Historical WWII campaigns
The highly anticipated Faces of War, the World War II squad-based, real-time strategy game is due for release on PC in March 2006.
Ubisoft have sent us the Q & A session with the development team:
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 informa-tion. 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 in-stinct. It helps to make the behavior of soldiers more natural. The units can de-fend 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 diffi-cult 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 im-portant. 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 de-cisions 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 com-municate 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 ap-propriate 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 devel-opments, 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 atten-tion 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 interconnec-tion 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 sol-diers 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 pat-tern behavior of soldiers. This is one of action pattern of soldiers and they can ap-ply 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 vehi-cles (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 simpli-fies 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 lo-cations from which they can shoot more efficiently. Moreover soldiers throw gre-nades 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.