The basic method for creating an AI is to include something like the following in a function:
NewObject("Sam", Herc, 21 );
This would create a Goad with an object name of "Sam." This object name never really has to come into play, and shows up primarily in the object list. Herc, right after "Sam", indicates the type of object being created. The two we should be concerned about in this lesson are Herc and Tank. The difference should be self-explanator, but be sure to get them right -- if you get them mixed up, then the server will crash the first time it tries to create a HERC that the script calls a tank, or vice versa.
The last number, 21, indicates the ID number of the unit being created. These can be found by extracting datVehicle.cs out from scripts.vol, but for convenience, the entire list is reproduced here (with some added comments):
In any case, it's usual to modify that original function slightly, to something like
%herc = NewObject("Sam", Herc, 21 );
This allows us to manipulate the new HERC more easily. Since the new HERC spawns in at map coordinates (0, 0, 0), we often call a function like setPosition() or warp() to put a new unit where we want it right after it spawns. For instance:
Not all of these will work in multiplayer, however, as some orders are particular to the single-player campaigns.
SetPilot() deserves more discussion. You don't need to use setPilot(), since any new vehicle will have a default profile assigned to it, but it's useful for customizing your AI units. Before you spawn the AI, outside of any functions, you normally include a pilot profile, which looks like
You need to include the word Pilot at the beginning, followed by a name for the profile (which won't show up in the game, only in the script). Also notice the semicolon after the closing curly bracket.
Each AI profile you create must have a unique id, or else the last one will over overwrite any earlier ones with the same number. Skill, accuracy and aggressiveness are what they sound like. activateDist determines how far away an AI will detect a player (I don't think there's any way to bind this to the in-game radar profiles, unfortunately), and deactivateBuff is the distance at which an AI will break off from chasing a target. TargetFreq determines how often an AI looks for a new target (set it too high, and it will barrel singlemindedly at its first target and ignore any others that start firing on it). I'm not certain what trackfreq does. fireFreq determines the rate of weapons fire for the pilot, and LOSFreq affects how often the AI will try to shoot through solid objects. The name is the one that shows up on the overhead map or in the HUD if the AI has been scanned or is on the same team. (If an enemy AI has not been scanned, it will be listed by the name of its vehicle, instead).
An interesting phenomenon is that these pilot properties can be accessed and altered by the profile name (e.g., in the above example, Deathgod) with dot operators. Echo(Deathgod.name) will return "Yama" -- note the absence of a percent or dollar sign in front of Deathgod. I'm not entirely certain how or why this works, but it does. Once setPilot() is run on an AI unit, however, the properties stick to it, and stay put even if the pilot profile is changed. You can alter a vehicle's pilot properties after setPilot() only be running another setPilot() on it. This also means, however, that you can create different pilots using just one profile. The following script is such an example. Whenever a player spawns into the game, an AI pilot is cloned from the player's vehicle, ordered to guard him, and comes equipped with the name Mecha-(player name). For instance, if I jump in this game, my AI pilot will be called Mecha-Orogogus.