Backstabbing code!

[tommerbob]

Hello helpers. Its been a while. I'm using a simple function to detect whether a unit is behind another unit:

function Backstab takes unit attacker, unit target returns boolean
    local real casterfacing = GetUnitFacing(attacker)
    local real targetfacing = GetUnitFacing(target)
    if facecaster > (facetarget - 50.) and facecaster < (facetarget + 50.) then
        return true
    endif
    return false
endfunction

And it seems to work, but is there a better/more accurate way to do it?

 

[Dirac]

Indeed there is, I thought of it no more than a few weeks ago.

[ljass]Cos((angle between units) - (facing of target)) >= Cos(50.)[/ljass]

Link to complete code
http://www.hiveworkshop.com/forums/...-code-snippets-40758/index46.html#post2054375

 

[tommerbob]

Hmmm, its not working. This is what I have:

function Cone takes real a, real b, real o returns boolean
     return Cos(b-a)>=Cos(o)
endfunction

function backstab takes unit attacker, unit target returns boolean
     if Cone(GetUnitFacing(attacker),Atan2(GetUnitY(target)-GetUnitY(attacker),GetUnitX(target)-GetUnitX(attacker)),50.) then
          return true 
     endif
     return false
endfunction

Backstab function is returning false. What am I doing wrong?

 

[Dirac]

GetUnitFacing(attacker)

->

GetUnitFacing(target)*bj_DEGTORAD

 

[tommerbob]

Okay I got it working, but your code doesn't detect if a unit is behind another unit, it merely checks if the unit is inside a cone in front of another unit.

Despite that, this is actually really useful, this will help me with several multishot/aoe spells I'm trying to do.

 

[Laiev]

 

[tommerbob]

Edit: nvm.

 

[luorax]

Yep, for facing of the unit use [ljass]360.-GetUnitFacing(target)[/ljass], and switch parameters in the [ljass]Atan[/ljass] call. I think that may solve the problem.

 

[Dirac]

Yep, for facing of the unit use [ljass]360.-GetUnitFacing(target)[/ljass], and switch parameters in the [ljass]Atan[/ljass] call. I think that may solve the problem.

????

To determine if an unit is behind another unit you must know which is the target's unit "field of view" which would be a cone with operture close to 45 degrees from the center (or 90 degrees total) and same facing as the unit's facing angle, then compare the facing of the unit with the angle between the target and the attacker and check if it's inside the given point

[ljass]Cone(GetUnitFacing(target)*bj_DEGTORAD,Atan2(GetUnitY(attacker)-GetUnitY(target),GetUnitY(attacker)-GetUnitY(target)),bj_PI/4)[/ljass]

That would be the best way to do it.
The best thing about using the "Cos" function is that it really doesn't matter if the angle is positive or negative, In any other case you would have to make the angle positive and then compare all 3 possibilities (over 360, between 360 and 0 and below 0)

TL;DR just use the Cone example I wrote above

 

[luorax]

Well, I don't think I can reply to that message, I think I'm lost, my math is too sucky at the moment.