Saturday, March 13, 2010

A technical and pseudo psychological peek into Raven Shields AI

In putting the last touches on Private Airport (kai), I've been spending some more time to study how the games Artificial Intelligence works, special thanks to [SAS]_Maj_WIZ for pointing out a more thorough list of developer diagnostics ;). Since this is the closest look I've taken at Rainbows AI in about 5 years, and an even closer study of Terrorist and Hostage behaviour, I think it's only fair to make a journal entry about it.

Here is a summery of my findings, and annotations about theories I've maintained for years:

The laser eyebrow problem
From the standing position, the source of each pawns aim is directly behind the skull, roughly where the head would be if the pawns stood erectly (like a tango). The point of aim, passes directly though eye level. When crouched the point is roughly near to behind the collar bone, and passes through the lower nasal cavity. In prone, it is much the same.

In real life (and any decent shooting game), that aim point should be chained to the weapon in the players hands.

How Tangos Fire Out Their Ass
Experiments with ShowFOV and GunDirection, demonstrate that there is no real connection between pawn animations, where the AI is looking, and where the AI is actually aiming; or as I have been saying for years, What You See Is Not Always What You Get. The most humerus moment in my testing, occurred with the Rear Guard "Facing" the rear but covering the elements front. My research shows that even if Rainbow is aiming at the target, they fail to engage terrorists outside their point of view. I.e. in the case of that rear guard, if a tango had walked up behind the element: it would've taken a moment for his aim point to realign with his field of view, resulting in the death of 2/3 the Rainbow AI element!

In short, this means that the AI walks around much like a Tank with an independent turret, only the artificial intelligence is riding in the drivers seat, not the gunners. Coincidentally, this is why the game has no real concept of muzzle clearance (as I have also been saying for years).

This may explain some of the more rolling on the floor laughing moments that often occur, when a "How close can you go" opportunity crops up in game. To prove a point, I cornered a tango in a corner and had him empty his magazine into me. Side stepping away and deactivating GOD mode, he was able to fire several rounds point blank into my pawn, before his aim point rotated to my new position - I died once the aim point got to me, not when the animations showed him shooting me.

Also it seems that hostages always seem to aim directly at Rainbow, but luckily the terrorist AI doesn't notice that (or they would always see us comming).

So far, these tests satisfactory seem to prove that my ~6 years old hypothesis, about the "Tango firing out of his arse" problem being is indeed codified into Raven Shield by design. Between network latency, the (usual) use of unreliable UDP communication methods for multiplayer game play, and the systems divergent means of rendering and applying these actions (seeing, aiming, firing, hitting), suggest that there is no way to solve the aforementioned (annoying) problem without fundamental changes to the way Raven Shield works. Since that is not viable, one can only look at working around the problem; even with more processing power then a Cray XT5 super computer, you also need a very high throughput network link between clients and server, likely to an extend that is unobtainable over the modern internet.

In laymen's terms, this means no matter how good your computer hardware or internet connection is,  the computer will always be able to cheat you. Should that change, most likely it will be so far in the future, we will be dead by then.

On the upside, I do believe that why the game is like this, was probably done in order to give the player more 'time' to shoot first (yes, some tangos have very slow reaction times: this appears why). It also appears to explain many of the discrepancies between common online play, single player, and LAN parties. However it is also worth noting, that this may have instead occurred due to limitations of the Unreal Engine (2) or Raven Shields own design and implementation.

Interesting Note: Now that an illegal RvS 1.60 SDK is available on the internet, it may be possible for cheaters to develop a method to take advantage of these problems. Imagine walking up on some one in Adversarial because you think they are looking away, then they shoot you out their arse ;). Luckily the engine has some respectable counter messures to such becoming (more) common.

Looking at the AIs skills
One of the very few things, that I have ever been able to praise Rainbow Six 3: Raven Shield for, is that the Rainbow AI often "Appears" to be covering their sectors, even if they totally suck at room clearing. In fact, their room clearing behaviour suggests that either the AI engine is extremely limited, or the game was made by people who know as much about CQB as the average RvS player, that is: absolutely nothing.

Since there is no connection (see above) between where the character on screen is looking (seeing), and where they are aiming (pointing), this means What You See Is Really Not What You Get. Have you ever seen in Single Player, where Rainbow is looking straight at a tango and gets owned without a shot? This is why. It is also why we can do the same to tangos online.

Terrorist movement is closer to What You See Is What You Get, then Rainbows; IMHO the movement for Rainbow was done to 'look' more realistic then it actually is (or the AI programmer sucked even worse then everything thinks). They also seem to have a tendency to remain fixed on hostages with their aimpoint, even while walking around a fair distance away. Ever got first sight on a tango, shot him trice, only to curse at him "Magically" shooting the hostage with barely a twitch? Yeah baby... he had that gun pointed at the hostage, all the while he was looking into your eyes.

Every type of AI in the game, demonstrates very poor skills at getting around the maps. I remember when I first started learning about pathing in Unreal Engines, I couldn't help but think, "We're still living in a dark age"... and that's all I will say on that lol.

Hostage behaviour, well, what can I say... what you see is exactly what you get: a stupid slug. On the upside, the terrorists do not show any signs of being aware to hostages; this is why for example, if a Rainbow goes down while escorting, and the hostage becomes a prisoner again, the terrorist may continue walking past. All the fancy stuff about the tangos shooting the hostage, is a mixture of the games rudimentary AI, and things that map designer has programmed.

Since I don't believe in taking advantage of the map design, or exploiting things I shouldn't know in real life about the missions, I will not make a closer study of that kind of stuff, nor will I tell others much about it. If you want to figure out how to take even that (ugly) edge over the game, you can go learn how RvS works for yourself. Beat it punk.

I just study the mechanics and psychology of the games AI, you know, the whole know your enemy thing. In actual ops with SAS, I tend to employ more knowledge of human psychological behaviour then how the game was designed. That is both by intention

A Random Bullet Test
A tango surrendered and I fired a shot into his head, the round should have impacted his hand (placed on his head). There was a blood puff and a bullet hole in the wall directly behind his head, however the tango survived. Weapon used was an M16A2 at approximately 350-450 unreal units.

This suggests that terrorists have no brains, since the angle means the bullet must have penetrated his skull, and his hand (I pray) being all that slowed the high velocity FMJ round down enough to prevent a kill. Suggesting that any hit box modifiers applied, were for a 'hand' (arm) shot rather then a head shot.

N.B. other tests I have done over the years suggest this kind of problem and the ballistics model used, is why sniper rifles may incur a two-shot requirement on tango kills, and the exaggerated effects of JHP/FMJ selection on SWAT 4.

Anyone still awake and scratching their heads?

All this is based on roughly 6+ years of playing the game, much more then trivial knowledge of such matters, and being a very, highly observant individual.

No comments:

Post a Comment