Pulling a unit to another

[Lehona]

If I just have the X- and Y-coordinates, how would be the function to "pull" unit A to Unit B?

Sorry, but I suck at 2D-Math =D

 

[uberfoop]

I will be refering to the current unit coordinates as XA, YA, XB, and YB. The "coordinate differences" (XB-XA) and (YB-YA) will be refered to as XD and YD.

Alright, first you need to know the direction from unit A to unit B, since that is the direction of pullage. The most straightforward way of getting this value in WC3 is the Atan2 function. [ljass]Atan2(YD,XD)[/ljass] will give you this angle, which I will refer to as Theta, in radians.

You haven't specified how the pulling should happen, so I'm assume it's at some arbitary speed V distance per interval.

//============================================

Given some angle Theta in radians, some distance V that you want the unit to be slid, some unit A, and current unit coordinates XA and YA, the way to move the unit in that direction is:

call SetUnitX(A,XA+Z*Cos(Theta))
call SetUnitY(A,YA+Z*Sin(Theta))

If Z is small, and the intervals in which you do this are fast, the unit will appear to slide in Theta direction.

 

[Lehona]

Is there a way to get the Atan2-value without the function? I know, this is the place for questions about JASS, but I need to do it without Atan2 (In another language, which doesn't provide Atan2) - maybe a formula as an alternative to Atan2?

Anyway, thanks for now (+rep)

 

[uberfoop]

Getting the value of Atan without the Atan function can be done through a variety of ways, but it's a motherfroodlenutzskying pain in the face. For example, you could use its Taylor Series.

However, there is still a way around giving up. It's called not using trigonometric functions at all.

So, again, we have XA, YA, XB, YB, XD, YD.

Our final result should be a vector consisting of an x and a y component which I will refer to as J and K. J will be equal to what Cos(Theta) was and K will be equal to what Sin(Theta) was.

I will define some real R to be R=Sqrt(XD^2 + YD^2)

Now:
J=XD/R
K=YD/R

So, for actually moving the unit, you get:

call SetUnitX(A,XA+Z*J)
call SetUnitY(A,YA+Z*K)

This way you don't bother with the angles at all.

 

[Lehona]

Actually it seems not to work, here is what I've got (its another language, so read the comments^^)

var int herX; herX = her._zCVob_trafoObjToWorld[ 3]; // Get the x of the hero
			var int itemX; itemX = Telekinese_Item._zCVob_trafoObjToWorld[ 3]; // Get the X of the Item (which I want to move)
			var int herZ; herZ = her._zCVob_trafoObjToWorld[11]; // Get the Z of the hero (Y for Warcraft)
			var int itemZ; itemZ = Telekinese_Item._zCVob_trafoObjToWorld[1]; // Get the Z of the Item which I want to move (Y for Warcraft)
			
			var int xd; xd = subf(herx, itemx); // herx - itemx
			var int zd; zd = subf(herz, itemz); // herz - itemz
			
			var int r; r = sqrtf(addf(mulf(xd,xd), mulf(zd,zd))); // sqrt(xd*xd+zd*zd)
			
			var int J; J = divf(xd, r); // xd / r
			var int K; K = divf(zd, r); // zd / r
			
			// y/x
			// Setting new Positions
			Telekinese_Item._zCVob_trafoObjToWorld[ 3] = addf(itemX,mulf(mkf(1), J)); // Setting the Items X position: itemx + 1*J
			Telekinese_Item._zCVob_trafoObjToWorld[11] = addf(itemz, mulf(mkf(1), K)); // Settint the Items Z (Y for Warcraft): itemz + 1*K

Just doesn't work :/

I got an Arctan-Func to work though (Taylor-Series) with some help, can I replace Atan2(y,x) with Arctan(y/x)? And do I have to care about negative quadrants? Some advices for a Cos and a Sin function would be really appreciated...

 

[Romek]

Moved to the Programming Forum. This obviously doesn't belong in JASS Help.

 

[Lehona]

Didn't know we even have one, sorry

 

[Lehona]

Got that Sinus and Cosinus-function to work with the Taylor-Series.

 

[SerraAvenger]

http://en.wikipedia.org/wiki/Atan2