Faces of War - Enthüllt: Die Geheimnisse der KI!
Ubisoft hat ein Q&A veröffentlicht, die sich mit der künstlichen Intelligenz (KI) von Faces of War beschäftigt. Der gesamte Text ist sehr lang, aber natürlich wollen wir ihn euch nicht vorenthalten. Bislang liegt die Q&A allerdings nur auf Englisch vor, ob und wann es das Ganze auch auf deutsch gibt, ist noch nicht bekannt.
Außerdem wurde ein dreiminütiges Video veröffentlicht, das Spielszenen aus dem Level "Omaha Beach" (D-Day) zeigt und sich mit der Gegner-KI beschäftigt. Saugen könnt ihr das Video in zwei verschiedenen Auflösungen, je nach Internetverbindung.
- Schon gesehen?
1. Please tell us, why you are so proud about the AI in 'Faces of War'.
First of all, AI is the offspring of our long-term work. Second reason, we received at the end a very qualitative and broad abilities of AI. From the very beginning AI in 'Faces of War' was based on use of actual information. AI in 'Faces of War' doesn't cheat. It means that our AI doesn't use the info, which is not available for a unit in reality. To put it simple each unit has "eyes", "ears" and "memory". The units can see and hear. Mainly it has influence on the decisions of AI. However the eyesight and hearing have their limitations, there are usual ones. The enemy can disappear, having hidden behind a structure or a ground fold. Even in this situation the AI would behave adequate. Once noticed the enemy, a soldier can chase it, basing on his memory about the enemy though without seeing it. The units can exchange information about the availability and location of enemy forces. It looks as follows, if a soldier from the enemy squad noticed you, he can sound the alarm and the whole army would attack you. You should give up reckoning to lure the enemy out of the base one by one and kill them quietly. By the way it is quite hard to do it quietly, because the shots will be heard and the attacker will be searched around.
Besides conscious decisions, AI in 'Faces of War' has basic self-preservation instinct. It helps to make the behavior of soldiers more natural. The units can defend differently: they hide, if they are severely injured; they flee from thrown grenades and give way to moving vehicles. In principle this all is natural and the player perceives it in this way. On a battlefield players will see not just dummies, which execute orders and move along the given trajectories.
All the above mentioned is surely important. However we needed something else to create real hostilities in the gaming environment. The soldiers on the battle field don't run singly and don't make decisions on their own, because we created an additional 'level' of soldier thinking - the squad thinking. The decisions are made in the squad not only by the unit individually, but there are also commands of the squad leader. This form of a squad represents a complete military unit, which actions are harmonious and organized.
2. How does the AI in 'Faces of War' differ from AI in a typical RTS? Was it difficult to integrate the AI during the game development?
First of all I'd like to mention that AI in 'Faces of War' can not be called strategic in the direct meaning of this word. It is rather tactical. This difference alone is important. Tactical AI gives the soldiers opportunity to fight tactically. The main factor is not, who has got more soldiers, or how well they are armed. Such factors as terrain features, positions of objects, which soldiers can use as covers also play an important role. These are not scales, which can estimate the number/quality of soldiers and draw a conclusion about the battle outcome. The tactics suggests a lot of parameters, which influence the outcome of each even small battle.
Thus, the whole system of AI is based on "honest" data, just to let the player feel that tactics works naturally. If we had used common principles of AI-design, the player would feel embarrassed. There is no unified Master Brain in our system, which sees and knows everything and sends its units to most profitable places.
Each unit is a separate brain, which has feelings and senses. This brain makes decisions individually and puts them into life. Even if soldiers can tell each other about the enemy, it doesn't mean that their decisions will be similar. It is rather difficult to put it other way, but the AI design of soldiers will allow them to communicate with each other. As a result it looks like rather conscious actions - very realistic.
If we take into consideration the fact that soldiers are able to act in squads, we get a rather realistic view. Groups of soldiers act all together, they shoot, move around the terrain, kill enemies or withdraw fighting, hide in houses or in ruins. With the whole complexity of AI system the behavior of soldiers looks natural and doesn't arouse any admonitions. You can be sure, in 'Faces of War' you'll fight not against scripts and waypoints, but against a thinking enemy, who behaves in appropriate manner.
The development of AI of this level was not a piece of cake. Only in early versions the system was developed using a well-grounded scheme. The majority of developments, which followed afterwards were made with the help of the "cut and try method". We invented a new feature, realized it in a draft version and tested it. In course of time we either deleted this feature or improved it to the state of a final version. Such iterative work allowed us to understand our goal clearly at the each stage of production. However it was required to have the AI as a part of the game, otherwise we'd fail to carry out continuous tests "as they are", i.e. directly in the game.
3. Are there any AI aspects, which are remarkable in your opinion and why?
If you will have a look at the behavior of AI-units, first what attracts your attention is the naturalness of this behavior itself. This is most important what we wanted to receive from our AI. All abilities of AI, its complexity and interconnection could have become just a useless burden, if AI didn't behave naturally. It makes no sense to teach the player to understand AI; there are a lot in the game to master. The situations, when the player acts according to the rules of units controlled by AI, must not occur. In the opposite, the player should acquire its natural playing way and the AI system must correspond with these actions.
The functions, which allow the soldiers not only move, but also fulfill some fighting activities, have been integrated into the game exactly with this purpose. The soldiers were equipped with an ability to withdraw fighting and constantly shooting at the enemy. They can start a massive attack as well. Besides, soldiers don't simply take covers, but they can move from one shelter to another in short runs shooting at the enemy. Here I'd like to answer possible questions; this is not script or pattern behavior of soldiers. This is one of action pattern of soldiers and they can apply it whenever they like.
Another factor, which proves the naturalness of AI-unit behavior, is their morale. In principle soldiers estimate not only possible variants of advancing and other actions, but also they consider the type of enemy. Just like in the real life in 'Faces of War' an average soldier of sound mind would not attack a tank with a sub-machine gun. Soldiers take the number of enemies, its arms, availability of vehicles (its type) into account. The strength of own forces plays also an important role. The summation of these factors suggests a decision for soldier. As a result only the soldiers with anti-tank-defense weapons (most efficient are bazookas) would attack the enemy advancing under support of tanks. When heavy vehicles like tanks are destroyed, other soldiers can attack the remaining infantry.
4. Can you explain, how AI system would serve tactical actions of a player?
It will serve them quite directly. The player will have the whole system of AI at his disposal, which was developed for individual and squad behavior of units. Only the squad commander will stay under direct control of player, most of the time the player must manage the squad control. It means that other squad soldiers rather obey to the orders of the squad commander, than to direct instructions of the player. Such system allows the player to control mostly the commander, knowing that other part of the squad executes the received orders. It considerably simplifies the squad control and the understanding of the situation.
It means, the player gives orders to the commander, the commander gives orders to other squad soldiers and they follow them. They follow also their commander; however don't forget about their individual tasks within the whole squad activity. They automatically acquire their targets and start firing. If required they run to locations from which they can shoot more efficiently. Moreover soldiers throw grenades to the targets hidden from direct fire, if required they change their locations or just approach nearer. Antitank grenade launchers and bazookas are used against vehicles. Soldiers take covers depending on the commander location. If required they start close combat. Each soldier can solve one of his tasks in his own unique way; they are united by the commander, who is controlled by the player. For example, a very useful thing - a fighting offensive, after the order is received, the squad starts attacking the enemy line covering at the same time the attack with fire. Soldiers move in turns and shoot at enemy also in turns, without letting it do the same.
Putting it simply, the player gives general instructions, and the soldiers fulfill small tasks themselves. The player can give precise instructions as well, if he wants. The Direct Control mode is designed for hardcore players, who wish to control their units more precisely. This is pure Direct Control, and it has no features of AI. Everything has its good points.
Besides, AI is purposed not only for direct tactical goals of a player, but it works if the player's control is absent. Soldiers keep fighting further, they keep obeying commander's orders, follow him and try to survive in any possible way. They will not disband, but remain a separate military unit, able to defend oneself, if it is hard. However it is no advisable to abuse the independent actions of a squad, it will not be able to fulfill the whole work instead of the player.
5. Do you have any interesting tactical skills to illustrate the enemy AI?
There are several interesting skills among maneuvers, which the enemy AI can apply against the player. For example if the player attacks the enemy, and it defeats, enemy soldiers can hide somewhere instead of running away. They will hide behind structures, in covers or in other places, the main idea to disappear out of sight. If an AI soldier is seriously injured, first of all he will stay in cover, second he will bandage himself. Sometimes it comes to some kind of an ambush in this way. If the player lost the trace of the enemy, he can order his squad to start searching for it. It can happen that the enemy has partially healed his injuries and took rather nice covers in some house ruins. In this case the player can get under a cross-fire from different points at the same time.
In the opposite, if the player has entrenched himself somewhere and is facing the AI of enemies, they will not attack the defense line plainly, loosing manpower in useless manner. They will attack from flanks of throw grenades from safe points. They will start attacking gradually, carefully, changing covers and giving fire support in turns. Both AIs, the one of the enemy and of the player, are equal in strength. In addition there are some actions, which enemy soldiers fulfill automatically. For example they repair their vehicles themselves. It looks as follows, for example a member of a tank crew takes a repair kit (if it is available) and starts repairing. After it he puts the repair kit back, climbs back to the tank and it moves further.
6. The player in 'Faces of War' will command a squad of six soldiers, which is a complicated task in itself, especially if the whole army depends on you. What does AI allow for the squad in the game?
In 'Faces of War' we developed a sort of a unique control system, which is based on three fundamentals. First one is the Direct Control, which is well-known to the players of 'Soldiers: Heroes of WWII'. This is the lowest, mostly concretized control mode. The next level is the common tactical control, it is familiar from the majority of strategy/tactical games and even from MMORPG, the so-called "point-and-click system". This system is well-known and doesn't deliver any problems. The last one is high-level control system, which is directly related to the control and coordination of the squad. This system allows the player give his squad wider tasks. The uniqueness of this three-level system is in its combination opportunities. Having sent the squad to fight the enemy, you can take a sniper and send him to the flank to support the advancing troops with accurate fire from the cover. As it was said, the squad will act as a whole squad and will not disband while your sniper is going to the specified point.
There is another variant: to keep the squad commander in Direct Control mode. Other squad soldiers would automatically comprehend what target their commander is firing at and would support his fire with theirs. They will follow other actions of their commander exactly like in the common control mode.
It will be possible to apply various control combinations, it gives the player more freedom and the variety of choice. Each player will find the methods, which are mostly convenient and nice for him, we can not advise a universal solution for all players.
7. How did you manage to balance the actions of AI with the player's instructions? Can soldiers disobey the player's orders for example?
This is a very good question. It was difficult to establish a balance between player's orders and AI thinking. Initially we thought that individual decisions and AI actions are nice. With the course of time and in process of testing it turned out that excessive independence of soldiers, staying under player's control, irritates and doesn't let play to full extent. Everything had influence on it, soldiers made decisions to attack on their own, when the player didn't want it or gave themselves out with shots during secret missions. In general they acted as they liked.
So, we understood that only the method of development, which we applied earlier, could help us. This was the "cut and try method" of iterative research and development. We started reducing the initiative of the units controlled by the player. It was important not to deprive them of their senses and not to prohibit them to act at all. It was required to find a nice balance between the player desires and AI plans.
Now the soldiers controlled by the player don't obey player's orders, only if something threatens their life. For example they will not go to a burning house, they run away from flying grenades and from moving vehicles. A squad can defend some time, fight and hide without player's attention, however if enemy forces are surpassing only the player can help soldiers.
8. Are there any emotional aspects the player has to confront with, besides strategic AI? Do the soldiers have senses like fear?
Yes, we needed emotional aspects for soldiers conducted by the complicated AI system, which we developed for 'Faces of War'. This all is transparent for the player, he doesn't see the figures, but he can estimate the morale of soldiers from their behavior. All soldiers have the above-mentioned morale (both enemy AI and player's soldiers). It can change in process of a battle depending on the events happening around the soldier, and opposite, soldiers calm down in quite situations and their morale "gets balanced" so to say. The following influences the morale of soldiers: physical state, health. Additional influence is executed by current injuries, they lower the morale. However soldiers are worried not only by their state, but also by the state of their brothers-in-arms. If a soldier sees that his comrades are dead all around him, it influences his morale as well. The opposite option is fair, keen shots and deaths of enemies boost the morale of soldiers. Effective attacks can encourage soldiers, they would decide then to attack the enemy further. If they encounter their brothers-in-arms, they exchange front news. In this case soldiers with high morale can encourage the tired ones, who lost their hope. The morale of soldiers influences their behavior. In particular the level of activity, they can want to attack the enemy or on the contrary to retreat. The amount of soldiers, allies and their class (heavy armament, AFV, tanks etc) influences the morale of soldiers as well. In this way this complicated system is purposed for one thing - to create a realistic picture of soldier behavior in the battle conditions. We don't operate any figures, percents. Emotions of soldiers are expressed in their behavior and each player would feel it playing in 'Faces of War'.
9. Would you like to say something for the community?
We received a lot of feedbacks and suggestions after the release of 'Soldiers: Heroes of WWII' concerning the system of AI and tried to implement all of them or almost all of them in 'Faces of War'. Therefore the opinion of the community is important for us and we always listen to it.