[Solved] Unit Group in Chain Lightning

[akaiharuki]

Hello, I've simulated the animation of Chain Lightning with the following trigger:
(This is just part of the triggers, and it is not MUI but I'll add it later)

Hidden

• Chain Lightning cast
  • Events
    • Unit - A unit Starts the effect of an ability
  • Conditions
    • (Ability being cast) Equal to Chain Lightning
  • Actions
    • Set CLCaster[0] = (Triggering unit)
    • Set CLTarget[0] = (Target unit of ability being cast)
    • Set CLAoE[0] = (750.00 + (100.00 x (Real((Level of (Ability being cast) for (Triggering unit))))))
    • Set CLPoint[0] = (Position of (Target unit of ability being cast))
    • Set CLPoint[1] = (Position of (Triggering unit))
    • Set CLTimer[0] = 0.00
    • Set CLTimer[1] = 10.00
    • Set CLLightningCount[0] = 0
    • Set CLDamage[0] = (10.00 + (5.00 x (Real((Level of (Ability being cast) for (Triggering unit))))))
• ------------------------------------------------------------------------------------------------------------------
• ------------------------------------------------------------------------------------------------------------------
  • Unit Group - Add (Triggering unit) to CLGroup[3]
  • Lightning - Create a Chain Lightning effect from source CLPoint[1] to target CLPoint[0]
  • Set CLLightning[CLLightningCount[0]] = (Last created lightning effect)
  • Unit Group - Add CLTarget[0] to CLGroup[3]
  • Custom script: call RemoveLocation(udg_CLPoint[0])
  • Custom script: call RemoveLocation(udg_CLPoint[1])
  • Trigger - Turn on Chain Lightning bounce <gen>

• Chain Lightning bounce
  • Events
    • Time - Every 0.25 seconds of game time
  • Conditions
  • Actions
    • Set CLPoint[0] = (Position of CLTarget[CLLightningCount[0]])
    • Set CLCount = 0
    • Set CLGroup[0] = (Units within CLAoE[0] of CLPoint[0])
    • Unit Group - Pick every unit in CLGroup[0] and do (Actions)
      • Loop - Actions
        • If (All Conditions are True) then do (Then Actions) else do (Else Actions)
          • If - Conditions
            • ((Picked unit) is in CLGroup[3]) Equal to False
          • Then - Actions
            • Unit Group - Add (Picked unit) to CLGroup[2]
          • Else - Actions
    • Set CLGroup[1] = (Random 1 units from CLGroup[2])
    • Unit Group - Pick every unit in CLGroup[1] and do (Actions)
      • Loop - Actions
        • Unit Group - Add (Picked unit) to CLGroup[3]
        • Set CLCount = (CLCount + 1)
        • Set CLPoint[1] = (Position of (Picked unit))
        • Set CLLightningCount[0] = (CLLightningCount[0] + 1)
        • Set CLTarget[CLLightningCount[0]] = (Picked unit)
    • Unit Group - Remove all units of CLGroup[2] from CLGroup[2]
    • If (All Conditions are True) then do (Then Actions) else do (Else Actions)
      • If - Conditions
        • CLCount Equal to 0
      • Then - Actions
        • Trigger - Turn off (This trigger)
      • Else - Actions
        • Lightning - Create a Chain Lightning effect from source CLPoint[0] to target CLPoint[1]
        • Set CLLightning[CLLightningCount[0]] = (Last created lightning effect)
    • Custom script: call RemoveLocation(udg_CLPoint[0])
    • Custom script: call RemoveLocation(udg_CLPoint[1])
    • Custom script: call DestroyGroup(udg_CLGroup[0])
    • Custom script: call DestroyGroup(udg_CLGroup[1])

But I don't understand why if I add the following lines in between two lines of dash in the first trigger it will not add any unit into CLGroup[3] (store already hit targets so it will not bounce to them again) and it will run endlessly:

Hidden

• Set CLGroup[2] = (Units within CLAoE[0] of CLPoint[0])
• Set CLGroup[3] = CLGroup[2]
• Unit Group - Remove all units of CLGroup[2] from CLGroup[2]
• Unit Group - Remove all units of CLGroup[3] from CLGroup[3]

As I think if I don't set a Unit Group it will leak, so I created 2 groups, then emptied these groups to store units.

 

[Nichilus]

First of all, the following

• Unit Group - Remove all units of CLGroup[2] from CLGroup[2]

can be replaced by a better function:

• Unit Group - Remove all units from CLGroup[2].

The reason why your trigger runs endlessly is because of the following line:

• Set CLGroup[3] = CLGroup[2]

Variables store references to created objects (except for base types like integers, reals, booleans, but basically everything else is a reference).
So you did this:

• Set CLGroup[2] = (Units within CLAoE[0] of CLPoint[0])

which creates a unit group and assigns a reference to this object into variable CLGroup[2].
Then you do

• Set CLGroup[3] = CLGroup[2]

which assign the reference of CLGroup[2] to CLGroup[3]. So at this point, both CLGroup[2] and CLGroup[3] point to same object - to same unit group.

In your 'bounce' trigger you check the following condition:

• ((Picked unit) is in CLGroup[3]) Equal to False

but also do

• Unit Group - Remove all units of CLGroup[2] from CLGroup[2]

Since CLGRoup[2] adn CLGroup[3] reference same unit group, you basically just clear CLGroup[3], meaning the condition will always pass, leading to endless bounces.

 

[akaiharuki]

Thanks so much!

But is there a way to create an Empty Unit Group like I can set a unit variable to No unit so it will not point to any objects at the beginning? Or is the Unit Group in an array empty by default so I just add and remove units in it?

 

[Nichilus]

By default, a unit group variable has an empty unit group assigned to it. You can see it even in the variable's configuration: For variable of type "unit group" its initial value says "Empty Unit Group (Default)".
For unit group array variables, the number of pre-created unit groups matches the number in "Size" option.
So if I create a unit group array variable called "MyGroups" and set it with Size: 3, then the pre-created unit groups will be in:

• MyGroups[1]
• MyGroups[2]
• MyGroups[3]

There is no GUI action to create a new unit group, however you can use custom script to do that:

• Custom script: set udg_<variable_name> = CreateGroup()

Any variable created in GUI trigger editor must be prefixed with "udg_" in custom script. Let's say I want to create a new unit group and assign it to MyGroups array variable under index 8, I would use the following custom script:

• Custom script: set udg_MyGroups[8] = CreateGroup()