Area of Effect in a rectangle?

[Jazztastic]

Let's say I wanted to do certain effects to all units within a rectangle in front of the caster. How would I go about selecting them?


The red dot is the caster. I want all units in the rectangle to be picked. It's just a crude drawing, I want the concept of how to do this.
View attachment 105312

 

[Maker]

I'm using that kind of thing in this spell: Static Fence

The main thing is this:

// Returns a boolean that tells whether the point is inside a rectangle.
    // (px , py) = Point to check
    // (cx , cy) = lower left corner of the rect
    // (ax , ay) = upper left corner
    // (bx , by) = lower right corner
    function IsPointInRect takes real px , real py , real cx , real cy , real ax , real ay , real bx , real by returns boolean        
        local real dot1 = (px-cx)*(ax-cx) + (py-cy)*(ay-cy)
        local real dot2 = (ax-cx)*(ax-cx) + (ay-cy)*(ay-cy)
        local real dot3 = (px-cx)*(bx-cx) + (py-cy)*(by-cy)
        local real dot4 = (bx-cx)*(bx-cx) + (by-cy)*(by-cy)
        
        return dot1 >= 0 and dot1 <= dot2 and dot3 >= 0 and dot3 <= dot4
    endfunction

 

[Jazztastic]

I understand the general concept, but I'm not understanding how I use it. With the return, how do I use that return in an if/then/else statement?

function IsPointInRect takes real px , real py , real cx , real cy , real ax , real ay , real bx , real by returns boolean

This part also doesn't make sense. The variables were never set, how do they tell whether the unit is inside it or not?

 

[Adiktuz]

Those variables are called parameters, they are sent to the function when you call the function

//I'll use the native function KillUnit as an example:
//this is what the function KillUnit looks like

native KillUnit takes unit whichUnit returns nothing

call KillUnit(GetTriggerUnit())

//on this case, KillUnit takes a unit parameter, so we give it a unit (via the GetTriggerUnit() function) when we call it...

also, the code Maker posted checks the point not the unit... meaning you should feed the function the point where the unit is located so that it can check if the point is within the range (which means the unit is inside the range too)...

 

[WaterKnight]

This does not cover the unit's collision size, though. To count it in, you could find the closest point from a unit to the quadrangle, then use
constant native IsUnitInRangeXY takes unit whichUnit, real x, real y, real distance returns boolean
there with a distance of zero or if you have the collision size, search for intersections of circle and the quadrangle's sides. Of course, this only has do be done in case the unit's origin was not already within.

 

[Jazztastic]

Ok but how are parameters defined? How do I change the dimensions of the created box?

 

[Adiktuz]

It all depends on the value you input when you call the function...

//example

 // (px , py) = Point to check
    // (cx , cy) = lower left corner of the rect
    // (ax , ay) = upper left corner
    // (bx , by) = lower right corner

call IsPointInRect(0.00 , 0.00 , -300.0 , -200.0 , -300 , 200.0 , 300.0 , -200.0)
/*
here, the parameters cx,cy,ax,ay,bx,by defines the created box...

but don't we need to define the upper right corner too? 

or also, we can just check the upper right and the lower left...
*/

 

[Maker]

We don't need to define upper right corner. If we know two vectors that are the sides of a rectangle, and they originate from point P, then we know where the opposite corner will be.

 

[Miles111]

The spell Shockwave is based on what your talking about. In shockwave, Area of Affect = width of rectangle, distance = length. You could use it as your base spell.

 

[baassee]

And shockwave also creates terrain deformations.

 

[Jazztastic]

And shockwave doesn't allow you to add the units to a unitgroup so you can do other stuff with them. I'm not talking about shockwave.

One last question about this. I don't understand, how I tell if the unit is inside the rectangle. Once the rectangle is defined, and we know that the units are inside the rectangle, how do I use that information, will it return a boolean to true, or will they be added to a specified unit group, or what?

 

[baassee]

If you use Maker's function you can check if the position of a unit is inside a rect. It will return true if it is and then the unit should be added to a unit group. Although you have to add it yourself to your group.

 

[Jazztastic]

I looked through Makers spell (static fence) to try to udnerstand this part better, and it looks like the picking of the unit group has to be in JASS : l

I'll make it work

 

[baassee]

It's possible to use jass functions in GUI as well. You'll just need a boolean variable and use custom script set udg_yourboolean = IsPointInRect(all the parameters) and then an if block which just check if the variable is true then...

 

[Jazztastic]

That custom script is really helpful. Thanks for sticking through this with me (I'm a JASS newb)