7. AI tree

7.1 The tree

The leaves of this tree represent actions the bot can perform. Mostly these actions deal with moving towards a nearby goal.
A leaf has a procedure which gives the bot the ability to perform the specific action. This procedure uses several elementary actions like "moving towards a goal", "aiming at an enemy", "shooting" etc.
The actions represented by the leaves of the tree are fully separate. For instance a bot can't chase and retreat at the same time. As a result the bot always executes only one of the procedures of a leaf at a time. However, it is possible to change from one leaf to another. In other words the bot is able to stop the current action and start another. Changing from one leaf to another is done by following the paths in the tree. When a node is encountered certain settings are initialized.
 

7.2 The leaves

The procedures of all the leaves used in the AI tree of the bot are described below. There is a description of the action(s) the bot will perform followed by the conditions for changes to other leaves.
 

Battle fight

The bot will fight with the enemy. Attack movements will be performed to confuse the enemy and to make it difficult for the enemy to aim. The bot will also aim and try to shoot at the enemy.

• If the bot kills the enemy and wants to type a chat message, it will change to the "stand" leaf.
• When the enemy just died or the bot killed it and doesn't want to type a chat message, it will change to the "seek long term goal" leaf.
• The bot looks around for nearby items that are useful. When such an item is found, the bot will change to the "battle get item" leaf.
• When the bot wants to retreat, it will change to the "battle retreat" leaf.
• When the bot can't see the enemy anymore and wants to chase, it will change to the "battle chase" leaf.
• When the bot doesn't want to chase and the enemy isn't visible, it will change to the "seek long term goal" leaf.

The bot will fight with the enemy. Attack movements will be performed to confuse the enemy and to make it difficult for the enemy to aim. The bot will also aim and try to shoot at the enemy.

• If the bot kills the enemy and wants to type a chat message, it will change to the "stand" leaf.
• When the enemy just died or the bot killed it and doesn't want to type a chat message, it will change to the "seek long term goal" leaf.
• The bot looks around for nearby items that are useful. When such an item is found, the bot will change to the "battle get item" leaf.
• When the bot doesn't want to retreat anymore (for instance it picked up some nice items), it will change to the "battle fight" leaf.
• As soon as the bot can't see the enemy, it will change to the "seek long term goal" leaf.

In this leaf the bot has a chase goal, an enemy that it can't see. The bot follows waypoints leading towards the enemy.

• When the enemy dies during the chase, the bot will change to the "seek long term goal" leaf.
• As soon as the bot can see the enemy, it will change to the "battle fight" leaf.
• The bot looks around for nearby items that are useful. When such an item is found, the bot will change to the "battle get item" leaf.
• The bot also looks around for other nearby enemies. When an enemy is found the bot will fight this new enemy. The bot will change to the "battle fight" leaf.
• When the bot doesn't want to chase anymore (the bot could be hurt during the chase) it will change to the "seek long term goal" leaf.
• When the bot looses track of the enemy it will change to the "seek long term goal" leaf.

In this leaf the bot has a retreat goal. The bot will follow waypoints to get as far away as possible from the enemy. The bot will also aim and try to shoot at the enemy during the retreat. When the enemy the bot is retreating from isn't visible anymore the bot will look around for other enemies and take a new enemy when found.

• If the bot kills the enemy and wants to type a chat message, it will change to the "stand" leaf.
• When the enemy just died or the bot killed it and doesn't want to type a chat message, it will change to the "seek long term goal" leaf.
• The bot looks around for nearby items that are useful. When such an item is the bot will change to the "battle get item" leaf.
• If the enemy isn't visible for a while and there are no other enemies around, the bot will change to the "seek long term goal" leaf. When the enemy isn't visible and there is another nearby enemy, the bot will retreat from this new enemy.
• When the bot is "feeling" better (for instance it has picked up several nice items) and doesn't want to retreat anymore, it will change to the "battle chase" leaf.
• When the bot is taking to long to retreat or simply isn't able to retreat (for instance walked into a dead end) and the enemy isn't visible, the bot will change to the "seek long term goal" leaf. However when the enemy is still visible, the bot will change to the "battle suicidal fight" leaf.

The bot will move towards a nearby item during the battle. The bot will also aim and try to shoot at the enemy.

• If the bot kills the enemy and wants to type a chat message, it will change to the "stand" leaf.
• When the enemy just died or the bot killed it and doesn't want to type a chat message, it will change to the "seek long term goal" leaf.
• When the item has been picked up, the bot will change back to the previous leaf of the AI tree (one of the battle leaves).

In this leaf the bot travels towards a normal long term goal, walkabout goal or a sound goal. The bot moves towards a waypoint that is leading to the long term goal. When at a certain point the bot can't find any more waypoints leading to the long term goal it will use a roam goal. When the long term goal has become invalid for some reason (for instance the bot used to many roam goals) or it is reached,  the bot chooses a new normal long term goal. When no such a goal is found the bot chooses a walkabout goal.  When the bot has a walkabout goal it continuously listens to sounds from possible enemies. When a sound is heard and could be located the bot will take the position of the sound as new long term goal.

• During the travel the bot keeps looking for nearby enemies. When an enemy is found, the bot will change to the "battle fight" leaf.
• When the bot wants to type a random chat message, it will change to the "stand" leaf.
• The bot looks around for reachable items or structural system it wants to use. When something the like is found, the bot will change to the "seek get item" leaf.

The bot will move towards a nearby item or nearby structural system. During the movement towards the item the bot looks around for more interesting items or structural systems that have become reachable. When something is found the bot will take the new item or structural system as nearby goal.

• The bot looks around for nearby enemies. When an enemy is found, the bot will change to the "battle get item" leaf.
• The bot will move towards the nearby goal until the item is picked up or the structural system is reached or activated. Then the bot will return to the "seek long term goal" leaf.

This leaf is used, when the bot just enters the game, respawns or when it types a message. When the bot enters the game or respawns, it stands for a very short moment and doesn't do anything. When the bot has decided to type a chat message, it will also use the "stand" leaf. Before changing to the "stand" leaf, the bot has chosen one of the predefined chat messages and knows an estimate period of time a human would take typing the message. The bot just stands for this period of time and enters the message when the time has lapsed.

• The bot will look around for nearby enemies. When an enemy is found, the bot will change to the "battle fight" leaf.
• When the time has lapsed the bot will change to the "seek long term goal" leaf.

In this leaf the bot isn't doing anything. The intermission is at the end of a game. The players can see the score and after a short period of time the game restarts. During the intermission a player can't do anything and the bots also won't try to do anything.