Find nearest enemy unit

[ThySpektre]

I am trying to make an ability fire off when an item is dropped. I want it to target the nearest enemy unit. Any ideas how to find the nearest enemy unit?

ThySpektre

 

[AceHart]

One, but I wouldn't recommend it.
Pick every unit in range, and compare the "distance between points" for each one...

 

[Vexorian]

I would recommend it, as long as you make sure it doesn't have memory leaks it will work.

 

[phyrex1an]

This method is only good if there is a maximum distance but here is a way.

Some variables:
Type - Name
Real - Dist1
Real - Dist2
Point - Point1
Point - Point2
Unit - Closest

You dont need all variables if you dont want but I have used them for easier code and to remove memory leaks

        Set Closest = No unit
        Set Dist1 = 800.00
        Set Point1 = (Position of (Triggering unit))
        Custom script:   set bj_wantDestroyGroup = true
        Unit Group - Pick every unit in (Units within Dist1 of Point1 matching ((((Matching unit) belongs to an enemy of (Owner of (Triggering unit))) Equal to True) and (((Matching unit) is alive) Equal to True))) and do (Actions)
            Loop - Actions
                Set Point2 = (Position of (Picked unit))
                Set Dist2 = (Distance between Point1 and Point2)
                If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                    If - Conditions
                        Dist1 Greater than Dist2
                    Then - Actions
                        Set Dist1 = Dist2
                        Set Closest = (Picked unit)
                    Else - Actions
                Custom script:   call RemoveLocation(udg_Point2)
        Custom script:   call RemoveLocation(udg_Point1)

If Closest = No Unit then there was no enemy unit in range.

 

[pladams9]

This is purely theoretical and does not apply to WC3 in particular, rather any programming situation such as this, but wouldn't it (again theoretically) be faster to search in an in-out direction instead of an out-in direction? That is, instead of looking among a group of units trying to find the closest one, look for the nearest group of units, and find the closest unit among them? For instance taking ever bigger and bigger circles until you come upon one or more units, and see which is the closest out of that group.

Now, I'm not saying this is the best method for this case, but looking at it from a programming perspective, do you think it's a method worth looking into?

Again, it's just an idea.

 

[phyrex1an]

Something like this? I am a little tierd now so there may be some errors. I also think there is a jass script that does this (better) but I cannnot find it now.

    Set Point1 = (Position of (Triggering unit))
    Set Range1 = 999999.00
    Set Closest = No unit
    Set Interval = 50.00
    For each (Integer A) from 1 to 1000, do (Actions)
        Loop - Actions
            Set Current = (Units within (Interval x (Real((Integer A)))) of Point1 matching ((((Matching unit) belongs to an enemy of (Owner of (Triggering unit))) Equal to True) and (((Matching unit) is alive) Equal to True)))
            Unit Group - Remove all units of Done from Current
            Unit Group - Pick every unit in Current and do (Actions)
                Loop - Actions
                    Set Point2 = (Position of (Picked unit))
                    Set Range2 = (Distance between Point1 and Point2)
                    If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                        If - Conditions
                            Range1 Greater than Range2
                        Then - Actions
                            Set Range1 = Range2
                            Set Closest = (Picked unit)
                        Else - Actions
                    Custom script:   call RemoveLocation(udg_Point2)
            Custom script:   call DestroyGroup(udg_Current)
            If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                If - Conditions
                    Closest Not equal to No unit
                Then - Actions
                    Custom script:   exitwhen true
                Else - Actions
            Unit Group - Add all units of Current to Done
    Custom script:   call RemoveLocation(udg_Point1)
    Unit Group - Remove all units from Done

 

[pladams9]

Hmm... I think that's about it, but I'm not sure that it's all necessary. Here's some psuedo-code:

Set Interval = 50

For Integer A = 1 to 1000
Set unitGroup = (Units Within (Interval x Integer A) Matching (Matching Unit is an enemy of (Triggering Unit))
    If - Conditions:
        Number of Units in unitGroup > 0
    Then - Actions:
        Pick Every Unit in unitGroup and Do:
            <Cycle Units to Find Closest Unit>
    Else - Actions:
        Do Nothing

That is of course not exact, and you would have to put in extra custom scripts as you have to prevent leaks, but believe that is mostly correct. You could also replace (Interval x Integer A) with an exponential function of Integer A so that the range would increase more and more, so as to find units more quickly if they are far away.

 

[Heptameron]

There's no point having the If statement there. It'll make the trigger quite a bit slower if there's a big unit group.

But that might be faster, who knows?

 

[pladams9]

Your right. If there aren't any units in the unit group it won't run anyway.

 

[Heptameron]

Your right. If there aren't any units in the unit group it won't run anyway.

And "number of units in unit group" actually uses a "pick every" action along with a global variable to count units anyway.