Models the process to capture a Zone for a Coalition, which is guarded by another Coalition.

This is a powerful concept that allows to create very dynamic missions based on the different state transitions of various zones.

In order to use ZONE_CAPTURE_COALITION, you need to:

• Create a Zone object from one of the ZONE_ classes.
  Note that ZONE_POLYGON_ classes are not yet functional.
  The only functional ZONE_ classses are those derived from a ZONE_RADIUS.
• Set the state of the zone. Most of the time, Guarded would be the initial state.
• Start the zone capturing monitoring process.
  This will check the presence of friendly and/or enemy units within the zone and will transition the state of the zone when the tactical situation changed. The frequency of the monitoring must not be real-time, a 30 second interval to execute the checks is sufficient.

Important:

You must start the monitoring process within your code, or there won't be any state transition checks executed.
See further the start/stop monitoring process.

Important:

Ensure that the object containing the ZONE_CAPTURE_COALITION object is persistent. Otherwise the garbage collector of lua will remove the object and the monitoring process will stop. This will result in your object to be destroyed (removed) from internal memory and there won't be any zone state transitions anymore detected! So use the local keyword in lua with thought! Most of the time, you can declare your object gobally.

Example:

  -- Define a new ZONE object, which is based on the trigger zone `CaptureZone`, which is defined within the mission editor.
  CaptureZone = ZONE:New( "CaptureZone" )

  -- Here we create a new ZONE_CAPTURE_COALITION object, using the :New constructor.
  ZoneCaptureCoalition = ZONE_CAPTURE_COALITION:New( CaptureZone, coalition.side.RED )

  -- Set the zone to Guarding state.
  ZoneCaptureCoalition:__Guard( 1 )

  -- Start the zone monitoring process in 30 seconds and check every 30 seconds.
  ZoneCaptureCoalition:Start( 30, 30 ) 

Constructor:

Use the ZONE_CAPTURE_COALITION.New() constructor to create a new ZONE_CAPTURE_COALITION object.

ZONE_CAPTURE_COALITION is a finite state machine (FSM).

ZONE_CAPTURE_COALITION States

• Captured: The Zone has been captured by an other coalition.
• Attacked: The Zone is currently intruded by an other coalition. There are units of the owning coalition and an other coalition in the Zone.
• Guarded: The Zone is guarded by the owning coalition. There is no other unit of an other coalition in the Zone.
• Empty: The Zone is empty. There is not valid unit in the Zone.

2.2 ZONE_CAPTURE_COALITION Events

• Capture: The Zone has been captured by an other coalition.
• Attack: The Zone is currently intruded by an other coalition. There are units of the owning coalition and an other coalition in the Zone.
• Guard: The Zone is guarded by the owning coalition. There is no other unit of an other coalition in the Zone.
• Empty: The Zone is empty. There is not valid unit in the Zone.

"Script It"

ZONE_CAPTURE_COALITION allows to take action on the various state transitions and add your custom code and logic.

Take action using state- and event handlers.

The most important to understand is how states and events can be tailored. Carefully study the diagram and the explanations.

State Handlers capture the moment:

• On Leave from the old state. Return false to cancel the transition.
• On Enter to the new state.

Event Handlers capture the moment:

• On Before the event is triggered. Return false to cancel the transition.
• On After the event is triggered.

Each handler can receive optionally 3 parameters:

• From: A string containing the From State.
• Event: A string containing the Event.
• To: A string containing the To State.

The mission designer can use these values to alter the logic. For example:

--- @param Functional.ZoneCaptureCoalition#ZONE_CAPTURE_COALITION self
function ZoneCaptureCoalition:OnEnterGuarded( From, Event, To )
  if From ~= "Empty" then
    -- Display a message
  end
end

This code checks that when the Guarded state has been reached, that if the From state was Empty, then display a message.

Example Event Handler.

--- @param Functional.ZoneCaptureCoalition#ZONE_CAPTURE_COALITION self
function ZoneCaptureCoalition:OnEnterGuarded( From, Event, To )
  if From ~= To then
    local Coalition = self:GetCoalition()
    self:E( { Coalition = Coalition } )
    if Coalition == coalition.side.BLUE then
      ZoneCaptureCoalition:Smoke( SMOKECOLOR.Blue )
      US_CC:MessageTypeToCoalition( string.format( "%s is under protection of the USA", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
      RU_CC:MessageTypeToCoalition( string.format( "%s is under protection of the USA", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
    else
      ZoneCaptureCoalition:Smoke( SMOKECOLOR.Red )
      RU_CC:MessageTypeToCoalition( string.format( "%s is under protection of Russia", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
      US_CC:MessageTypeToCoalition( string.format( "%s is under protection of Russia", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
    end
  end
end

Stop and Start the zone monitoring process.

At regular intervals, the state of the zone needs to be monitored. The zone needs to be scanned for the presence of units within the zone boundaries. Depending on the owning coalition of the zone and the presence of units (of the owning and/or other coalition(s)), the zone will transition to another state.

However, ... this scanning process is rather CPU intensive. Imagine you have 10 of these capture zone objects setup within your mission. That would mean that your mission would check 10 capture zones simultaneously, each checking for the presence of units. It would be highly CPU inefficient, as some of these zones are not required to be monitored (yet).

Therefore, the mission designer is given 2 methods that allow to take control of the CPU utilization efficiency:

• ZONE_CAPTURE_COALITION.Start(): This starts the monitoring process.
• ZONE_CAPTURE_COALITION.Stop(): This stops the monitoring process.

IMPORTANT

Each capture zone object must have the monitoring process started specifically. The monitoring process is NOT started by default!!!

Full Example

The following annotated code shows a real example of how ZONE_CAPTURE_COALITION can be applied.

The concept is simple.

The USA (US), blue coalition, needs to capture the Russian (RU), red coalition, zone, which is near groom lake.

A capture zone has been setup that guards the presence of the troops. Troops are guarded by red forces. Blue is required to destroy the red forces and capture the zones.

At first, we setup the Command Centers

 do

   RU_CC = COMMANDCENTER:New( GROUP:FindByName( "REDHQ" ), "Russia HQ" )
   US_CC = COMMANDCENTER:New( GROUP:FindByName( "BLUEHQ" ), "USA HQ" )

 end

Next, we define the mission, and add some scoring to it.

 do -- Missions

   US_Mission_EchoBay = MISSION:New( US_CC, "Echo Bay", "Primary",
     "Welcome trainee. The airport Groom Lake in Echo Bay needs to be captured.\n" ..
     "There are five random capture zones located at the airbase.\n" ..
     "Move to one of the capture zones, destroy the fuel tanks in the capture zone, " ..
     "and occupy each capture zone with a platoon.\n " .. 
     "Your orders are to hold position until all capture zones are taken.\n" ..
     "Use the map (F10) for a clear indication of the location of each capture zone.\n" ..
     "Note that heavy resistance can be expected at the airbase!\n" ..
     "Mission 'Echo Bay' is complete when all five capture zones are taken, and held for at least 5 minutes!"
     , coalition.side.RED )

   US_Mission_EchoBay:Start()

 end

Now the real work starts. We define a CaptureZone object, which is a ZONE object. Within the mission, a trigger zone is created with the name CaptureZone, with the defined radius within the mission editor.

 CaptureZone = ZONE:New( "CaptureZone" )

Next, we define the ZoneCaptureCoalition object, as explained above.

 ZoneCaptureCoalition = ZONE_CAPTURE_COALITION:New( CaptureZone, coalition.side.RED ) 

Of course, we want to let the ZoneCaptureCoalition object do something when the state transitions. Do accomodate this, it is very simple, as explained above. We use Event Handlers to tailor the logic.

Here we place an Event Handler at the Guarded event. So when the Guarded event is triggered, then this method is called! With the variables From, Event, To. Each of these variables containing a string.

We check if the previous state wasn't Guarded also. If not, we retrieve the owning Coalition of the ZoneCaptureCoalition, using self:GetCoalition(). So Coalition will contain the current owning coalition of the zone.

Depending on the zone ownership, different messages are sent. Note the methods ZoneCaptureCoalition:GetZoneName().

 --- @param Functional.ZoneCaptureCoalition#ZONE_CAPTURE_COALITION self
 function ZoneCaptureCoalition:OnEnterGuarded( From, Event, To )
   if From ~= To then
     local Coalition = self:GetCoalition()
     self:E( { Coalition = Coalition } )
     if Coalition == coalition.side.BLUE then
       ZoneCaptureCoalition:Smoke( SMOKECOLOR.Blue )
       US_CC:MessageTypeToCoalition( string.format( "%s is under protection of the USA", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
       RU_CC:MessageTypeToCoalition( string.format( "%s is under protection of the USA", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     else
       ZoneCaptureCoalition:Smoke( SMOKECOLOR.Red )
       RU_CC:MessageTypeToCoalition( string.format( "%s is under protection of Russia", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
       US_CC:MessageTypeToCoalition( string.format( "%s is under protection of Russia", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     end
   end
 end

As you can see, not a rocket science. Next is the Event Handler when the Empty state transition is triggered. Now we smoke the ZoneCaptureCoalition with a green color, using self:Smoke( SMOKECOLOR.Green ).

 --- @param Functional.Protect#ZONE_CAPTURE_COALITION self
 function ZoneCaptureCoalition:OnEnterEmpty()
   self:Smoke( SMOKECOLOR.Green )
   US_CC:MessageTypeToCoalition( string.format( "%s is unprotected, and can be captured!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
   RU_CC:MessageTypeToCoalition( string.format( "%s is unprotected, and can be captured!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
 end

The next Event Handlers speak for itself. When the zone is Attacked, we smoke the zone white and send some messages to each coalition.

 --- @param Functional.Protect#ZONE_CAPTURE_COALITION self
 function ZoneCaptureCoalition:OnEnterAttacked()
   ZoneCaptureCoalition:Smoke( SMOKECOLOR.White )
   local Coalition = self:GetCoalition()
   self:E({Coalition = Coalition})
   if Coalition == coalition.side.BLUE then
     US_CC:MessageTypeToCoalition( string.format( "%s is under attack by Russia", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     RU_CC:MessageTypeToCoalition( string.format( "We are attacking %s", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
   else
     RU_CC:MessageTypeToCoalition( string.format( "%s is under attack by the USA", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     US_CC:MessageTypeToCoalition( string.format( "We are attacking %s", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
   end
 end

When the zone is Captured, we send some victory or loss messages to the correct coalition. And we add some score.

 --- @param Functional.Protect#ZONE_CAPTURE_COALITION self
 function ZoneCaptureCoalition:OnEnterCaptured()
   local Coalition = self:GetCoalition()
   self:E({Coalition = Coalition})
   if Coalition == coalition.side.BLUE then
     RU_CC:MessageTypeToCoalition( string.format( "%s is captured by the USA, we lost it!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     US_CC:MessageTypeToCoalition( string.format( "We captured %s, Excellent job!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
   else
     US_CC:MessageTypeToCoalition( string.format( "%s is captured by Russia, we lost it!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
     RU_CC:MessageTypeToCoalition( string.format( "We captured %s, Excellent job!", ZoneCaptureCoalition:GetZoneName() ), MESSAGE.Type.Information )
   end

   self:__Guard( 30 )
 end

And this call is the most important of all! In the context of the mission, we need to start the zone capture monitoring process. Or nothing will be monitored and the zone won't change states. We start the monitoring after 5 seconds, and will repeat every 30 seconds a check.

 ZoneCaptureCoalition:Start( 5, 30 )