You may have asked yourself what's the use of the game logic units. Most mission designers use it to get positions on the map (eg. Position = GetPos NameOfTheGameLogic).
But the game logic units have a much higher potential! You can use them to implement complex conditions to your missions without using any scripting. But you have to understand the behaviour of game logics:
1. Game logics have a position and can activate triggers just like any other units. Take a look at the condition box of a trigger. There you will find the option "game logic present". You can also group the game logic and the trigger and set the condition to "vehicle present". In this case the trigger will only be activated by the presense of this game logic.
2. You can define waypoints for a game logic unit. The waypoint type can be AND or OR (unlike the waypoints for a 'regular' unit that can be MOVE, HOLD, SEEK AND DESTROY etc.). I'll come to the waypoint type later. As soon as the mission starts, the game logic will go from waypoint to waypoint. But unlike all other units the game logic will not move to the waypoint but 'jump' immediately to it's position.
3. Like for all other waypoints you can define a condition, a timeout and an OnActivation code for a game logic waypoint. When a game logic reaches a waypoint it will perform these actions (in this order):
Wait until the condition is TRUE
Wait until the timeout is passed
Execute the OnActivation code
Jump to the next waypoint
4. Like all waypoints you can synchronize a game logic waypoint with a trigger. That means that the game logic will not proceed to the next waypoint until the trigger condition is TRUE. Now we'll return to the type of the game logic waypoint (AND or OR). If you synchronize more than one trigger with the waypoint, the behaviour of the trigger will depend on the waypoint type. If it is an AND waypoint, the game logic will only jump to the next waypoint when all triggers are activated. If it is an OR waypoint it will proceed to the next waypoint when any of the triggers is activated.
5. Like all other waypoints you can also synchronize a game logic waypoint with any other waypoint. The game logic and the other unit will not proceed to their next waypoints until both of them have reached the synchronized waypoint. This is absolutely the same behaviour as if you would synchronize two non-game logic units. Of course you can also synchronize two game logic waypoints.
But what is that all good for? I'll give you some examples showing the whole potential of game logic units:
Example 1: Establishing radio conversations
To establish a radio conversation you would probably write a script that would look like this:
Alpha1 SideRadio "Message1"
~5
Bravo1 SideRadio "Message2"
~8
Alpha1 SideRadio "Message3"
Without a script you would do it like this:
You'd create a game logic and four waypoints
You'd synchronize the first WP with the trigger that will start the conversation
In the second WP's OnActivation field you'd write: Alpha1 SideRadio "Message1"
In the third WP's OnActivation field you'd write: Bravo1 SideRadio "Message2". Since this radio message has to be sent five seconds after the first, you'd set the timeout to five seconds
In the fourth WP's OnActivation field you'd write: Alpha1 SideRadio "Message3". You'd set the timeout to eight seconds.
As you can see, we can use the timeout of the game logic WPs to time events without having to call a script. While the timeout is equivalent to the ~-operator, the condition field is equivalent to the @-operator.
You can use this method also to create cutscenes without any scripting. In the attachment you will find an example mission that demonstrates a cutscene (radio Alpha) and a radio conversation (radio Bravo).
Example 2: Combining triggers to complex condtions
Now it's going to be a little more complex. What if you had three triggers. The third trigger should be activated if one of the two other triggers are activated. You could also express it like this:
Trigger3 = Trigger1 OR Trigger2 [do not use this syntax in OFP, it's just to describe the boolean correlation of the triggers]
To achieve that you can use a game logic unit:
Create a game logic and define two waypoints. Place the first waypoint outside the third trigger's area and the second one inside the area.
Set the first waypoint's type to OR.
Synchronize the first and the second trigger with the first (OR) waypoint
Draw a group line [F2] between the game logic and the third trigger. Set the trigger's condition to "vehicle present"
The whole thing will work like this: At the beginning of the mission, the game logic will jump to it's first waypoint. Since it's outside of the third trigger's area, it doesn't activate it. The game logic will wait at this OR-waypoint until either the first or the second trigger will be activated. As soon as this happens, the game logic will jump to it's next waypoint. This waypoint is inside the area of the third trigger and so it will be activated. That will cause exactly the effect we wanted.
Finally, let's get really advanced. This time you have four triggers. The fourth trigger should be activated on this condition:
Trigger4 = (Trigger1 OR Trigger2) AND Trigger3
Let's go to work:
Create a game logic, define two waypoints. The first one must be an AND waypoint. The second waypoint must be inside the area of Trigger4. Group Trigger4 and the game logic and set the trigger condition to "vehicle present". This is all similar to above (except that we now use an AND waypoint).
Synchronize Trigger3 with the first waypoint of the game logic.
Create a second game logic with two waypoints. Set the first waypoint to OR. Synchronize the second waypoint with the first waypoint of the other game logic.
Synchronize Trigger1 and Trigger2 with the first (OR) waypoint of this game logic.
But how the hell does this work?
The second game logic will proceed to it's second waypoint if either Trigger1 or Trigger2 is activated. That's the same as above. You could also say:
GameLogic2ReachedWaypoint = Trigger1 OR Trigger2
The first game logic will reach it's second waypoint and activate Trigger4 when Trigger3 is true and the second game logic has reached it's second waypoint:
Trigger4 = GameLogic2ReachedWaypoint AND Trigger3
If you combine these expressions, you'll get:
Trigger4 = (Trigger1 OR Trigger2) AND Trigger3
Voilà!
You can even create more complex condtions in your mission when you combine three or more game logics.
