Creating units on non-visible areas

[GreeN!X]

Hey! you might not understand the title so here's a bit of an explanation on what I want to do.

I wanted to make a spell that will be able to target an enemy unit. The effect would be that the target unit, upon being buffed by the spell, will be periodically bombarded by suicidal ghosts that appear from the shadows.

Basically, I want to create units on areas that are not visible to enemies, allies or the target itself, and then order it to move towards the target and self destruct. (like using KABOOM on the target unit) These created units will not provide vision to its owner and the spell should be MUI.

So could you guys give me any idea on how I should be able to do the unit creation part? I have absolutely no idea how to start making such a spell.

 

[PurplePoot]

Every so often, pick random points and check if they're visible with the boolean comparison "Visibility - Point Visible to Player".

 

[LordDz]

Give them permanent invisiblity when spawning that you remove after a few seconds?

 

[Zwiebelchen]

You can use this snippet to check if a coordinate is visible.
http://www.hiveworkshop.com/forums/submissions-414/snippet-ispointvisible-249573/#post2501474


A possible approach to this

function CreateRandomSuicideUnit takes integer unitID, unit target, player owner returns unit
   local unit u = CreateUnit(unitID, owner, GetUnitX(target), GetUnitY(target), 0)
   local integer i = 0
   call SetUnitPosition(u, GetUnitX(u)+GetRandomReal(-3000, 3000), GetUnitY(u)+GetRandomReal(-3000,3000))
   loop
      if IsUnitVisible(u, GetOwningPlayer(target)) then
         call SetUnitPosition(u, GetUnitX(u)+GetRandomReal(-3000, 3000), GetUnitY(u)+GetRandomReal(-3000,3000))
      else
         exitwhen true
      endif
      exitwhen i > 20
      set i = i + 1
   endloop
   return u
endfunction

When you use this function, it should create the unit outside of visibility in most cases. However, there's a slight chance the unit will spawn within sight (as it only tries 20 times to find a spot).

You still need to order the unit to attack or use your kaboom ability; this will only handle the spawning.

 

[GreeN!X]

Every so often, pick random points and check if they're visible with the boolean comparison "Visibility - Point Visible to Player".

You can use this snippet to check if a coordinate is visible.
http://www.hiveworkshop.com/forums/submissions-414/snippet-ispointvisible-249573/#post2501474


A possible approach to this

function CreateRandomSuicideUnit takes integer unitID, unit target, player owner returns unit
   local unit u = CreateUnit(unitID, owner, GetUnitX(target), GetUnitY(target), 0)
   local integer i = 0
   call SetUnitPosition(u, GetUnitX(u)+GetRandomReal(-3000, 3000), GetUnitY(u)+GetRandomReal(-3000,3000))
   loop
      if IsUnitVisible(u, GetOwningPlayer(target)) then
         call SetUnitPosition(u, GetUnitX(u)+GetRandomReal(-3000, 3000), GetUnitY(u)+GetRandomReal(-3000,3000))
      else
         exitwhen true
      endif
      exitwhen i > 20
      set i = i + 1
   endloop
   return u
endfunction

When you use this function, it should create the unit outside of visibility in most cases. However, there's a slight chance the unit will spawn within sight (as it only tries 20 times to find a spot).

You still need to order the unit to attack or use your kaboom ability; this will only handle the spawning.

Oh right, I forgot about that function. Though I still need to narrow it down to creating the unit within 1000 area of the target. Thanks. ^^

Zwiebelchen, I only understand a fraction of that thing but I'll try. ^^

Give them permanent invisiblity when spawning that you remove after a few seconds?

I wanted to give the illusion that the units are from somewhere at first then just move towards the target. I don't want them to appear from nothing out of nowhere. Thanks for trying though.

 

[Dr Super Good]

Units can have up to 1800 (or was it 1600?) sight radius if I recall. Checking within that will mostly fail, especially if the unit is air based.

How I would do it...

Pick a random angle.
For every point 128 units apart towards the random angle from the victim unit up to 2400 units.
    If point is visible create ghost, do whatever and stop executing.

Repeat the above a couple of times if it fails but do be aware such tests are likely expensive so the numbed of tries should be small. Instead of a fully random angle, you could spread them out a bit based on the number of tries so that they are more distributed (no chance that it will repeat trying the same angle).

The optimum approach would be to brute force testing all tiles around the target in a staggered fashion to distribute computational load. This could potentially give optimum results, finding even the smallest unseen area such as behind a tree with relative ease.

 

[Zwiebelchen]

I don't think it matters a lot if a unit spawns a little bit farther away or if there is one out of fifty units that spawns in a visible area.
So an approach based on random creep placement like the example I posted is probably the easiest and most performant.