Info en anglais sur l' IA
Hey people,
If you remember about a month ago the Russian games magazine PC Games ran a STALKER Developer Diary in their 10th issue. You can read our translation of that HERE. Issue 11 of PC Games is now out, as is part 2 of the dev diary.
Is there life in The Zone?
Translated by: Oblivion-Lost.com
Original Source
The artificial intelligence in STALKER allows both people and animals to weight up their chances for survival and act accordingly. You won't often see a stalker with a pistol try to take on a soldier armed with an assault rifle. Of course, rare exceptions are possible, but these will come about because of the unhealthy psycological state of the stalker. We introduced the concept of a "fair intelligence". In general, the NPCs in FPS games know exactly where the player is, because this is known to the God-like all-knowing AI controlling them. In STALKER the enemy AI can only "assume" where the player is. The AI remembers the last spot where it saw the player, and tries to find him using the "what would I do in his place?" method, i.e. the AI searches for the player by assuming what his next possible position could be. It is often fascinating to observe, after secretly climbing up to the loft of a rural farmhouse, how the enemy stalker carefully circles the building with his AK47 at the ready, trying to figure out where the hell you could've gone.
While creating the combat intellect, we took as our basis the behaviour of a real person, understanding that the AI-controlled NPC must imitate appropriate reactions based on the given situation. During combat, the AI uses all available cover in a realistic way, knowing which surfaces can be shot through and which can't. When it becomes necessary to reload, NPCs retreat behind cover before changing out, returning only once they're ready to fight again. NPCs backpedal, use corners for cover, enter buildings to attain a better firing position, as well as many other fascinating things.
Of course, given the complexity of such AI, we had our share of problems and general weirdness. During early development and testing of combat intelligence, one stalker went mad and began to consider himself as an enemy, trying to dispose of this "enemy" as quickly as possible. Unfortunately, our good-for-nothing animators did not plan for the possibility of putting your own gun to your temple, so the poor stalker had to instead shoot the only part of the "enemy" body he could reach - his own feet. For a good 10 minutes the entire design team, while rolling around on the floor from laughter, watched as the stalker-wannabie desparately battled with his own limbs. In the end, having used up two full magazines, the NPC died, submitting the diagnostic "Enemy successfully terminated" before terminating.
The Zone is saturated with all kinds of information. Just like in the real world, it is absolutely necessary to survive. A timely warning about a pack of blind dogs seen in the area, radioed in by a friendly stalker, can save you a lot of ammunition, and maybe even your life. Rumours of an unknown construction site to the west may drive the player (or NPC stalkers) to move deeper into The Zone. We are not limiting ourselves just to information available to the player, information about the central storyline or possible quests, either. In STALKER, you will have to pick out valuable information from a torrent of everyday facts, just like you do in real life. The Zone is continually filled with rumours. You could find out about a recent battle between two stalker clans, about an accident involving an experienced stalker, about the sudden appearance of an anomalous "hot" zone, about a recently discovered artifact treasure trove in a destroyed physics lab, etc etc. The actions of the player, as well as those of NPC stalkers, could also become the stuff of legend - it is on their basis that the player alignment and standing among the various groups in formed.
Life without mankind
Now's the perfect time to tell you guys all about the most complicated and important part of the Life Simulation System - the complete autonomy of it.
As we mentioned earlier, The Zone is a single large area, and movement within is not limited in any way other than by environmental conditions (i.e. level of radiation the player can currently withstand etc). This "open world" concept is certainly not new, but the game world always "came to life" only when the player was in the immediate vicinity. The critical difference with STALKER is that life within The Zone never stops or slows down, even if the player is in an area many kilometres away. Graphically, The Zone and everything in it is only drawn in the area around the player, i.e. within a certain radius of the player's position. BUT, once outside this radius, an NPC or monster does not just magically disappear into thin air, but rather continue to live and act just as before, although now in a somewhat simplified, purely mathematical world. Here, events happen just as they do around the player: stalkers meet, trade, battle and go on quests, monsters migrate in search of food, sleep, and fight. Any and all events leave their mark on the world. It is perfectly possible to come upon the body of a stalker killed by a rival group, or see the aftermath of a battle between a stalker party and a monster horde. You could find the weapon and equipment dropped by a stalker killed and eaten by a pack of blind dogs. It is even possible to hear rumours about such an event in the bar, and then come to investigate the area, possibly finding a little something for yourself in the process. All dropped objects remain on the ground until someone picks them up or moves them, so it will be perfectly feasible to create a personal stash anywhere in The Zone and use it to store extra equipment etc.
The NPCs are no longer "bots" as we've come to understand them. Inside the game world, they are people, who differ from you only in that their intelligence is artificial. In fact, this is probably the player's only advantage, although even now we continue work to make sure the odds are as evenly matched as possible. This does NOT mean that the NPCs will all be super-accurate shooters and move around like they've got jet packs attached - they miss just like real people, and move just as the player does - we're simply trying to infuse them with a bit of human thinking and unpredictability. Every NPC has their own name and story, you could for example meet a stalker just after he enters The Zone for the first time as a green newbie, and after a while hear about his successes and failures through rumours. Because of this unique approach to AI, NPCs are no longer "non-player" characters, but rather appear to be independent living people.
The Adventures of "Gosha"
Ed. Note: 'Gosha' is a kind of silly Russian name, generally taken to mean the person is not very smart or strong etc. An english equivalent, depending on where you're from I suppose , would be 'Kurtis' or 'Jimmy'.
The Life Simulation System, the heart of the unique game world of The Zone, took us a good 1.5-2 years to create. Throughout this time, our enthusiasm exceeded our skeptisism over the whole thing, however there was a period when we started building a "safety net" as it were, a variant we planned to use if we were unable to create the planned Life Simulation System. This far simpler alternative system was to be rather linear gameplay with strict storyline progression and quests following the good 'ol "Fedex" concept, i.e. "go there, get this, come back here". Still, in the end all that development time on the proper Life Simulation System was not for nothing: all the things we constantly argued about almost to the point of fights in the office slowly began to work properly, and we started to forget the hundreds of times each of us shouted "Mother#^*@&@#$, it @#^*@#* doesn't work!!!" during the last couple of years.
In order to test some of the simulation system elements we built a special level, which was just a huge field covering several kilometers square. The testing basically consisted of dumping a whole zoo of monsters and stalkers onto this field, and the entire development team sitting by the screen and watching what will happen. In order to give the whole thing at least the illusion of a proper test, the game output gameplay statistics onto a second screen at the same time, which mainly looked something like this:
Evnt119: Stalker 'Gosha' #84 was bitten to death by pigs
Evnt120: Stalker 'Gosha' #132 shot and killed a dog (I don't think Greepeace would've liked our testing sessions )
Evnt121: Stalker 'Gosha' #43 picked up the assault rifle belonging to 'Gosha' #84, and is now standing around with two assault rifles like a god damn fool
Evnt122: Stalker 'Gosha' #7 stomped on several rats
Evnt123: The dead rats' mates celebrated by feasting on a dead pig
Evnt124: The pigs didn't like that and wasted 'Gosha' #43
Evnt125: Stalker 'Gosha' #61 is standing over 2 assault rifles scratching his head, because he doesn't know which is better, and cannot use both like 'Gosha' #43 for religious reasons
Evnt126: Stalker 'Gosha' #17, however, is not a religious man
Evnt127: Stalker 'Gosha' #17 killed 'Gosha' #61
Evnt128: Stalker 'Gosha' #17 picked up everything on the ground, including a grenade dropped by 'Gosha' #94, killed earlier by 'Gosha' #84
...
The level was restarted many times, which allowed us to figure out that similar "mad" situations ensued roughly 10-15 times out of every 100. We had instances when a single assault rifle changed hands over 20 times during one round. The Life Simulation System worked, thank god, and we all celebrated our good luck. The problems, however, most certainly did not end there...
TO BE CONTINUED...
Translated by: Spetsnaz
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-= Fight =-