Tactical AI Kit: Pursuit, Close Combat, and Sniping

Hello children!


Woot, more features. Read on or fail.

What to do when there's no cover
My AI system functions well in a close-quarters environment, or anywhere with lots of objects to take cover and navigate through. A new map I played with showed me that they don't perform well when there is no cover around. They stop where they are and they will shoot at you on sight.

There was a problem with that. They only shot *on sight*. Meaning, if an enemy is at a far enough distance to the point which they cannot be seen unless moving or firing, we'll see some pretty wacky behavior. If the NPC sees the player running across a field far away, for example, the NPC will stop, crouch, and squeeze off some rounds if there is no cover to do this from. If the player stops moving, they are no longer visible, and the NPC sits there.

My next plan was to add a wander function during their attack procedure. This resulted in the NPC running away aimlessly and shooting insanely in the player's general direction. Hmmm, no. Not quite what I'm looking for.

Yesterday I added a close attack state to the AI code, which defines separate behavior for NPCs who have no nearby cover or who decide that cover is not worth running to. This state is pretty simple now, but will be enhanced as much as I see fit.

There was an article about the Killzone AI that inspired me to work on this state. The close attack state looks at path nodes within a certain radius of the NPC, and then assigns a cost to each one based on preferred attack range, line of sight, and other factors, to see which node is best to attack from. The NPC moves to that node and fires at the enemy.

I incorporated a system like this for the close attack state which does the same thing with the path nodes. When the NPC can't find cover, he should be able to find a location as advantageous as possible to avoid being killed.

The enemy's running away! What ever shall I do?
Chase after him, maybe?

Close attack worked great, until I run and hide. My new test map contains tons of hills and trees to dart around, making it easy to hide in the woods. Wouldn't it be great if the NPC would follow me into the woods to kill me? Yes.
Whenever the NPC sights an enemy, he remembers where he is. That way, once the enemy is out of sight, he can move to the last known position. From there, if he sees the enemy again, he will start attacking again. If we don't see him from there, we can initiate a search from that position. Some pretty epic chases have resulted from this :D

Do I really need to empty my clip on this guy?
Inspired by the attack code in Killer Kork, the close attack state now has support for sniping. If a target is moving slowly enough, is far enough away, and it does not appear to know of the NPC's presence, the NPC will snipe. The view distance will be increased (field-of-view is also decreased), the think rate will be tripled, accuracy will be improved, and the NPC will aim for the target's head.

This is a quick video of the new close attack procedure. I run around a few of my maps with the player set to not receive damage.