the zombies two ways to track you.
Before anything, a zombie has to see you. When he does, he will try moving directly towards you. He will continue to do so while he has a visual on you.
When you run out of their sight, behind a wall or inside a building, they switch from sight mode to smell mode. They will rely on their smell and will follow your trail until they have a visual on you again, or you run out of their range.
This means the zombies will close in on you directly in an open field. But they will also follow you around objects or inside houses, moving around the furniture. This makes the improved zombies a lot harder to escape.
I've uploaded a video to demonstrate the new AI.